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  • Wiley  (309,950)
  • American Institute of Physics  (187,789)
  • American Geophysical Union  (72,006)
  • 2010-2014  (276,674)
  • 1995-1999  (155,328)
  • 1990-1994  (137,743)
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  • 101
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    Detecting young, slow‐slipping active faults by geologic and multidisciplinary high‐resolution geophysical investigations: A case study from the Apennine seismic belt, Italy. (2010)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The Southern Apennines range of Italy presents significant challenges for active fault detection due to the complex structural setting inherited from previous contractional tectonics, coupled to very recent (Middle Pleistocene) onset and slow slip rates of active normal faults. As shown by the Irpinia Fault, source of a M6.9 earthquake in 1980, major faults might have small cumulative deformation and subtle geomorphic expression. A multidisciplinary study including morphological-tectonic, paleoseismological, and geophysical investigations has been carried out across the extensional Monte Aquila Fault, a poorly known structure that, similarly to the Irpinia Fault, runs across a ridge and is weakly expressed at the surface by small scarps/warps. The joint application of shallow reflection profiling, seismic and electrical resistivity tomography, and physical logging of cored sediments has proved crucial for proper fault detection because performance of each technique was markedly different and very dependent on local geologic conditions. Geophysical data clearly (1) image a fault zone beneath suspected warps, (2) constrain the cumulative vertical slip to only 25–30 m, (3) delineate colluvial packages suggesting coseismic surface faulting episodes. Paleoseismological investigations document at least three deformation events during the very Late Pleistocene (〈20 ka) and Holocene. The clue to surface-rupturing episodes, together with the fault dimension inferred by geological mapping and microseismicity distribution, suggest a seismogenic potential of M6.3. Our study provides the second documentation of a major active fault in southern Italy that, as the Irpinia Fault, does not bound a large intermontane basin, but it is nested within the mountain range, weakly modifying the landscape. This demonstrates that standard geomorphological approaches are insufficient to define a proper framework of active faults in this region. More in general, our applications have wide methodological implications for shallow imaging in complex terrains because they clearly illustrate the benefits of combining electrical resistivity and seismic techniques. The proposed multidisciplinary methodology can be effective in regions characterized by young and/or slow slipping active faults.
    Description: Published
    Description: B11307
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: partially_open
    Keywords: active fault ; integrated geophysical investigations ; morpho-tectonic analysis ; paleoseismology ; Val d'Agri ; Southern Italy ; 1857 Earthquake ; 04. Solid Earth::04.02. Exploration geophysics::04.02.04. Magnetic and electrical methods ; 04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods ; 04. Solid Earth::04.02. Exploration geophysics::04.02.07. Instruments and techniques ; 04. Solid Earth::04.04. Geology::04.04.01. Earthquake geology and paleoseismology ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.04. Geology::04.04.11. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 102
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    New insights into banded tremor from the 2008–2009 Mount Etna eruption (2010)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We investigated the banded tremor activity occurring at Mt. Etna volcano between August-October 2008 during the 2008-2009 eruption. The banded tremor occurred in episodes lasting 25-30 minutes with intervals in between the episodes of about 25 minutes. Seismic signal analyses showed that the banded tremor was characterised by spectral contents, wavefields and source locations that differed from the “ordinary” volcanic tremor. The infrasound recordings exhibited an intermittent infrasonic tremor alternating with the banded tremor episodes. Finally, nonlinear analyses suggested that banded tremor system can be considered chaotic, implying: i) sensitive dependence on initial conditions, suggesting not only that a banded tremor system requires particular conditions to generate, but also that slight variations of these conditions are able to greatly change the features of the banded tremor or even to stop it; ii) long-term unpredictability, that is, the impossibility to forecast the long-term evolution of the banded tremor. On the basis of all these results and analogies with geyser models, we suggest a model of banded tremor that invokes alternating recharge-discharge phases. Banded tremor is due to “perturbations” in shallow aquifers, such as fluid movement and bubble growth or collapse due to hydrothermal boiling, triggered by the heat and hot fluid transfer from the underlying magma bodies. This heat-fluid transfer also causes an increasing pressure in the aquifer leading to fluid-discharge. During this process the seismic radiation decreases and, if the fluid-discharge is well coupled with the atmosphere, acoustic signals are generated.
    Description: Published
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Banded tremor ; Mt. Etna volcano ; volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 103
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    Active tectonics in Northern Victoria Land (Antarctica) inferred from the integration of GPS data and geologic setting. (2010)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Accepted for publication in Journal of Geophysical Research. Copyright (2010) American Geophysical Union.
    Description: A semi-permanent global positioning system (GPS) network of 30 vertices known as the Victoria Land Network for Deformation Control (VLNDEF) was set-up in the Austral summer of 1998 in Northern Victoria Land (NVL), including Terra Nova Bay (TNB), Antarctica. The locations were selected according to the known Cenozoic fault framework that is characterized by a system of NW-SE regional faults with right-lateral, strike-slip kinematics. The TNB1 permanent GPS station is within the VLNDEF, and following its installation on a bedrock monument in October 1998 it has been recording almost continuously. The GPS network has been surveyed routinely every two summers, using high-quality, dual-frequency GPS receivers. In this study, we present the results of a distributed session approach applied to the processing of the GPS data of the VLNDEF. An improved reference frame definition was implemented, including a new Euler pole, to compute the Antarctic intra-plate residual velocities. The projection of the residual velocities on the main faults in NVL show present-day activities for some faults, including the Tucker, Leap Year, Lanterman, Aviator, and David faults, with rightlateral strike-slip kinematics and local extensional/ compressional components. This active fault pattern divides NVL into eight rigid blocks, each characterized by their relative movements and rigid rotations. These show velocities of up to several mm/yr, which are comparable to those predicted by plate tectonic theory at active plate margins.
    Description: All researches were carried out in the framework of the Programma Nazionale di Ricerche in Antartide (PNRA) and financially supported by PNRA S.C.r.l.
    Description: Published
    Description: B12421
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: ANTARCTICA ; GEODESY ; MONITORING NETWORKS ; CRUSTAL DEFORMATION ; CONTINENTAL NEOTECTONICS ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 104
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    Water vapor sounding with the far infrared REFIR-PAD spectroradiometer from a high-altitude ground-based station during the ECOWAR campaign (2010)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The REFIR-PAD spectroradiometer was operated from the Testa Grigia Italian-Alps station in March 2007 during the Earth COoling by WAter vapouR emission (ECOWAR) measurement campaign, obtaining downwelling radiance spectra in the 100-1100 cm−1 range, under clear-sky condition and in the presence of cirrus clouds. The analysis of these mea surements has proven that the instrument is capable of determining precipitable water vapor with a total uncertainty of 5–7% by using the far-infrared rotational band of water. The measurement is unaffected by the presence of cirri, whose optical depth can be instead retrieved as an additional parameter. Information on the vertical profiles of water vapor volume mixing ratio and temperature can also be retrieved for three altitude levels. The ability to measure the water vapor column with a simple, uncooled instrument, capable of operating continuously and with a time resolution of about 10 minutes makes REFIR-PAD a very valuable instrument for meteorological and climatological studies for the characterization of the water vapor distribution.
    Description: In press
    Description: 1.7. Osservazioni di alta e media atmosfera
    Description: 1.10. TTC - Telerilevamento
    Description: JCR Journal
    Description: restricted
    Keywords: tropospheric water vapor ; IR spectroscopy ; REFIR-PAD ; ECOWAR ; 01. Atmosphere::01.01. Atmosphere::01.01.01. Composition and Structure ; 01. Atmosphere::01.01. Atmosphere::01.01.08. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 105
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    Bipolar climatology of GPS ionospheric scintillation at solar minimum (2011)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: High-rate sampling data of GNSS (Global Navigation Satellite Systems) ionospheric scintillation acquired by a network of GISTM (GPS Ionospheric Scintillation and TEC Monitor) receivers located in the Svalbard Islands, in Norway and in Antarctica have been analyzed. The aim is to describe the “scintillation climatology” of the high latitude ionosphere over both the poles under quiet conditions of the near-Earth environment. For climatology we mean to assess the general recurrent features of the ionospheric irregularities dynamics and temporal evolution on long data series, trying to catch eventual correspondences with scintillation occurrence. In spite of the fact that the sites are not geomagnetically conjugate, long series of data recorded by the same kind of receivers provide a rare opportunity to draw a picture of the ionospheric features characterizing the scintillation conditions over high latitudes. The method adopted is the Ground Based Scintillation Climatology, which produces maps of scintillation occurrence and of TEC relative variation to investigate ionospheric scintillations scenario in terms of geomagnetic and geographic coordinates, Interplanetary Magnetic Field conditions and seasonal variability. By means of such a novel and original description of the ionospheric irregularities, our work provides insights to speculate on the cause-effect mechanisms producing scintillations, suggesting the roles of the high latitude ionospheric trough, of the auroral boundaries and of the polar cap ionosphere in hosting those irregularities causing scintillations over both the hemispheres at high latitude. The method can constitute a first step towards the development of new algorithms to forecast the scintillations during space weather events.
    Description: Published
    Description: RS0D05
    Description: 1.7. Osservazioni di alta e media atmosfera
    Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale
    Description: JCR Journal
    Description: restricted
    Keywords: ionospheric scintillations ; climatology ; high latitude ionosphere ; space weather ; 01. Atmosphere::01.02. Ionosphere::01.02.04. Plasma Physics ; 01. Atmosphere::01.02. Ionosphere::01.02.07. Scintillations ; 05. General::05.01. Computational geophysics::05.01.03. Inverse methods
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  • 106
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    Forearc extension and slow rollback of the Calabrian Arc from GPS measurements (2011)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Here we describe the horizontal velocities of continuous GPS stations in the Calabrian Arc (CA) and surrounding regions. The appropriate reference frame to evaluate the crustal motion of the CA is considered by assessing the internal deformation and the relative motion of the crustal blocks in the foreland of the Apennines␣Ionian␣Maghrebides subduction system. We propose that the motion of CA rela- tive to the subducting Ionian lower plate is most properly assessed by minimizing the GPS velocities in Apulia. In this reference frame the significant ␣2 mm/yr southeast- ward motion of the stations on the Ionian flank of the CA shows that the arc is still moving towards the trench in agreement with the observations of active shortening in the Ioanian wedge. This southeastward migration is associated to 1.4 ± 0.3 mm/yr E␣W extension of the forearc in northern Calabria, comparable with the seismic strain averaged in the last 500 years. The limited subaerial exposure decreases the resolution on locking of the subduction interface but the distribution and direction of crustal extension along the CA impose important constraints on geodynamic interpreta- tions of the area.
    Description: Published
    Description: L17304
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: Calabrian Arc ; GPS ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 107
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    Evidence for surface faulting events along the Paganica fault prior to the 6 April 2009 L’Aquila earthquake (central Italy) (2011)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: main article
    Description: We performed paleoseismological investigations at four sites across the normal Paganica fault (PF) (source of the 2009 Mw 6.3 L’Aquila earthquake), with the goal of reconstructing the rupture history and of contributing to the evaluation of the maximum event expected along the PF. We recognized five distinct surface faulting earthquakes (including the 2009) in the trenches. The age of the penultimate event is consistent with the 1461 earthquake; the third event back occurred around 1000 AD. The two oldest events have larger uncertainties and occurred in the interval 760 BC–670 AD and 2900–760 BC, respectively. The along‐strike vertical displacement for each paleoevent has a limited variability consistently with the fairly homogeneous slip observed in 2009 along the northern part of the rupture. Conversely, the throws change between distinct events and range between 0.15 m in 2009 (maximum estimate) and close to 0.4 (lower bound estimate) in earlier events. These paleorecords and the high fault escarpments imply that earthquakes larger than 2009 occurred on the PF, with implications for the level of hazard. Recurrence intervals also reflect a change with time, the average interval before ∼1000 AD is longer compared to that after this date. Two events occurred in the 2000– 4000 years preceding ∼1000 AD, while three events occurred since ∼1000 AD. The age uncertainties affecting the interpreted events prevent the evaluation of a unique value for interevent interval; the older events appear closely spaced in time or far apart depending on the upper or lower boundary of the age interval. We tentatively assign an average interevent time of ∼500 years for the three youngest events, whereas the time elapsed between the previous ones could be larger, in the order of 1000–2000 years. We calculate a late Pleistocene dip‐slip rate for the PF of 0.2–0.4 mm/yr, consistent with 0.25–0.5 mm/yr for the early Pleistocene. Using age and throw of individual events, we calculate a similar late Holocene average dip‐slip rate of ∼0.3–0.4 mm/yr. This suggests that the portion of the PF where the 2009 continuous surface faulting occurred has fairly a constant average slip release since late Pleistocene. Finally, we discuss different rupture scenarios and alternative models of occurrence compatible with our data and their variability.
    Description: This work was partially funded by the Italian Dipartimento della Protezione Civile in the frame of the 2007–2009 Agreement with Istituto Nazionale di Geofisica e Vulcanologia (INGV).
    Description: Published
    Description: B07308
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: 2009 L'Aquila seismic sequence ; paleoearthquakes ; Paganica fault ; 04. Solid Earth::04.04. Geology::04.04.01. Earthquake geology and paleoseismology
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  • 108
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    Late Quaternary sediments from deep!sea sediment drifts on the Antarctic Peninsula Pacific margin: Climatic control on provenance of minerals (2011)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We present results of detailed paleomagnetic investigations on deep!sea cores from sediment drifts located along the Pacific continental margin of the Antarctic Peninsula. High!resolution magnetic measurements on u channel samples provide detailed age models for three cores collected from drift 7, which document an age of 122 ka for the oldest sediments recovered near the drift crest at site SED!07 and a high sedimentation rate (11 cm/kyr) at site SED!12 located close to the Alexander Channel system. Low! and high!temperature magnetic measurements in conjunction with microscopic and mineralogic observations from drifts 4, 5 and 7 indicate that pseudosingle!domain detrital titanomagnetite (partially oxidized and with limited Ti substitution) is the dominant magnetic mineral in the drift sediments. The titanomagnetite occurs in two magnetic forms: (1) a low!coercivity form similar to laboratory!synthesized titanomagnetite and (2) a high!coercivity form (Bcr 〉 60 mT). These two forms vary in amount and stratigraphic distribution across the drifts. We did not find evidence for diagenetic magnetic iron sulfides as has been previously suggested for these drift deposits. The observed change of magnetic mineralogy in sediments deposited during Heinrich events on drift 7 appears to be related to warming periods, which temporarily modified the normal glacial transport pathways of glaciogenic detritus to and along the continental rise and thus resulted in deposition of sediments with a different provenance. Understanding this sediment provenance delivery signature at a wider spatial scale should provide information about ice sheet dynamics in West Antarctica over the last !100 kyr.
    Description: Published
    Description: B06104
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: partially_open
    Keywords: Antarctic Peninsula ; Pacific margin ; sediment drift ; late Pleistocene ; Mineral magnetism ; relative palaeointensity ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.09. Environmental magnetism
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  • 109
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    Dynamics of a lava fountain revealed by geophysical, geochemical and thermal satellite measurements: The case of the 10 April 2011 Mt Etna eruption (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Geophysical (tilt, seismic tremor and gravity signals), geochemical (crater SO2 flux) and infrared satellite measurements are presented and discussed to track the temporal evolution of the lava fountain episode occurring at Mt Etna volcano on 10 April 2011. The multi-disciplinary approach provides insight into a gas-rich magma source trapped in a shallow storage zone inside the volcano edifice. This generated the fast ascending gas-magma dispersed flow feeding the lava fountain and causing the depressurization of a deeper magma storage. Satellite thermal data allowed estimation of the amount of erupted lava, which, summed to the tephra volume, yielded a total volume of erupted products of about 1 106 m3. Thanks to the daylight occurrence of this eruptive episode, the SO2 emission rate was also estimated, showing a degassing cycle reaching a peak of 15,000 Mg d 1 with a mean daily value of 5,700 Mg d 1. The SO2 data from the previous fountain episode on 17–18 February to 10 April 2011, yielded a cumulative degassed magma volume of about 10.5 106 m3, indicating a ratio of roughly 10:1 between degassed and erupted volumes. This volumetric balance, differently from those previously estimated during different styles of volcanic activities with long-term (years) recharging periods and middle-term (weeks to months) effusive eruptions, points toward the predominant role played by the gas phase in generating and driving this lava fountain episode.
    Description: Published
    Description: L24307
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: restricted
    Keywords: Mt. Etna ; lava fountain ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 110
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    Statistics between mainshocks and foreshocks in Italy and Southern California (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The most used and accepted models for daily forecasts are based on short‐term space and time earthquake clustering for occurrence rates and on the Gutenberg‐ Richter law for the frequency‐magnitude. These models have been demonstrated to produce reliable prospective space‐time‐magnitude forecasts during an aftershock sequence, but their skill in forecasting mainshocks is still under discussion. This paper studies the foreshock statistics of the Italian and Californian seismicity in two ways: i) we compare the foreshock activity observed in real seismic catalogs and in synthetic catalogs derived from a pure Epidemic‐Type Aftershock Sequence (ETAS) model; ii) we analyze the triggering capability of earthquakes using different ETAS parameterizations, in order to check whether large events are triggered in the same way as regular earthquakes. The results indicate that the foreshock activity observed in the real catalogs is compatible with what is expected by the ETAS model. Moreover, we find that the empirical foreshock rates have an intrinsic variability due to limited sampling that may explain most of the differences found so far in different seismic catalogs.
    Description: Published
    Description: L09310
    Description: 4.2. TTC - Modelli per la stima della pericolosità sismica a scala nazionale
    Description: JCR Journal
    Description: reserved
    Keywords: foreshocks ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability
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  • 111
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    Variations of crustal elastic properties during the 2009 L’Aquila earthquake inferred from cross correlations of ambient seismic noise (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We retrieve seismic velocity variations within the Earth’s crust in the region of L’Aquila (central Italy) by analyzing cross␣correlations of more than two years of continuous seis- mic records. The studied period includes the April 6, 2009, Mw 6.1 L’Aquila earthquake. We observe a decrease of seis- mic velocities as a result of the earthquake’s main shock. After performing the analysis in different frequency bands between 0.1 and 1 Hz, we conclude that the velocity varia- tions are strongest at relatively high frequencies (0.5–1 Hz) suggesting that they are mostly related to the damage in the shallow soft layers resulting from the co␣seismic shaking
    Description: Published
    Description: L24304
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: JCR Journal
    Description: reserved
    Keywords: seismic noise ; L'Aquila Earthquake ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
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  • 112
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    In-situ degassing study on crystal-bearing Stromboli basaltic magmas: Implications for Stromboli explosions (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Three-dimensional crystal and bubble sizes and distributions in experimentally produced vesicular crystal-bearing Stromboli basalts and natural scoria were studied with X-ray microtomography (μCT) at high (1.85 μm) and low (5.46–9.0 μm) resolution. The permeabilities from lattice Boltzmann (LB) simulations and experimental measurements are about 1–2 orders of magnitude higher than in aphyric Stromboli basalts at porosity 31.6–55.3%. We propose that the higher permeability in crystal-bearing samples results in highly efficient degassing in shallow, highly porphyritc (HP) magma as opposed to the deeper, aphyric (LP) magma. In paroxysmal explosions, the LP magma flows up in a cylindrical conduit due to the density and viscosity difference between the two magmas. This type of convection can cause the LP magma with exsolved gas to be efficiently transferred through the overlying HP magma, potentially resulting in the more-violent paroxysmal explosions.
    Description: Published
    Description: L17309
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: reserved
    Keywords: Experimental volcanism ; Stromboli ; degassing ; crystal-bearing magmas ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
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  • 113
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    Determining rheology from deformation data: The case of central Italy (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-03
    Description: The study of geodynamics relies on an understanding of the strength of the lithosphere. However, our knowledge of kilometer‐scale rheology has generally been obtained from centimeter‐sized laboratory samples or from microstructural studies of naturally deformed rocks. In this study, we present a method that allows rheological examination at a larger scale. Utilizing forward numerical modeling, we simulated lithospheric deformation as a function of heat flow and rheological parameters and computed several testable predictions including horizontal velocities, stress directions, and the tectonic regime. To select the best solutions, we compared the model predictions with experimental data. We applied this method in Italy and found that the rheology shows significant variations at small distances. The strength ranged from 0.6 ± 0.2 TN/m within the Apennines belt to 21 ± 6 TN/m in the external Adriatic thrust. These strength values correspond to an aseismic mantle in the upper plate and to a strong mantle within the Adriatic lithosphere. With respect to the internal thrust, we found that strike‐slip or transpressive, but not compressive, earthquakes can occur along the deeper portion of the thrust. The differences in the lithospheric strength are greater than our estimated uncertainties and occur across the Adriatic subduction margin. Using the proposed method, the lithospheric strength can be also determined when information at depth is scarce but sufficient surface data are available. Citation: Carafa, M. M. C., and S. Barba (2011), Determining rheology from deformation data: The case of central Italy, Tectonics, 30, TC2003, doi:10.1029/2010TC002680.
    Description: Published
    Description: TC2003
    Description: JCR Journal
    Description: restricted
    Keywords: Rheology ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous
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  • 114
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    Variability of foF2 over Rome and Gibilmanna during three solar cycles (1976-2000) (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-03
    Description: Hourly validated values of the F2-layer critical frequency (foF2) recorded at Rome, Italy (geographic coordinates 41.8ºN, 12.5ºE; geomagnetic coordinates 42.0ºN, 93.8ºE), and Gibilmanna, Italy (geographic coordinates 37.6ºN, 14.0ºE; geomagnetic coordinates 38.1ºN, 93.6ºE), along with the hourly quiet time reference values of foF2 (foF2QTRV) were considered around periods of minimum and maximum solar activity over the years 1976–2000. The foF2 data set was specifically organized in order to obtain an overall trend both for low and high solar activity, and different dispersion indices were used. The results obtained show that (1) at Rome, the foF2 variability is always greater during periods of high solar activity (HSA) in the hourly ranges 00:00–02:00 UT and 20:00–23:00 UT during winter months, and in the hourly ranges 00:00–10:00 UT and 04:00–16:00 UT during equinoctial and summer months respectively; (2) on the whole, around midday, for low solar activity (LSA), the foF2 variability is smaller at the equinoxes than at the solstices; for HSA, it is greater at equinoxes than at solstices; (3) for LSA, at Gibilmanna the foF2 variability is in general larger than at Rome, especially in summer, and it is characterized by a number of relative minimums and maximums greater than those observed at Rome; (4) at Rome, for both LSA and HSA, the passage of solar terminator at sunset significantly affects ionospheric variability in January, April, August, and November, at Gibilmanna in August, September, and November; (5) several variability peaks before sunrise and after sunset are observed in both stations; (6) on a monthly basis, for both LSA and HSA, a semiannual variation of foF2 variability is observed at both Rome and Gibilmanna; and (7) evidence of ionospheric variability at the typical heights of the F region, connected to upward propagating gravity waves triggered by solar terminator, is observed at Rome during some days characterized by HSA in the equinoctial months.
    Description: Published
    Description: A05316
    Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale
    Description: JCR Journal
    Description: reserved
    Keywords: F2 layer ; mid-latitude ionosphere ; ionospheric variability ; standard deviation ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous ; 01. Atmosphere::01.02. Ionosphere::01.02.02. Dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 115
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    Flank instability structure of Mt. Etna inferred by a magnetotelluric survey (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: This paper presents a magnetotelluric (MT) survey of the unstable eastern flank of Mt. Etna. We take thirty soundings along two profiles oriented in the N-S and NW-SE directions, and from these data recover two 2D resistivity models of the subsurface. Both models reveal three major layers in a resistive-conductive-resistive sequence, the deepest extending to 14 km bsl. The shallow layer corresponds to the volcanic cover, and the intermediate conductive layer corresponds to underlying sediments segmented by faults. These two electrical units are cut by E-W-striking faults. The third layer (basement) is interpreted as mainly pertinent to the Apennine-Maghrebian Chain associated with SW-NE-striking regional faults. The detailed shapes of the resistivity profiles clearly show that the NE Rift is shallow-rooted ( 0–1 km bsl), thus presumably fed by lateral dikes from the central volcano conduit. The NW-SE profile suggests by a series of listric faults reaching up to 3 km bsl, then becoming almost horizontal. Toward the SE, the resistive basement dramatically dips (from 3 km to 10 km bsl), in correspondence with the Timpe Fault System. Several high-conductivity zones close to the main faults suggest the presence of hydrothermal activity and fluid circulation that could enhance flank instability. Our results provide new findings about the geometry of the unstable Etna flank and its relation to faults and subsurface structures.
    Description: This paper presents a magnetotelluric (MT) survey of the unstable eastern flank of Mt. Etna. We take thirty soundings along two profiles oriented in the N-S and NW-SE directions, and from these data recover two 2D resistivity models of the subsurface. Both models reveal three major layers in a resistive-conductive-resistive sequence, the deepest extending to 14 km bsl. The shallow layer corresponds to the volcanic cover, and the intermediate conductive layer corresponds to underlying sediments segmented by faults. These two electrical units are cut by E-W-striking faults. The third layer (basement) is interpreted as mainly pertinent to the Apennine-Maghrebian Chain associated with SW-NE-striking regional faults. The detailed shapes of the resistivity profiles clearly show that the NE Rift is shallow-rooted ( 0–1 km bsl), thus presumably fed by lateral dikes from the central volcano conduit. The NW-SE profile suggests by a series of listric faults reaching up to 3 km bsl, then becoming almost horizontal. Toward the SE, the resistive basement dramatically dips (from 3 km to 10 km bsl), in correspondence with the Timpe Fault System. Several high-conductivity zones close to the main faults suggest the presence of hydrothermal activity and fluid circulation that could enhance flank instability. Our results provide new findings about the geometry of the unstable Etna flank and its relation to faults and subsurface structures.
    Description: Published
    Description: B03216
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.2. Tettonica attiva
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: JCR Journal
    Description: restricted
    Keywords: Etna ; magnetotelluric ; flank instability ; volcano ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous ; 04. Solid Earth::04.02. Exploration geophysics::04.02.04. Magnetic and electrical methods ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.05. Geomagnetism::04.05.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous
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  • 116
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    Focal parameters, depth estimation, and plane selection of the worldwide shallow seismicity with M s ! 7.0 for the period – 1900– 1976 (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: A worldwide seismic catalog of source parameters is an important tool in many geophysical studies. Such a kind of database is available only since 1977 with the CMT catalog. The main goal of this paper is to compile a similar catalog for the time period 1900–1976 estimating the focal parameters of shallow seismicity (depth 70 km) with Ms ! 7.0 (607 events). In particular, this new catalog (FM0076) contains strike, dip, rake, and depth estimations for 588 earthquakes in the period 1900–1976. At each estimate two reliability flags are assigned. The first is linked to the availability of data, and the second is given by comparing focal mechanism estimations and the tectonics of the epicentral area. The estimation procedure is based on the knowledge of the moment tensor of shallow earthquakes after 1977. From these data, the new concept of Weighted Cumulative Moment Tensor (WCMT), which represents such a kind of moment tensor for a mean earthquake in the epicentral area, leads to estimate the focal parameters. The estimation method is also tested by comparing out our data set for the period 1977–1989 with the CMT one (91 events). This comparison reveals a good agreement between the two methods and confirms the reliability of the catalog FM0076.
    Description: Published
    Description: Q05005
    Description: 5.2. TTC - Banche dati di sismologia strumentale
    Description: JCR Journal
    Description: reserved
    Keywords: CMT solutions ; seismic catalog ; worldwide seismicity ; 04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods
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  • 117
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    How do volcanic rift zones relate to flank instability? Evidence from collapsing rifts at Etna (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Volcanic rift zones, characterized by repeated dike emplacements, are expected to delimit the upper portion of unstable flanks at basaltic edifices. We use nearly two decades of InSAR observations excluding wintertime acquisitions, to analyze the relationships between rift zones, dike emplacement and flank instability at Etna. The results highlight a general eastward shift of the volcano summit, including the northeast and south rifts. This steadystate eastward movement (1-2 cm/yr) is interrupted or even reversed during transient dike injections. Detailed analysis of the northeast rift shows that only during phases of dike injection, as in 2002, does the rift transiently becomes the upper border of the unstable flank. The flank's steady-state eastward movement is inferred to result from the interplay between magmatic activity, asymmetric topographic unbuttressing, and east-dipping detachment geometry at its base. This study documents the first evidence of steady-state volcano rift instability interrupted by transient dike injection at basaltic edifices.
    Description: Partially funded by INGV and the Italian DPC (DPC-INGV project V4 “Flank”). ERS and ENVISAT SAR data were provided by ESA through the Cat-1 project no. 4532 and the GEO Supersite initiative. The DEM was obtained from the SRTM archive. ERS-1/2 orbits are courtesy of the TU-Delft, The Netherlands. SAR data processing has been done at IREACNR, partially carried out under contract “Volcanic Risk System (SRV)” funded by the Italian Space Agency (ASI).
    Description: Published
    Description: L20311
    Description: 1.3. TTC - Sorveglianza geodetica delle aree vulcaniche attive
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 1.10. TTC - Telerilevamento
    Description: 3.2. Tettonica attiva
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: 3.6. Fisica del vulcanismo
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: restricted
    Keywords: flank instability ; rift zones ; 04. Solid Earth::04.03. Geodesy::04.03.99. General or miscellaneous ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy ; 04. Solid Earth::04.03. Geodesy::04.03.09. Instruments and techniques ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.08. Risk::05.08.99. General or miscellaneous
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  • 118
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    Multiphase flow dynamics of pyroclastic density currents during the May 18, 1980 lateral blast of Mount St. Helens (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The dynamics of the May 18, 1980 lateral blast at Mount St. Helens, Washington (USA), were studied by means of a three-dimensional multiphase flow model. Numerical simulations describe the blast flow as a high-velocity pyroclastic density current generated by a rapid expansion (burst phase, lasting less than 20 s) of a pressurized polydisperse mixture of gas and particles and its subsequent gravitational collapse and propagation over a rugged topography. Model results show good agreement with the observed large-scale behavior of the blast and, in particular, reproduce reasonably well the front advancement velocity and the extent of the inundated area. Detailed analysis of modeled transient and local flow properties supports the view of a blast flow led by a high-speed front (with velocities between 100 and 170 m/s), with a turbulent head relatively depleted in fine particles, and a trailing, sedimenting body. In valleys and topographic lows, pyroclasts accumulate progressively at the base of the current body after the passage of the head, forming a dense basal flow depleted in fines (less than 5 wt.%) with total particle volume fraction exceeding 10−1 in most of the sampled locations. Blocking and diversion of this basal flow by topographic ridges provides the mechanism for progressive current unloading. On ridges, sedimentation occurs in the flow body just behind the current head, but the sedimenting, basal flow is progressively more dilute and enriched in fine particles (up to 40 wt.% in most of the sampled locations). In the regions of intense sedimentation, topographic blocking triggers the elutriation of fine particles through the rise of convective instabilities. Although the model formulation and the numerical vertical accuracy do not allow the direct simulation of the actual deposit compaction, present results provide a consistent, quantitative model able to interpret the observed stratigraphic sequence.
    Description: Published
    Description: B06208
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: restricted
    Keywords: Mount St. Helens ; blast, multiphase flow ; numerical simulations ; pyroclastic density currents ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous
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  • 119
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    Reply to comment by D. Carbone and D. Patanè on “Multi-disciplinary investigation on a lava fountain preceding a flank eruption: the 10 May 2008 Etna case” (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Bonaccorso et al. [2011a] investigated the source and magma dynamics of the 10 May 2008 lava fountain at the South-East Crater (SEC) of Mount Etna through a multidisciplinary approach that integrated a wide data set ranging from bulk rock compositions of the erupted products to seismic tremor and long-period events, tilt and gravity signals. Using a large dataset, the study provided a robust framework in which the mechanism of the 10 May 2008 lava fountain is explained as a violent release of bubble-rich magma layer previously trapped at the top of a shallow reservoir located between −0.5 and 1.5 km above sea level (asl). This result is in agreement with recent relevant literature [Allard et al., 2005; Vergniolle and Ripepe, 2008; Aiuppa et al., 2010; Andronico and Corsaro, 2011; Bonaccorso et al., 2011b; Calvari et al., 2011; Vergniolle and Gaudemer, 2012]. In the introduction of their comment Carbone and Patanè [submitted] affirm that in their opinion the interpretation that “the lava fountain was generated by the fragmentation of a foam layer trapped at the top of shallow reservoir” is not soundly based. This comment’s conclusion is puzzling because one of the comment’s authors (D. Patanè) is also a co-author on the paper by Aiuppa et al. [2010] where the same conclusion, now criticized, was well supported (see figure 5 and conclusions of that paper). In particular, in the conclusions Aiuppa et al. [2010] reported that “The paroxysmal SEC episodes mark the violent release of a bubble-rich magma layer, with bubbles having relatively shallow reservoir ...", that is, the same conclusion now criticized in the comment. After this, the comment raises issues concerning the analysis and interpretation of gravity and tilt data in the multidisciplinary approach presented by Bonaccorso et al. [2011a]. The comment by Carbone and Patanè is divided into 4 paragraphs, labelled “1. Introduction”, “2. Gravity changes”, “3. Tilt changes” and “4. Concluding remarks” with only paragraphs 2 and 3 containing specific comments. In this reply, we address these two paragraphs, and we shall show how the assumptions underlying the comment are merely speculative and why the results presented by Bonaccorso et al.[2011a] remain valid.
    Description: Published
    Description: Q11009
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: open
    Keywords: Etna volcano ; lava fountain ; explosion mechanism ; volcano multi-disciplinary monitoring ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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  • 120
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    Comparative analysis of spread-F signature and GPS scintillation occurrences at Tucumán, Argentina (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We analyze data recorded from October 2010 to September 2011, during the ascending phase of the 24th solar cycle, from an Advanced Ionospheric Sounder-Istituto Nazionale di Geofisica e Vulcanologia ionosonde and a GPS Ionospheric Scintillation and total electron content (TEC) monitor scintillation receiver, colocated at low latitude in the Southern American longitudinal sector (Tucumán, 26.9°S, 294.6°E, magnetic latitude 15.5°S, Argentina). The site offers the opportunity to perform spread-F and GPS scintillation statistics of occurrence under the southern crest of the equatorial ionospheric anomaly. Spread-F signatures, classified into four types (strong range spread-F (SSF), range spread-F, frequency spread-F (FSF), and mixed spread-F), the phase and amplitude scintillation index (σΦ and S4, respectively), the TEC, and the rate of TEC parameter, marker of the TEC gradients, that can cause scintillations, are considered. The seasonal behavior results as follows: the occurrence of all four types of spread-F is higher in summer and lower in winter, while the occurrence of scintillations peaks at equinoxes in the postsunset sector and shows a minimum in winter. The correspondence between SSF and scintillations seems to be systematic, and a possible correlation between S4 and FSF peaks is envisaged at the terminator. The investigation focused also on two particular periods, from 12 to 16 March 2011 and from 23 to 29 September 2011, both characterized by the simultaneous presence of SSF signatures and scintillation phenomena, allowing to discuss the role of traveling ionospheric disturbances as a strong candidate causing ionospheric irregularities.
    Description: Published
    Description: 4483–4502
    Description: 1.7. Osservazioni di alta e media atmosfera
    Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale
    Description: JCR Journal
    Description: restricted
    Keywords: equatorial ionosphere ; scintillation ; spread-F ; 01. Atmosphere::01.02. Ionosphere::01.02.05. Wave propagation ; 01. Atmosphere::01.02. Ionosphere::01.02.06. Instruments and techniques ; 01. Atmosphere::01.02. Ionosphere::01.02.07. Scintillations ; 05. General::05.07. Space and Planetary sciences::05.07.99. General or miscellaneous
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  • 121
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    Projections of global changes in precipitation extremes from CMIP5 models (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Precipitation extremes are expected to increase in a warming climate, thus it is essential to characterise their potential future changes. Here we evalu- ate eight high-resolution Global Climate Model simulations in the twenti- eth century and provide new evidence on projected global precipitation ex- tremes for the 21st century. A significant intensification of daily extremes for all seasons is projected for the mid and high latitudes of both hemispheres at the end of the present century. For the subtropics and tropics, the lack of reliable and consistent estimations found for both the historical and fu- ture simulations might be connected with model deficiencies in the repre- sentation of organised convective systems. Low inter-model variability and good agreement with high-resolution regional observations are found for the twentieth century winter over the Northern Hemisphere mid and high lat- itudes.
    Description: Published
    Description: 4887–4892
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: open
    Keywords: extreme events ; precipitation ; cmip5 ; 01. Atmosphere::01.01. Atmosphere::01.01.02. Climate
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 122
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    The effect of particle size on the rheology of liquid-solid mixtures with application to lava flows: Results from analogue experiments (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We investigate the effect of crystal size on the rheology of basaltic magmas by means of a rheometer and suspensions of silicon oil with natural magmatic crystals of variable size (from 63 to 0.5 mm) and volume fraction fi (from 0.03 to 0.6). At constant fi, finer suspensions display higher viscosities than coarser ones. Shear thinning (flow index n 〈 1) occurs at fi 〉 0.1–0.2 and is more pronounced (stronger departure from the Newtonian behavior) in finer suspensions. Maximum packing and average crystal size displays a nonlinear, positive correlation, while yield stress develops at fi 〉 0.2–0.3 irrespective of the crystal size. We incorporate our results into physical models for flow of lava and show that, with respect to lava flows containing coarser crystals, those with smaller crystals are expected to: 1) flow at lower velocity, 2) have a lower velocity gradient, and 3) be more prone to develop a region of plug flow. Our experimental results explain the observation that phenocryst-bearing and microlite-bearing lavas at Etna volcano (Italy) show smooth pahoehoe and rough aa’ surfaces, respectively.
    Description: FIRB-MIUR ‘‘Research and Development of New Technologies for Protection and Defense of Territory from Natural Risks’’
    Description: Published
    Description: 2661-2669
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: restricted
    Keywords: rheology ; magmatic suspensions ; analogue model ; lava flo ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas
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  • 123
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    Environmental magnetic record of paleoclimate, unroofing of the Transantarctic Mountains, and volcanism in late Eocene to early Miocene glaci-marine sediments from the Victoria Land Basin, Ross Sea, Antarctica (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We synthesize environmental magnetic results for sediments from the Victoria Land Basin (VLB), which span a total stratigraphic thickness of 2.6 km and a ~17 Myr age range. We assess how magnetic properties record paleoclimatic, tectonic, and provenance variations or mixtures of signals resulting from these processes. The magnetic properties are dominated by large-scale magnetite concentration variations. In the late Eocene and early Oligocene, magnetite concentration variations coincide with detrital smectite concentration and crystallinity variations, which reflect paleoclimatic control on magnetic properties through influence on weathering regime; high magnetite and smectite concentrations indicate warmer and wetter climates and vice versa. During the early Oligocene, accelerated uplift of the Transantarctic Mountains gave rise to magnetic signatures that reflect progressive erosion of the Precambrian-Mesozoic metamorphic, intrusive, and sedimentary stratigraphic cover succession associated with unroofing of the adjacent Transantarctic Mountains. From the early Oligocene to the early Miocene, a consistent fining upward of magnetite particles through the recovered composite record likely reflects increased physical weathering with glacial grinding contributing to progressively finer grained Ferrar Dolerite-sourced magnetite. After 24 Ma, the magnetic properties of VLB sediments are primarily controlled by the weathering and erosion of McMurdo Volcanic Group rocks; increased volcanic glass contents contribute to the fining upward of magnetite grain size. Overall, long-term magnetic property variations record the first-order geological processes that controlled sedimentation in the VLB, including paleoclimatic, tectonic, provenance, and volcanic influences.
    Description: Published
    Description: 1845–1861
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: environmental magnetism ; Antarctica ; paleoclimate ; volcanism ; Ross Sea ; Cenozoic ; 03. Hydrosphere::03.01. General::03.01.06. Paleoceanography and paleoclimatology ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy ; 04. Solid Earth::04.05. Geomagnetism::04.05.09. Environmental magnetism
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  • 124
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    New insights on volcanic and tectonic structures of the southern Tyrrhenian (Italy) from marine and land seismic data (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We present results from the first crustal seismic tomography for the southern Tyrrhenian area, which includes ocean bottom seismometer (OBS) data and a bathymetry correction. This area comprises Mt. Etna, the Aeolian Islands, and many volcanic seamounts, including the Marsili Seamount. The seismicity distribution in the area depends on the complex interaction between tectonics and volcanism. The 3-D velocity model presented in this study is obtained by the inversion of P wave arrival times from crustal earthquakes. We integrate travel time data recorded by an OBS network (Tyrrhenian Deep Sea Experiment), the SN-1 seafloor observatory, and the land network. Our model shows a high correlation between the P wave anomaly distribution and seismic and volcanic structures. Two main low-velocity anomalies underlie the central Aeolian Islands and Mt. Etna. The two volumes, which are related to the well-known active volcanism, are separated and located at different depths. This finding, in agreement with structural, petrography, and GPS data from literature, confirms the independence of the two systems. The strongest negative anomaly is found below Mt. Etna at the base of the crust, and we associate it with the deep feeding system of the volcano. We infer that most of the seismicity is generated in brittle rock volumes that are affected by the action of hot fluids under high pressure due to the active volcanism in the area. Lateral changes of velocity are related to a transition from the western to the central Aeolian Islands and to the passage from continental crust to the Tyrrhenian oceanic uppermost mantle.
    Description: Published
    Description: 3703–3719
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: open
    Keywords: ocean bottom seismometers ; southern Tyrrhenian Sea ; seismic tomography ; Aeolian Islands ; Etna ; oceanic continental crust ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
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  • 125
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    Enhanced crystal fabric analysis of a lava flow sample by neutron texture diffraction: A case study from the Castello d’Ischia dome (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The crystal fabric of a lava has been analyzed for the first time by neutron texture diffraction. In this study we quantitatively investigate the crystallographic preferred orientation of feldspars in the Castello d’Ischia (Ischia Island, Italy) trachytic exogenous dome. The crystallographic preferred orientation was measured with the monochromatic neutron texture diffractometer SV7 at the Forschungszentrum Jülich in Germany and a Rietveld refinement was applied to the sum diffraction pattern. The complementary thin section analysis showed that the three-dimensional crystal shape and the corresponding shape preferred orientation are in agreement with the quantitative orientation distributions of the neutron texture data. The (0k0) crystallographic planes of the feldspars are roughly parallel to the local flow bands, whereas the other corresponding pole figures show that a pivotal rotation of the anorthoclase and sanidine crystals was active during the emplacement of this lava dome. In combination with scanning electron microscopy investigations, electron probe microanalysis, XRF, and X-ray diffraction, the Rietveld refinement of the neutron diffraction data indicates a slow cooling dynamic on the order of several months during their crystallization under subaerial conditions. Results attained here demonstrate that neutron texture diffraction is a powerful tool that can be applied to lava flows.
    Description: Published
    Description: 179-196
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: restricted
    Keywords: neutron diffraction ; crystal fabric ; 04. Solid Earth::04.01. Earth Interior::04.01.04. Mineral physics and properties of rocks ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology ; 04. Solid Earth::04.04. Geology::04.04.07. Rock geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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  • 126
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    An analysis of tropical instability waves in a numerical model of the Pacific Ocean - 1. Spatial variability of the waves (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Unstable oscillations confined within the mixed layer close to the equator are generated in wind-forced experiments performed in a multilevel general circulation model configured for the tropical Pacific Ocean. The experiments indicate that the waves develop preferentially in the eastern Pacific along the northern temperature front. However, there is clear evidence of a second unstable region along the southern temperature front in the central Pacific. In both regions the instabilities propagate westward, but in the central Pacific their phase speed is considerably smaller. The differences between the wave characteristics in the eastern and central Pacific are closely correlated to the differences in the time mean conditions of the flow. The eastern instabilities have a structure with two peaks in amplitude: one located on the equator and the other a few degrees north of it. Their dispersion characteristics show many similarities to those of tropical instability waves (TIWs) observed in the Pacific Ocean, while the instabilities which grow in the central Pacific do not have any known observed correspondents. We explore the spatial variability of the simulated waves through a wavelet analysis, which provides detailed results on how the period and wavelength of the instabilities change as a function of longitude, latitude, and depth. The wavelet analysis reveals that in the eastern Pacific and close to the surface the TIWs have a phase speed of-48 cm/s, while in the central Pacific they have a phase speed of-11 cm/s. In particular, the change in the phase speed is due to a change in the dominant period of the TIWs: The period of the central Pacific instabilities is considerably longer than the period of the instabilities present in the eastern Pacific.
    Description: This work was supported by the Department of Commerce/NOAA grant NA56GP0026. One of the authors (SM) was partially supported by a NASA Global Change Fellowship NGT-30288.
    Description: Published
    Description: 29613-29635
    Description: 4A. Clima e Oceani
    Description: JCR Journal
    Description: restricted
    Keywords: Ocean modeling ; Equatorial Ocean ; Tropical Instability Waves ; 03. Hydrosphere::03.01. General::03.01.01. Analytical and numerical modeling
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    Intensity of the geomagnetic field in Europe for the last 3 ka: Influence of data quality on geomagnetic field modeling (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: One of the main challenges of paleomagnetic research is to obtain high-resolution geomagnetic field intensity reconstructions. For the last millennia, these reconstructions are mostly based on archeomagnetic data. However, the quality of the intensity data available in the databases is very variable, and the high scatter observed in the records clearly suggests that some of them might not be reliable. In this work we investigate how the geomagnetic field intensity reconstructions and, hence, our present knowledge of the geomagnetic field in the past, are affected by the quality of the data selected for modeling the Earth’s magnetic field. For this purpose we rank the European archeointensity data in four quality categories following widely accepted paleomagnetic criteria based on the methodology used during the laboratory treatment of the samples and on the number of specimens retained to calculate the mean intensities. Four geomagnetic field regional models have been implemented by applying the revised spherical cap harmonic analysis to these four groups of input data. Geomagnetic field models strongly depend on the used data set. The model built using all the available data (without any preselection) appears to be the less accurate, indicating some internal inconsistencies of the data set. In addition, some features of this model are clearly dominated by the less reliable archeointensity data, suggesting that such features might not reflect real variations of the past geomagnetic field. On the contrary, the regional model built on selected high-quality intensity data shows a very consistent intensity pattern at the European scale, confirming that the main intensity changes observed in Europe in the recent history of the geomagnetic field occurred at the continental scale.
    Description: Published
    Description: 2515–2530
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: open
    Keywords: Geomagnetism ; Paleomagnetism ; Archeomagnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals ; 04. Solid Earth::04.05. Geomagnetism::04.05.05. Main geomagnetic field ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism
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  • 128
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    Ultra-thick Triassic dolomites control the rupture behavior of the central Apennine seismicity: Evidence from magnetic modeling of the L’Aquila fault zone (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: High-resolution tomography from the 2009 L’Aquila extensional seismic sequence has shown that the Mw 6.1 main shock and most of the aftershocks occurred within a high velocity body (6.6≤Vp≤6.8 Km/s), located between depths of 3 and 12 km. The nature of the high Vp-body has remained speculative, although exhumed mafic deep crustal and upper mantle rocks (serpentinites) have been favoured. We used 3D magnetic anomaly modelling to investigate the plausibility of these favoured sources for the L’Aquila body. The modelling does not support the presence of high-velocity serpentinites with a 30-50% serpentinization degree and gabbros. Accordingly, we conclude that the high Vp-body may represent non-magnetic upper Triassic and possibly lower Liassic dolomites that have been drilled in neighbouring wells for 2-4 km. This conclusion is also consistent with the lack of a coherent gravity anomaly for the body. We speculate that ultra-thick Triassic dolomites reaching a thickness of 8 km may have been deposited in syntectonic wedges formed at the northern margin of the Ionian Sea, where oceanic spreading occurred in mid-late Triassic times.
    Description: Published
    Description: 6756–6770
    Description: 7A. Geofisica di esplorazione
    Description: JCR Journal
    Description: restricted
    Keywords: L’Aquila earthquake ; seismic tomography ; magnetic anomalies ; magnetic modelling ; dolomites; ; Apennines ; 04. Solid Earth::04.05. Geomagnetism::04.05.04. Magnetic anomalies
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  • 129
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    Geomagnetic jerks as chaotic fluctuations of the Earth’s magnetic field (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The geomagnetic field is chaotic and can be characterized by a mean exponential time scale〈t〉after which it is no longer predictable. It is also ergodic, so time analyses can substitute the more difficult phase space analyses. Taking advantage of these two properties of the Earth’s magnetic field, a scheme of processing global geomagnetic models in time is presented, to estimate fluctuations of the time scale t. Here considering that the capability to predict the geomagnetic field is reduced over periods of geomagnetic jerks, we propose a method to detect these events over a long time span. This approach considers that epochs characterized by relative minima of fluctuations in time scale t, i.e., those periods when a geomagnetic field is less predictable, are possible jerk occurrence dates. We analyze the last 400 years of the geomagnetic field (covered by the Gufm1 model) to detect minima of fluctuations, i.e., epochs characterized by low values of the time scale.Most of the well known jerks are confirmed through this method and a few others have been suggested. Finally, we also identify some short periods when the field is less chaotic (more predictable) than usual, naming these periods as steady state geomagnetic regime, to underline their opposite behavior with respect to jerks.
    Description: Published
    Description: 839–850
    Description: 3.4. Geomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: geomagnetic field ; geomagnetic jerks ; ergodicity ; chaos ; 04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals
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  • 130
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    The 4D imaging of the source of ground deformation at Campi Flegrei caldera (southern Italy) (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We have applied a tomographic imaging technique to the inversion of a DInSAR data set at Campi Flegrei caldera. This technique allowed us to determine the temporal and spatial distribution of volumetric strain sources up to 5 km depth. Results have shown complex spatial and temporal patterns, identifying important features that were not noticed before. The first result is the observation of positive strain sources (expansion) migrating upward (in 2000 and 2006). We have interpreted them as hot fluid batches injected at the bottom of the geothermal reservoir, migrating upward and reaching the surface. Furthermore we have identified an injection episode (in 1997), which was not recognized before. This batch did not reach the surface and probably dissipated by diffusion and lateral advection without producing significant ground uplift. The injection of fluid batches does not occur at the center of the caldera, but along its borders. The three identified injection episodes (in 1997, 2000 and 2006) occur in different points. In 2000 and 2006, the injected fluids migrated, subsequently, toward the center of the caldera. Our findings agrees with results of other geophysical and geochemical studies. These results suggest a new framework for the modeling of Campi Flegrei geothermal system and for the interpretation of data recorded by the multiparametric monitoring networks on the caldera.
    Description: Published
    Description: B08209
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: restricted
    Keywords: Campi Flegrei ; tomographic imaging ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 131
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    A scattering image of Campi Flegrei from the autocorrelation functions of velocity tomograms (2011)
    Wiley
    Details
    Publication Date: 2020-02-24
    Description: We propose a new quantitative approach for the joint interpretation of velocity and attenuation tomography images, performed through the lateral separation of scattering and intrinsic attenuation. The horizontal P-wave scattering attenuation structure below Campi Flegrei Caldera (CFC) is imaged using the autocorrelation functions (ACF) of P-wave vertical velocity fluctuations. Cluster analysis (CA) is then applied to interpret the images derived from ACF and the available P-wave total attenuation images at 2000m quantitatively. The analysis allows the separation of intrinsic and scattering attenuation on a 2-D plane, adding new geophysical constraints to the present knowledge about this volcanic area. The final result is a new, quantitative image of the past and present tectonic and volcanological state of CFC. P-wave intrinsic dissipation dominates in an area approximately located under the volcanic centre of Solfatara, as expected in a region with a large presence of fluids and gas. A north–south scattering attenuation region is mainly located below the zone of maximum uplift in the 1982–1984 bradiseismic crisis, in the sea side of the Pozzuoli bay, but also extending below Mt Nuovo. This evidence favours the interpretation in terms of a hard but fractured body, contoured by strong S-wave scatterers, corresponding to the Caldera rim: the region is possibly a section of the residual magma body, associated with the 1538 eruption of Mt Nuovo.
    Description: Published
    Description: 1304-1310
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Probability distributions ; Seismic attenuation ; Seismic tomography ; Statistical seismology ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
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  • 132
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    Integrated petrochemical and geophysical data reveals thermal distribution of the feeding conduits at Stromboli volcano, Italy (2012)
    American Geophysical Union
    Details
    Publication Date: 2020-02-24
    Description: Samples of scoriae erupted at Stromboli volcano during its persistent strombolian activity were collected between 2005 and 2008. Chemical and mineralogical compositions were obtained on products erupted from the three main crater sectors (SW, Central and NE). Small chemical variations indicate a different degree of evolution coupled with small difference of magma temperature 〈10°C. Analysis of the acoustic data for the same time period as the scoria sampling, indicates that puffing (a persistent overpressurized bubble degassing) was, on average, mainly observed at the central craters and at times moved to the NE sector. The cross-check of the two independent data sets allowed us to assess correlation between composition of products and puffing activity at vents. The hotter products are always erupted from the vents where puffing occurs indicating that slightly higher temperature can be the expression of an enhanced two-phase bubble flow dynamics.
    Description: Published
    Description: L08305
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: JCR Journal
    Description: reserved
    Keywords: Stromboli ; glass chemistry ; infrasound ; conduit dynamics ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas
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  • 133
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    Separating the thermal fingerprints of lava flows and simultaneous lava fountaining using ground-based thermal camera and SEVIRI measurements (2013)
    American Geophysical Union
    Details
    Publication Date: 2020-02-24
    Description: During effusive eruptions, thermal satellite monitoring has proved well suited to map the thermal flux from lava flows. However, during lava fountaining events, thermal contributions from active flows and from the fountain itself cannot be separated in low resolution satellite data. Here using photogrammetry and atmospheric modeling techniques, we compare radiance estimates from long-range ground-based thermal camera data (from which the fountain can be excluded) with those from SEVIRI satellite images for a fountaining event at Mount Etna (12 August 2011). The radiant heat flux determined from the ground-based camera showed similar behavior to values retrieved from Spinning Enhanced Visible and Infrared Imager (SEVIRI); thus the SEVIRI signal is interpreted to be dominated by the lava flows, with minimal contribution from the fountain. Furthermore, by modeling the cooling phase of each pixel inundated by lava, the mean thickness and lava volume (~2.4 × 106 m3) derived from camera images are comparable with those calculated from SEVIRI (~2.8 × 106 m3).
    Description: Published
    Description: 5058–5063
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: restricted
    Keywords: Etna ; satellite ; thermal monitoring ; SEVIRI ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 134
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    Real-time measurements of the concentration and isotope composition of atmospheric and volcanic CO2 at Mount Etna (Italy) (2014)
    American Geophysical Union
    Details
    Publication Date: 2020-02-24
    Description: We present unprecedented data of real-time measurements of the concentration and isotope composition of CO2 in air and in fumarole-plume gases collected in 2013 during two campaigns at Mount Etna volcano, which were made using a laser-based isotope ratio infrared spectrometer. We performed approximately 360 measurements/h, which allowed calculation of the δ13C values of volcanic CO2. The fumarole gases of Torre del Filosofo (2900mabove sea level) range from 3.24 ± 0.06‰to 3.71 ± 0.09‰, comparable to isotope ratio mass spectrometry (IRMS) measurements of discrete samples collected on the same dates. Plume gases sampled more than 1 km from the craters show a δ13C= 2.2 ± 0.4‰, in agreement with the crater fumarole gases analyzed by IRMS. Measurements performed along ~17km driving track from Catania to Mount Etna show more negative δ13C values when passing through populated centers due to anthropogenic-derived CO2 inputs (e.g., car exhaust). The reported results demonstrate that this technique may represent an important advancement for volcanic and environmental monitoring.
    Description: Published
    Description: 2382–2389
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Real-time data of CO2 content and δ13C in atmospheric/volcanic gases ; This study opens new perspective for the community for volcanic surveillance ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques ; 05. General::05.02. Data dissemination::05.02.01. Geochemical data
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  • 135
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    A new extended software package for quantitative paleoenvironmental reconstrutions (1999)
    American Geophysical Union
    In:  EPIC3EOS, Transactions of the American Geophysical Union, American Geophysical Union, 80(19), 223 p., pp. 223-223
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 136
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    Thirty years of satellite‐derived lava discharge rates at Etna: Implications for steady volumetric output (2011)
    American Geophysical Union
    Details
    Publication Date: 2020-02-24
    Description: We present a 30 year long data set of satellite‐derived time‐averaged lava discharge rates (TADR) for Mount Etna volcano (Sicily, Italy), spanning 1980–2010 and comprising 1792 measurements during 23 eruptions. We use this to classify eruptions on the basis of magnitude and intensity, as well as the shape of the TADR time series which characterizes each effusive event. We find that while 1983–1993 was characterized by less frequent but longer‐duration effusive eruptions at lower TADRs, 2000–2010 was characterized by more frequent eruptions of shorter duration and higher TADRs. However, roughly the same lava volume was erupted during both of these 11 year long periods, so that the volumetric output was linear over the entire 30 year period, increasing at a rate of 0.8 m3 s−1 between 1980 and 2010. The cumulative volume record can be extended back in time using data available in the literature. This allows us to assess Etna’s output history over 5 centuries and to place the current trend in historical context. We find that output has been stable at this rate since 1971. At this time, the output rate changed from a low discharge rate phase, which had characterized the period 1759 to 1970, to a high discharge rate phase. This new phase had the same output rate as the high discharge rate phase that characterized the period 1610–1669. The 1610–1669 phase ended with the most voluminous eruption of historic times.
    Description: This contribution is in support of the LMV‐based (PI: Franck Donnadieu) TerMex‐MYSTRALS project “Contribution à l’évaluation des risques associés aux activités éruptives majeures de l’Etna: approche multidisciplinaire des processus et précurseurs.”
    Description: Published
    Description: B08204
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: partially_open
    Keywords: Etna ; time averaged effusion rate ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas
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  • 137
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    Thermal insights into the dynamics of Nyiragongo lava lake from ground and satellite measurements (2013)
    American Geophysical Union
    Details
    Publication Date: 2020-02-24
    Description: We present new insights into the short- and long-term thermal activity of the Nyiragongo lava lake by ground-based and satellite infrared thermal imagery recorded in the first half of 2012. This is the very first time in which FLIR camera and SEVIRI data have been compared at this volcano. Maximum temperatures recorded at the molten lava were of ~1180 K, whereas the lake skin remained always below ~734 K in areas far from the upwelling zone and below ~843 K in those proximal to the source region. Ground-based imagery yielded mean radiative power values between ~0.80 and 1.10 GW. Consistently, satellite observations showed similar mean values of 1.10 GW. Overall the thermal activity of the lava lake was quite variable along the three days of field measurements at both daily and intradaily scale. SEVIRI radiative power values retrieved for the January–June 2012 period revealed fluctuations within the same variability range suggesting that no significant changes of the lava lake area had occurred over the six months. Comparison with previous radiative power estimates showed that our data well agree with the general increasing trend recorded since the reappearance of the lava lake after the last flank eruption in 2002.
    Description: This study was funded by Zanskar Producciones, Cabildo Insular de Tenerife, and the Instituto Volcanológico de Canarias. We are grateful to EUMETSAT for providing us SEVIRI data and to NASA for the Landsat 7 image. Letizia Spampinato thanks Dr S. Giammanco for funding her research activity on the VIGOR project.
    Description: Published
    Description: 5771–5784
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: restricted
    Keywords: thermal imagery ; satellite thermal images ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 138
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    Modeling of unrest signals in heterogeneous hydrothermal systems (2010)
    American Geophysical Union
    Details
    Publication Date: 2019-10-10
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: Monitoring of quiescent volcanoes, such as Campi Flegrei (Italy), involves the measurement of geochemical and geophysical parameters that are expected to change as eruptive conditions approach. Some of these changes are associated with the hydrothermal activity that is driven by the release of heat and magmatic fluids. This work focuses on the properties of the porous medium and on their effects on the signals generated by the circulating fluids. The TOUGH2 porous media flow model is applied to simulate a shallow hydrothermal system fed by a source of magmatic fluids. The simulated activity of the source, with periods of increased fluid discharge, generates changes in gas composition, gravity, and ground deformation. The same boundary conditions and source activity were applied to simulate the evolution of homogeneous and heterogeneous systems, characterized by different rock properties. Phase distribution, fluid composition, and the related signals depend on the nature and properties of the rock sequence through which the fluids propagate. Results show that the distribution of porosity and permeability affects all the observable parameters, controlling the timing and the amplitude of their changes through space and time. Preferential pathways for fluid ascent favor a faster evolution, with larger changes near permeable channels. Slower changes over wider areas characterize less permeable systems. These results imply that monitoring signals do not simply reflect the evolution of the magmatic system: intervening rocks leave a marked signature that should be taken into account when monitoring data are used to infer system conditions at depth.
    Description: This work was carried out within the research project V1-UNREST, founded by the Italian Civil Protection Department
    Description: Published
    Description: B09213
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: open
    Keywords: hydrothermal circulation ; observable ; volcanic unrest ; permeability ; 03. Hydrosphere::03.04. Chemical and biological::03.04.06. Hydrothermal systems ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 139
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    Shallow structure of Mt. Vesuvius volcano, Italy, from seismic array analysis (2011)
    American Geophysical Union
    Details
    Publication Date: 2017-05-23
    Description: SPAC method applied to data from a small aperture seismic array on Mt. Vesuvius gives the shallow velocity model.
    Description: Published
    Description: 481-484
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Array analysis ; shallow structure ; SPAC method ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
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  • 140
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    Source Mechanism of Long Period events recorded by a high density seismic network during the 2008 eruption on Mt Etna (2011)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: 129 Long Period (LP) events, divided in two families were recorded by 50 stations deployed on Mount Etna within an eruptive context in the second half of June 2008. In order to understand the mechanisms of these events, we perform moment tensor inversion. Numerical tests show that unconstrained inversion leads to reliable moment tensor solutions because of the close proximity of numerous stations to the source positions. However, single forces cannot be accurately determined as they are very sensitive to uncertainities in the velocity model. These tests emphasize the importance of using stations located as close as possible to the source in the inversion of LP events. Inversion of LP signals is initially unconstrained, in order to estimate the most likely mechanism. Constrained inversions then allow us to accurately determine the structural orientations of the mechanisms. Inversions for both families show mechanisms with strong volumetric components. These events are generated by cracks striking SW-NE for both families and dipping 70± SE (fam. 1) and 50± NW (fam. 2). The geometries of the cracks are different from the structures obtained by the location of these events. The orientation of the cracks is consistent with the local tectonic context on Mount Etna. The LP events seem to be a response to the lava fountain occuring on the 10th of May, 2008.
    Description: In press
    Description: (38)
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: open
    Keywords: Long-Period events ; earthquake source mechanism ; Etna Volcano ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 141
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    Kinematics and source zone properties of the 2004 Sumatra-Andaman earthquake and tsunami: Nonlinear joint inversion of tide gauge, satellite altimetry, and GPS data (2011)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We (re)analyzed the source of the 26 December 2004 Sumatra-Andaman earthquake and tsunami through a nonlinear joint inversion of an inhomogeneous data set made up of tide gauges, satellite altimetry, and far-field GPS recordings. The purpose is twofold: (1) the retrieval of the main kinematics rupture parameters (slip, rake, and rupture velocity) and (2) the inference of the rigidity of the source zone. We independently estimate the slip from tsunami data and the seismic moment from geodetic data to derive the rigidity. Our results confirm that the source of the 2004 Sumatra-Andaman earthquake has a complex geometry, constituted by three main slip patches, with slip peaking at ~30 m in the southern part of the source. The rake direction rotates counterclockwise at the northern part of the source, according to the direction of convergence along the trench. The rupture velocity is higher in the deeper than in the shallower part of the source, consistent with the expected increase of rigidity with depth. It is also lower in the northern part, consistent with known variations of the incoming plate properties and shear velocity. Our model features a rigidity (20–30 GPa) that is lower than the preliminary reference Earth model (PREM) average for the seismogenic volume. The source rigidity is one of the factors controlling the tsunami genesis: for a given seismic moment, the lower the rigidity, the higher the induced seafloor displacement. The general consistence between our source model and previous studies supports the effectiveness of our approach to the joint inversion of geodetic and tsunami data for the rigidity estimation.
    Description: Published
    Description: B02304
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Source process ; Sumatra ; Tsunami ; Joint Inversion ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
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  • 142
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    Radon and thoron emission from lithophysae-rich tuff under increasing deformation: An experimental study (2010)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: Radon and thoron emissions from lithophysae‐rich tuff under increasing deformation are measured to determine how mechanical damage affects gas emission levels in tuffs. Mechanical properties of rocks under stresses should be carefully considered to properly interpret data from geochemical field monitoring. Two samples are uniaxially loaded up to failure, while two others are unloaded at the end of the elastic phase, in order to achieve the highest compaction of existing pores. Changes in the porosity of deformed samples are evidenced by helium pycnometer and microscopy analyses. Radon and thoron exhalation rates are measured on groups of two samples by alpha spectrometer technique. Results show that tuff samples are characterised by a dual porosity consisting of a macroporosity, given by isolated large pores with sizes from mm‐ up to cm‐scale and a microporosity ranging between microns to hundreds of microns. At the end of the elastic phase pervasive pore collapse is observed, due to the closure of the cm‐scale macropores. This is mirrored by a significant decrease of radon and thoron release. After failure, a further reduction of porosity in the rock adjacent to the fault planes is observed due to extensive closure of both macropores and micropores. At this stage radon and thoron emissions increase. The formation of new exhaling surfaces is the main carrier of the bulk increase of radon and thoron exhalations, strongly prevailing over the densification carried out from the compaction mechanisms. In terms of volcanic hazard, negative anomalies in radon emissions should be considered as indicators of forthcoming ruptures. Key words: radon and thoron exhalation, tuff deformation, seismic precursor.
    Description: Published
    Description: L05305
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: reserved
    Keywords: Radon ; Rock deformation ; 04. Solid Earth::04.04. Geology::04.04.07. Rock geochemistry
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 143
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    Depth-dependent intrinsic and scattering seismic attenuation in north central Italy (2011)
    Wiley
    Details
    Publication Date: 2017-04-04
    Description: In this study the attenuation mechanism of seismic wave energy in north central Italy is estimated using low-magnitude earthquake local data recorded at six stations managed by INGV. Most of the analysed events are located along the Alpine chain in the zone of Iseo and Garda lakes, while a minor part in the Po valley. The zone investigated is characterized by the occurrence of significantly intense earthquakes (magnitude up to 6.6) the most recent occurred in 2004 close to the city of Sal`o on the coast of the Garda lake (Mw = 5.0). Due to the high population density and presence of industrial activity the investigated area is characterized by a high seismic risk. First, the ordinary Multiple Lapse Time Window Analysis (MLTWA) method is applied in the assumption of uniformvelocity and scattering and the couple of B0, the seismic albedo and Le−1, the extinction length inverse (corresponding to the total attenuation coefficient) is calculated in the frequency bands of 1.5, 3, 6 and 12 Hz. To retrieve more realistic estimates, the obtained values of B0 and Le−1 are corrected taking into account the effects of a depth-dependent earth model, consisting of an earth structure characterized by a transparent upper mantle and a heterogeneous crust. We find that the corrected intrinsic and scattering attenuation parameters (which are proportional to the inverse of the intrinsic/scattering quality factors, QI−1 and Qs−1) are strongly frequency dependent, with a prevalence of scattering attenuation over the intrinsic dissipation. The corrected and uncorrected values of total Q are in agreement with the total Q values obtained with different approaches for the same area.
    Description: Published
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Seismic Attenuation ; Coda Waves ; Wave Scattering and Diffraction ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
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  • 144
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    Reply to: Comment on ‘Insights from the Mw 6.3, 2009 L’Aquila earthquake (central Apennines) - Unveiling new seismogenic sources through their surface signatures: the adjacent San Pio Fault’ (2011)
    Wiley
    Details
    Publication Date: 2017-04-04
    Description: We reply to a comment by Messina et al., who strongly criticized our paper on the San Pio Fault, by showing that in areas of complex geology such as the central Apennines, where the current tectonic setting results from the superposition of different tectonic regimes, the equation: “most visible active fault = major seismogenic fault” can be misleading.
    Description: Published
    Description: 421-423
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: Seismotectonics ; morphotectonics ; active fault ; San Pio basin ; 04. Solid Earth::04.04. Geology::04.04.01. Earthquake geology and paleoseismology ; 04. Solid Earth::04.04. Geology::04.04.03. Geomorphology ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology
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  • 145
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    Seismoacoustic investigations of paroxysmal activity at Mt. Etna volcano: New insights into the 16 November 2006 eruption (2011)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: On 16 November 2006, a 1 day long paroxysmal eruption occurred at the summit craters of Mt. Etna volcano. A multiparametric approach, consisting of analyzing infrasonic, seismic, and video camera recordings, was carried out to follow its evolution. Volcanological and geophysical observations identified three eruptive phases. In the first phase, infrasonic and seismic characteristics reflected the highly explosive nature of the activity. Waveform characterization of infrasound events confirmed the activity of the several explosive vents at the summit of Southeast Crater (SEC). During the second phase, results highlighted the decoupling between seismic and infrasonic sources, which was due to the decrease in explosive activity and the reactivation of effusive vents located south of Bocca Nuova and on the saddle between Bocca Nuova and SEC. The third phase was the most intense and was characterized by various volcanic phenomena (pyroclastic flows, jets of dark ash, and white steam). The very high radiated infrasonic energy, together with infrasound event features, led us to infer a gas enrichment of the shallow magma column, preceding by a few minutes and likely related to the pyroclastic flows in the SEC area. After the eruption at SEC, variations in infrasound events related to the activity of Northeast Crater (NEC) were found. The observed spectral changes and the source mechanism modeling of the NEC infrasound events suggest the existence of a link in the plumbing system feeding the two craters.
    Description: Published
    Description: B09301
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Etna ; Infrasound ; volcanic tremor ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
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  • 146
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    FORMOSAT-3/COSMIC E region observations and daytime foE at middle latitudes (2011)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Ionosonde observations at Rome and Gibilmanna (Sicily) for some months of 2006–2007 were analyzed in the connection with recent COSMIC NmE results. Italy was completely located in the NmE enhanced zone according to COSMIC observations for the periods in question. COSMIC‐observed NmE values in the NmE enhanced zone do not coincide with NmE scaled from ionograms in accordance with the URSI Recommendations, but the IRI model correctly describes monthly median NmE contrary to the Chu et al. (2009) conclusion. Three month averaged COSMIC NmE values turn out to be close to monthly median NmE corresponding to the blanketing frequency fbEs. A conclusion is made that sporadic E practically permanently existing during daytime hours in summer strongly contributes to NmE observed by COSMIC. Possible reasons for the occurrence of the NmE enhanced zones at middle latitudes are discussed.
    Description: Published
    Description: A06307
    Description: 1.7. Osservazioni di alta e media atmosfera
    Description: JCR Journal
    Description: restricted
    Keywords: mid-latitude ionosphere ; sporadic E layer ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous ; 01. Atmosphere::01.02. Ionosphere::01.02.02. Dynamics
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  • 147
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    Source mechanism of long-period events recorded by a high-density seismic network during the 2008 eruption on Mount Etna (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: One hundred twenty-nine long-period (LP) events, divided into two families of similar events, were recorded by the 50 stations deployed on Mount Etna in the second half of June 2008. During this period lava was flowing from a lateral fracture after a summit Strombolian eruption. In order to understand the mechanisms of these events, we perform moment tensor inversions. Inversions are initially kept unconstrained to estimate the most likely mechanism. Numerical tests show that unconstrained inversion leads to reliable moment tensor solutions because of the close proximity of numerous stations to the source positions. However, single forces cannot be accurately determined as they are very sensitive to uncertainties in the velocity model. Constrained inversions for a crack, a pipe or an explosion then allow us to accurately determine the structural orientations of the source mechanisms. Both numerical tests and LP event inversions emphasise the importance of using stations located as close as possible to the source. Inversions for both families show mechanisms with a strong volumetric component. These events are most likely generated by cracks striking SW–NE for both families and dipping 70° SE (family 1) and 50° NW (family 2). For family 1 events, the crack geometry is nearly orthogonal to the dikelike structure along which events are located, while for family 2 the location gave two pipelike bodies that belong to the same plane as the crack mechanism. The orientations of the cracks are consistent with local tectonics, which shows a SW–NE weakness direction. The LP events appear to be a response to the lava fountain occurring on 10 May 2008 as opposed to the flank lava flow.
    Description: Published
    Description: B01304
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Etna Volcano ; long-period events ; source mechanism ; location ; plumbing systems ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 148
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    Narrow-band, transient signals in Central Apennines, Italy: hints for underground fluid migration? (2012)
    Wiley
    Details
    Publication Date: 2017-04-04
    Description: In this paper we investigate nature and properties of narrow-band, transient seismic signals observed by a temporary array deployed in the Val Tiberina area (central Apennines, Italy). These signals are characterized by spindle-shaped, harmonic waveforms with no clear S-wave arrivals. The first portion of the seismograms exhibits a main frequency peak centred at 4.5 Hz, while the spectrum of the slowly decaying coda is peaked at about 2 Hz. Events discrimination is performed using a matched-filtering technique, resulting in a set of 2466 detections spanning the 2010 January–March time interval. From a plane-wave-fitting procedure, we estimate the kinematic properties of signals pertaining to a cluster of similar events. The repetition of measurements over a large number of precisely aligned seismograms allows for obtaining a robust statistics of horizontal slownesses and propagation azimuths associated with the early portion of the waveforms. The P-wave arrival exhibits horizontal slownesses around 0.1 s km−1, thus suggesting waves impinging at the array almost vertically. Separately, we use traveltimes measured at a sparse network to derive independent constraints on epicentral location. Ray parameters and azimuths are calibrated using slowness measurements from a local, well-located earthquake. After this correction, the joint solution from traveltime inversion and array analysis indicates a source region spanning the 1–3 km depth interval. Considerations related to the source depth and energy, and the occurrence rate which is not related to the daily and weekly working cycles, play against a surface, artificial source. Instead, the close resemblance of these signals to those commonly observed in volcanic environments suggest a source mechanism related to the resonance of a fluid–filled fracture, likely associated with instabilities in the flux of pressurized CO2.
    Description: Published
    Description: 918-928
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: JCR Journal
    Description: reserved
    Keywords: Fracture and flow ; Earthquake source observations ; Interface waves ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
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  • 149
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    Vertical segregation in granular mass flows: A shear cell study (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-03
    Description: Non-fluidised, dry granular mass flows are obtained with rock fragments located on a rough rotating disk. In these flows that develop a quasi-rigid upper layer and a basal layer of colliding particles, dense clasts sink whereas light ones rise when surrounded by particles with intermediate density. Our experiments demonstrate that the presence of a quasi-rigid upper layer in granular mass flows does not prevent vertical segregation and that the formation of coarse-tail grading in pyroclastic flows does not require fluidising gases. High-speed videos reveal that vertical segregation in granular mass flow of rock fragments is generated by inertia differences between segregating clasts and matrix when they are both pushed upward by collisions with the basal layer. Coarse-tail grading occurs because the average segregation velocity of smaller clasts is smaller than that of larger clasts.
    Description: Published
    Description: L10402
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: pyroclastic flows ; vertical segregation ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism
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  • 150
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    Granular mass flows and Coulomb’s friction in shear cell experiments: Implications for geophysical flows (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-03
    Description: Granular mass flows of rock fragments are studied in the lab by means of a high-speed video camera at 2000 frames per second. These granular flows are generated using beds of pumice fragments positioned on a rough rotating disk, whose angular velocity is controlled by a motor. The experimental apparatus allows an understanding of the arrangement of the particles in granular mass flows with relatively small and relatively large values of the Savage number (the Savage number represents the ratio between grain collision stresses and gravitational grain contact stresses). In particular, these flows develop a basal layer of agitated and colliding particles underneath a relatively rigid upper layer. Our experimental results suggest the validity, on average, of the Coulomb’s relationship between shear and normal forces at the base of granular mass flows irrespective of their Savage number value. In Coulomb’s equation the shear stresses do not depend on the shear rate. We expect the Coulomb friction law to be valid also in moving pyroclastic flows. Our experiments suggest that the collisions and subsequent comminution of pumice fragments in moving pyroclastic flows could provide ash for the overriding ash clouds. In our experiments the amount of ash generated by particle-particle and particle-boundary interactions increases as the value of the Savage number increases. In nature, part of this ash may also simply move toward the base of the flows because of kinetic sieving.
    Description: Published
    Description: F04005
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: pyroclastic flows ; basal friction ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism
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  • 151
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    Space-time distribution of afterslip following the 2009 L’Aquila earthquake (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The inversion of multitemporal DInSAR and GPS measurements unravels the coseismic and postseismic (afterslip) slip distributions associated with the 2009 MW 6.3 L’Aquila earthquake and provides insights into the rheological properties and long-term behavior of the responsible structure, the Paganica fault. Well-resolved patches of high postseismic slip (10–20 cm) appear to surround the main coseismic patch (maximum slip ≈1 m) through the entire seismogenic layer above the hypocenter without any obvious depth-dependent control. Time series of postseismic displacement are well reproduced by an exponential function with best-fit decay constants in the range of 20–40 days. A sudden discontinuity in the evolution of released postseismic moment at ≈130 days after the main shock does not correlate with independent seismological and geodetic data and is attributed to residual noise in the InSAR time series. The data are unable to resolve migration of afterslip along the fault probably because of the time interval (six days) between the main shock and the first radar acquisition. Surface fractures observed along the Paganica fault follow the steepest gradients of postseismic line-of-sight satellite displacements and are consistent with a sudden and delayed failure of the shallow layer in response to upward tapering of slip. The occurrence of afterslip at various levels through the entire seismogenic layer argues against exclusive depth-dependent variations of frictional properties on the fault, supporting the hypothesis of significant horizontal frictional heterogeneities and/or geometrical complexities. We support the hypothesis that such heterogeneities and complexities may be at the origin of the long-term variable behavior suggested by the paleoseismological studies. Rupture of fault patches with dimensions similar to that activated in 2009 appears to have a ≈500 year recurrence time interval documented by paleoseismic and historical studies. In addition to that, paleoseismological evidence of large (〉0.5 m) coseismic offsets seems to require seismic events, recurring every 1000–2000 years, characterized by (1) multisegment linkage, (2) surface ruptures larger than in 2009, and (3) complete failure of the 2009 coseismic and postseismic patches.
    Description: Published
    Description: B02402
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Afterslip ; L'Aquila ; Apennines ; postseismic ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations
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  • 152
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    Estimating the vertical electron density profile from an ionogram: on the passage from true to virtual heights via the target function method (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-03
    Description: The paper describes a new simple method of calculation by which an artificial ionogram trace is obtained from a given vertical electron density profile. The method is discussed in terms of the target function method used by Autoscala to output a reliable estimation of the real vertical electron density profile associated to the recorded ionogram. This new approach solves the issue of the pole in the calculation of virtual height, and consequently eliminates all the divergence phenomena that sometimes characterized the artificial ionogram traces computed by Autoscala. In contrast to the POLAN procedure, the technique introduced in this paper to pass from true to virtual heights is not based on any arithmetical operation related to changes of integration variables. Since the target function method on which Autoscala is based requires that the passage from a vertical electron density profile to an artificial ionogram be repeated a very large number of times, this new calculation procedure is advantageous in terms of speeding up the associated processing time.
    Description: Published
    Description: RS1007
    Description: 1.7. Osservazioni di alta e media atmosfera
    Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale
    Description: JCR Journal
    Description: restricted
    Keywords: ionogram trace ; true height analysis ; vertical electron dendity profile ; virtual height ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous ; 01. Atmosphere::01.02. Ionosphere::01.02.05. Wave propagation ; 01. Atmosphere::01.02. Ionosphere::01.02.06. Instruments and techniques
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  • 153
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    Tropical Cyclone Effects on Arctic Sea Ice Variability (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: In recent years increasing interest has been put on the role that intense Tropical Cyclones can play in the climate system. The following study is aimed at highlighting the effects of strong Tropical Cyclones over the Tropical Atlantic on the mean climate. Their composite effect on the surface winds is made apparent by a wide cyclonic perturbation that affects a large portion of the Atlantic tropical Ocean. Teleconnection patterns, which are visible in the Sea Level Pressure anomalies associated with this Tropical Composite Cyclone, appear to link the activity of the hurricanes to the Arctic Ocean. A significant negative correlation between the energy dissipated by hurricanes in the Tropical atmosphere and the sea ice cover along the Transpolar Drift Stream path, has also been found.
    Description: Published
    Description: L17704
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: restricted
    Keywords: tropical cyclones ; arctic sea ice ; 01. Atmosphere::01.01. Atmosphere::01.01.02. Climate
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  • 154
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    Upper mantle structure below the European continent: Constraints from surface-wave tomography and GRACE satellite gravity data (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We here exploit fundamental mode Rayleigh and Love seismic wave information and the high resolution satellite global gravity model GGM02C to obtain a 1° × 1° 3-D image of: (a) upper-mantle isotropic shear-wave speeds; (b) densities; and (c) density-vS coupling below the European plate (20°N–90°N) (40°W–70°E). The 3-D image of the density-vS coupling provides unprecedented detail of information on the compositional and thermal contributions to density structures. The accurate and high-resolution crustal model allows us to compute a reliable residual topography to understand the dynamic implications of our models. The correlation between residual topography and mantle residual gravity anomalies defines three large-scale regions where upper mantle dynamics produce surface expression: the East European Craton; the eastern side of the Arabian Plate; and the Mediterranean Basin. The effects of mantle convection are also clearly visible at: (1) the Eastern Sirt Embayment; (2) the West African Craton northern margins; (3) the volcanically active region of the Canarian Archipelago; (4) the northern edge of the Central European Volcanic Province; and (5) the Northeastern part of the Atlantic Ocean, between Greenland and Iceland. Strong connections are observed among areas of weak radial anisotropy and areas where the mantle dynamics show surface expression. Although both thermal and additional dependencies have been incorporated into the density model, convective down-welling in the mantle below the East European Craton is required to explain the strong correlation between the estimated negative mantle residual anomalies and the negative residual topography.
    Description: DATEC MERG-CT-2007-046522 and NERIES INFRAST-2.1-026130
    Description: Published
    Description: B09401
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Europe ; GRACE ; density-velocity scaling relationship ; dynamic topography ; surface waves ; upper mantle density ; 04. Solid Earth::04.01. Earth Interior::04.01.01. Composition and state ; 04. Solid Earth::04.03. Geodesy::04.03.03. Gravity and isostasy ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 05. General::05.01. Computational geophysics::05.01.03. Inverse methods
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  • 155
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    Inconsistent magnetic polarities in magnetite-and greigite-bearing sediments: Understanding complex magnetizations in the late Messinian in the Adana Basin (southern Turkey) (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We present paleomagnetic, rock magnetic and scanning electron microscope data from three upper Messinian stratigraphic sections from the Adana Basin (southern Turkey). The collected samples are from fine-grained units, which were deposited during the Messinian Salinity Crisis (within subchron C3r). Paleomagnetic results reveal an inconsistent polarity record, related to a mixture of magnetite and greigite that hinders determination of a reliable magnetostratigraphy. Three classes of samples are recognized on the basis of paleomagnetic results. The first is characterized by a single magnetization component, with normal polarity, that is stable up to 530–580 C and is carried by magnetite. The second is characterized by a single magnetization component, with reversed polarity, that is stable up to 330–420 C. This magnetization is due to greigite, which developed after formation of slumps and before tectonic tilting of the studied successions. The third is characterized by reversed polarity, which is stable up to 530–580 C. We interpret this component as a primary magnetization carried by fine-grained and magnetically stable detrital magnetite. Results indicate that in the Adana Basin the assumption that a primary magnetization is carried by magnetite, and a magnetic overprint carried by greigite, does not hold because a late magnetic overprint has also been found for magnetite-bearing samples. Our data illustrate the complexity of magnetostratigraphic reconstructions in successions characterized by variable mixtures of magnetic minerals with different magnetic stability that formed at different stages. We demonstrate the need to perform detailed magnetic mineralogy analyses when conducting magnetostratigraphic studies of clay-rich sediments from marine or lacustrine environments.
    Description: Published
    Description: Q10002
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: Messinian ; remagnetization ; reversals ; rock and mineral magnetism ; southern Turkey ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.07. Rock magnetism
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  • 156
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    Comment on "Multidisciplinary investigation on a lava fountain preceding a flank eruption: The 10 May 2008 Etna case" by A. Bonaccorso et al. (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The paper "Multidisciplinary investigation on a lava fountain preceding a flank eruption: The 10 May 2008 Etna case", by Bonaccorso et al. (2011), presents a multi-parameter dataset encompassing the eruptive episode featured in the title. Through the dataset at their disposal, the authors tried to set constraints on the coupled phenomena which governed the paroxysmal event and subsequent flank eruption. Even though the joint analysis of different data offers considerable potential to extract additional information on the dynamics behind the observed phenomena, the most obvious implication is the risk of not treating all the available information with due care, which may lead to misinterpretation of the data. In the following, we discuss issues concerning the analysis and interpretation of gravity and tilt data in Bonaccorso et al. (2011) and show why, in our opinion, the conclusion that "all the data concur in indicating that the 10 May lava fountain was generated by the fragmentation of a foam layer trapped at the top of a shallow reservoir" is not soundly based.
    Description: Published
    Description: Q11008
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: embargoed_20130601
    Keywords: Volcanic eruptions ; Etna volcano ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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  • 157
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    An analytical model for gas overpressure in slug-driven explosions: Insights into Strombolian volcanic eruptions (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Strombolian eruptions, common at basaltic volcanoes, are mildly explosive events that are driven by a large bubble of magmatic gas (a slug) rising up the conduit and bursting at the surface. Gas overpressure within the bursting slug governs explosion dynamics and vigor and is the main factor controlling associated acoustic and seismic signals. We present a theoretical investigation of slug overpressure based on magma-static and geometric considerations and develop a set of equations that can be used to calculate the overpressure in a slug when it bursts, slug length at burst, and the depth at which the burst process begins. We find that burst overpressure is controlled by two dimensionless parameters: V′, which represents the amount of gas in the slug, and A′, which represents the thickness of the film of magma that falls around the rising slug. Burst overpressure increases nonlinearly as V′ and A′ increase. We consider two eruptive scenarios: (1) the “standard model,” in which magma remains confined to the vent during slug expansion, and (2) the “overflow model,” in which slug expansion is associated with lava effusion, as occasionally observed in the field. We find that slug overpressure is higher for the overflow model by a factor of 1.2–2.4. Applying our model to typical Strombolian eruptions at Stromboli, we find that the transition from passive degassing to explosive bursting occurs for slugs with volume 〉24–230 m3, depending on magma viscosity and conduit diameter, and that at burst, a typical Strombolian slug (with a volume of 100–1000 m3) has an internal gas pressure of 1–5 bars and a length of 13–120 m. We compare model predictions with field data from Stromboli for low-energy “puffers,” mildly explosive Strombolian eruptions, and the violently explosive 5 April 2003 paroxysm. We find that model predictions are consistent with field observations across this broad spectrum of eruptive styles, suggesting a common slug-driven mechanism; we propose that paroxysms are driven by unusually large slugs (large V′).
    Description: Published
    Description: B02206
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: restricted
    Keywords: Stromboli ; Taylor bubble ; basaltic volcanoes ; falling film ; gas slug ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 158
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    Complexity of theMw6.3 2009 L’Aquila (central Italy) earthquake: 2. Broadband strong motion modeling (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Near-fault strong-ground motions (0.1–10 Hz) recorded during the Mw 6.3 2009 L’Aquila earthquake exhibit great spatial variability. Modeling the observed seismograms allows linking distinct features of the observed wavefield to particular source and propagation effects and provides insights on strong motion complexity from this moderate magnitude event. We utilize a hybrid integral-composite approach based on a k-square kinematic rupture model, combining low-frequency coherent and high-frequency incoherent source radiation and providing omega-squared source spectral decay. Several source model features, proven to be stable by means of an uncertainty analysis in the preceding low-frequency (〈0.2 Hz) multiple finite-extent source inversion (Paper 1), were constrained. Synthetic Green’s functions are calculated in a 1D-layered crustal model including 1D soil profiles to account for site-specific response (where available). The results show that although the local site effects improve the modeling, the spatial broadband ground-motion variability is to large extent controlled by the rupture kinematics. The modeling thus confirms and further constraints the source model features, including the position and slip amount of the two main asperities, the largest asperity time delay and the rupture velocity distribution on the fault. Furthermore, we demonstrate that the crossover frequency dividing the coherent and incoherent wavefield, often considered independent on the station position, has to be variable in order to adequately reproduce both near and far station recordings. This suggests that the incoherency of the radiated wavefield is controlled by the wave-propagation phenomena and/or the initial updip rupture propagation was very smooth (coherent) up to relatively high frequencies (〉2 Hz)
    Description: Published
    Description: B0438
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: restricted
    Keywords: broad band modeling, source complexity, aquila earthquake ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
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  • 159
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    Ground deformations and volcanic processes as imaged by CGPS data at Mt. Etna (Italy) between 2003 and 2008 (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We analyze the kinematic and crustal deformations of Mt. Etna from 2003 to 2008 as imaged by the Mt. Etna continuous GPS (CGPS) network (Etna@net). Through a careful analysis of GPS time series, six coherent phases of crustal deformations have been identified, three inflation phases and three deflation phases, superimposed on a major inflation of the volcanic edifice since 2001. The inversions of GPS velocities have enabled: 1) a better understanding of the evolution of the volcanic sources acting beneath the volcano; 2) analysis of the strain rate patterns; and 3) a delineation of potential coupling between volcanic sources and the observed ground deformations. The modelling of the pressure sources has shown a separation between inflation and deflation sources. The deflation sources show an upward migration, from 5.5 toward 2.0 km (b.s.l.), while the inflation sources are located within 5.5 and 4.0 km (b.s.l.). Our results indicate that the kinematic and ground deformations of the mid-upper eastern flank are driven by the interplay between the effect of the magmatic sources and a south-eastward motion. Furthermore, clockwise rotations have been detected that prevailed over the eastern motion of the flank during the inflation phase preceding the 2004-2005 and 2006 eruptions. Finally, the accordance between the higher geodetic shear strain rates and the area with the highest seismic energy release shows that measured geodetic shear strain rates can provide useful information on the potential occurrence of seismic activity.
    Description: Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia,Catania, Italy. Department of Geosciences, State University of New York at Stony Brook, Stony Brook, New York, USA.
    Description: Published
    Description: B07208
    Description: 1.3. TTC - Sorveglianza geodetica delle aree vulcaniche attive
    Description: JCR Journal
    Description: restricted
    Keywords: Mt. Etna ground deformations ; Volcano monitoring ; Strain rate analysis ; Volcanic source modelling ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 160
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    The Ionian Sea:The oldest in situ ocean fragment of the world (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: It is well known that the Ionian Sea is characterized by thin (8-11 km) crystalline crust, thick (5-7 km) sedimentary cover, and low heat flow, typical for a Mesozoic (at least) basin. Yet seismic data have not yielded univocal interpretations, and a debate has developed on the oceanic vs. “thinned continental” nature of the Ionian basin. Here we analyze the magnetic anomaly pattern of the Ionian Sea, and compare it to synthetic fields produced by a geopotential field generator, considering realistic crust geometry. The Ionian basin is mostly characterized by slightly negative magnetic residuals, and by a prominent positive (150 nT at sea level) “B” anomaly at the northwestern basin margin. We first test continental crust models, considering a homogeneous crystalline crust with K=1x10-3, then a 5 km thick deep crustal layer of serpentinite (K=1x10-1). First model yields insignificant anomalies, while the second gives an anomaly pattern anti-correlated with the observed residuals. We subsequently test oceanic crust models, considering a 2 km thick 2A basaltic layer with K=5x10-3, magnetic remanence of 5 A/m, and a unique magnetic polarity (no typical oceanic magnetic anomaly stripes are apparent in the observed data set). Magnetic remanence directions were derived from Pangean-African paleopoles in the 290-190 Ma age window. Only reverse-polarity models reproduce the B anomaly, and among them the 220-230 Ma models best approximate magnetic features observed on the abyssal plain and at the western basin boundary. The Ionian Sea turns out to be the oldest preserved oceanic floor known so far.
    Description: Published
    Description: B12101
    Description: 3.4. Geomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: ionian sea ; neo-Tethys ; magnetic anomalies ; magnetic modelling ; oceanic crust ; 04. Solid Earth::04.05. Geomagnetism::04.05.04. Magnetic anomalies
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 161
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    Earthquake sound perception (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Sound is an effect produced by almost all earthquakes. Using a web-based questionnaire on earthquake effects that included questions relating to seismic sound, we collected 77,000 responses for recent shallow Italian earthquakes. An analysis of audibility attenuation indicated that the decrease of the percentage of respondents hearing the sound was proportional to the logarithm of the epicentral distance and linearly dependent on earthquake magnitude, in accordance with the behavior of ground displacement. Even if this result was based on Italian data, qualitative agreement with the results of theoretical displacement, and of a similar study based on French seismicity suggests wider validity. We also found that, given earthquake magnitude, audibility increased together with the observed macroseismic intensity, leading to the possibility of accounting for sound audibility in intensity assessment. Magnitude influenced this behavior, making small events easier to recognize, as suggested by their frequency content.
    Description: Published
    Description: L24301
    Description: 1.11. TTC - Osservazioni e monitoraggio macrosismico del territorio nazionale
    Description: JCR Journal
    Description: open
    Keywords: earthquake sound ; questionnaires ; macroseismic intensity ; ground displacement ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
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  • 162
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    The failed eruption of Mt. Etna in December 2005: evidence from volcanic tremor analyses (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Strong changes in seismic radiation, comparable to those preceding and/or accompanying eruptive activity in recent years, were recorded at Mt. Etna volcano, Italy, from November 2005 to January 2006. The amplitude of volcanic tremor peaked in mid-December 2005 after a continuous, slow increase from August 2005 onwards, during which neither effusive nor paroxysmal activity was observed by volcanologists and alpine guides. During this time span, the centroid locations of volcanic tremor moved towards the surface, more and more clustered below the summit craters. The application of pattern classification analysis based on Self-Organizing Maps and fuzzy clustering to volcanic tremor data highlighted variations in the frequency domain as well. These changes were temporally associated with ground deformation variations, as indicative of a mild inflation of the summit of the volcano, and with a conspicuous increase in the SO2 plume-flux emission. Overall, we interpret this evidence as the result of recharging of the volcanic feeder at depth (〉 3 km below sea level) during which magma did not reach the shallow plumbing system.
    Description: Published
    Description: 4989–5005
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: embargoed_20140606
    Keywords: time series analysis ; volcano seismology ; volcano monitoring ; neural network and fuzzy logic ; seismic tomography ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
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  • 163
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    Probabilistic modeling of future volcanic eruptions at Mount Etna (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The statistical analysis of volcanic activity at Mt Etna was conducted with the twofold aim of (1) constructing a probability map for vent opening of future flank eruptions and (2) forecasting the expected number of eruptive events at the summit craters. The spatiotemporal map of new vent opening at Etna volcano is based on the analysis of spatial locations and frequency of flank eruptions starting from 1610. Thanks to the completeness and accuracy of historical data over the last four centuries, we examined in detail the spatial and temporal distribution of flank eruptions showing that effusive events follow a nonhomogenous Poisson process with space-time varying intensities. After demonstrating the spatial nonhomogeneity and the temporal nonstationarity of flank eruptions at Etna, we calculated the recurrence rates (events expected per unit area per unit time) and produced different spatiotemporal probability maps of new vent opening in the next 1, 10 and 50 years. These probabilistic maps have an immediate use in evaluating the future timing and areas of Etna prone to volcanic hazards. Finally, the results of the analysis of the persistent summit activity during the last 110 years indicate that the hazard rate for eruptive events is not constant with time, differs for each summit crater of Mt Etna, highlighting a general increase in the eruptive frequency starting from the middle of last century and particularly from 1971, when the SE crater was formed.
    Description: This work was developed in the frame of the TecnoLab, the Laboratory for the Technological Advance in Volcano Geophysics organized by INGV-CT, DIEES-UNICT, and DMI-UNICT.
    Description: Published
    Description: 1925-1935
    Description: 1V. Storia e struttura dei sistemi vulcanici
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: 3V. Dinamiche e scenari eruttivi
    Description: 4V. Vulcani e ambiente
    Description: 3IT. Calcolo scientifico e sistemi informatici
    Description: JCR Journal
    Description: restricted
    Keywords: Etna ; probabilistic modeling ; eruption ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 05. General::05.01. Computational geophysics::05.01.02. Cellular automata, fuzzy logic, genetic alghoritms, neural networks ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis ; 05. General::05.01. Computational geophysics::05.01.05. Algorithms and implementation ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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  • 164
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    Ocean, sea-ice, atmosphere oscillations in the Southern Ocean as simulated by the SINTEX coupled model (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: 1This study evaluates the Antarctic Circumpolar Wave (ACW) as simulated by the SINTEX coupled model. We found evidence that sea-ice treatment plays a crucial role on simulating the ACW. In particular, SST anomalies at interannual time scales describe a propagating ACW-like pattern when a dynamic thermodynamic sea-ice model is coupled with the ocean, but when sea-ice is relaxed to climatology, anomalies occur as zonally symmetric patterns that do not propagate in longitude. Moreover, from the experiment with an active sea-ice component we saw that ACW-like oscillations are strongly modulated by low frequency variability. Our result adds some extra confidence to previous studies based on relatively short series of observed data.
    Description: This research was supported by the PREDICATE EU project (EVK2 – CT-1999 – 0020,). First author was supported by the PRISM EU project (EVR1 – CT-2001 – 40012).
    Description: Published
    Description: 4A. Clima e Oceani
    Description: JCR Journal
    Description: restricted
    Keywords: Antarctic Circumpolar Wave ; General Circulation Models ; air-ice-sea interactions ; 02. Cryosphere::02.04. Sea ice::02.04.01. Atmosphere/sea ice/ocean interaction
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 165
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    An analysis of tropical instability waves in a numerical model of the Pacific Ocean - 2. Generation and energetics of the waves (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The instability processes which generate unstable waves with chara- cteristics similar to observed tropical instability waves in the Pacific Ocean are examined through a local energy analysis based on deviations from the time mean flow. Numerical experiments indicate that the waves develop preferentially in the eastern Pacific along the northern temperature front and have a westward phase speed and a structure with two peaks in amplitude: one located on the equator and the other a few degrees north of it. The energy analysis shows that the "two-peak" structure of the eastern waves is explained by two different instability processes which occur at different latitudes. In the time mean sense the region north of the equator is baroclinically unstable, while barotropic instability prevails at the equator. The life cycle of the waves is revealed by the time evolution of the energetics. Baroclinic instability is the dominant triggering mechanism which induces growth of the waves along the northern temperature front. The eddy pressure fluxes radiate energy south of the equator where the rneridional shear between the Equatorial Undercurrent and the South Equatorial Current becomes barotropically unstable. From the numerical simulations, there is evidence of a second unstable region in the central Pacific south of the equator where the instabilities have a lower phase speed. The energy analysis also shows that these waves grow from both barotropic and baroclinic conversions.
    Description: This work was supported by the Department of Com- merce/NOAA under grant NA56GP0026. One of the au- thors (SM) was partially supported by a NASA Global Change Fellowship NGT-30288. Another author (AB) was supported by a UCAR Postdoctoral Fellowship
    Description: Published
    Description: 29637-29661
    Description: 4A. Clima e Oceani
    Description: JCR Journal
    Description: restricted
    Keywords: Ocean modeling ; Equatorial Ocean ; Tropical Instability Waves ; Ocean wave generation ; Ocean wave energetics ; 03. Hydrosphere::03.01. General::03.01.01. Analytical and numerical modeling
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  • 166
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    Seismo-tectonic behavior of the Pernicana Fault System (Mt Etna): A gauge for volcano flank instability? (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Flank instability at basaltic volcanoes is often related to repeated dike intrusions along rift zones and accompanied by surface fracturing and seismicity. These processes have been mostly studied during specific events, and the lack of longer-term observations hinders their better understanding. Here we analyze ~20 years of deformation of the Pernicana Fault System (PFS), the key structure controlling the instability of the eastern flank of Mt. Etna. We exploit East-West and vertical components of mean deformation velocity, as well as corresponding time series, computed from ERS/ENVISAT (1992–2010) and COSMO-SkyMed (2009–2011) satellite radar sensors via Synthetic Aperture Radar Interferometry techniques. We then integrate and compare this information with field, seismic, and leveling data, collected between 1980 and 2012. We observe transient displacements accompanied by seismicity, overprinted on a long-term background eastward motion (~2 cm/yr). In the last decades, these transient events were preceded by a constant amount of accumulated strain near the PFS. The time of strain accumulation varies between a few years and a few decades, also depending on magma emplacement within the nearby North East Rift, which may increase the strain along the PFS. These results suggest that the amount of deformation near the PFS may be used as a gauge to forecast the occurrence of instability transients on the eastern flank of Etna. In this context, the PFS may provide an ideal, small-scale structure to test the relations between strain accumulation, stress loading, and seismic energy release.
    Description: This work has been partially supported by the Italian Space Agency (ASI) within the SAR4Volcanoes project, agreement I/ 034/11/0.
    Description: Published
    Description: 4398-4409
    Description: 1T. Geodinamica e interno della Terra
    Description: 2T. Tettonica attiva
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: 5T. Sorveglianza sismica e operatività post-terremoto
    Description: 1V. Storia e struttura dei sistemi vulcanici
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: 3V. Dinamiche e scenari eruttivi
    Description: 4V. Vulcani e ambiente
    Description: 6A. Monitoraggio ambientale, sicurezza e territorio
    Description: JCR Journal
    Description: restricted
    Keywords: Volcano flank instability ; Pernicana fault ; Etna ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous ; 04. Solid Earth::04.03. Geodesy::04.03.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous ; 05. General::05.02. Data dissemination::05.02.99. General or miscellaneous ; 05. General::05.08. Risk::05.08.99. General or miscellaneous
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  • 167
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    Complete seismic release of tectonic strain and earthquake recurrence in the Apennines (Italy) (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Here I compare estimates of tectonic strain rates from dense Global Positioning System measurements with the seismicity released in the last ~500 years in the Apennines (Italy). The rates of seismic moment accumulation from geodesy and of historical seismic release by earthquakes agree within the uncertainties, ruling out significant aseismic deformation. Within the considered 400 km long section of the Apennines, this balance yields an average recurrence interval of 30–75 years for MW≥6.5 events without requiring a future earthquake larger than those observed historically (MW~7). A minimum estimate of unreleased strain allows MW≥6.5 and MW≥6.9 events to be released in ~35% and ~10% of the central-southern Apennines, respectively. The definition of the seismic potential for smaller events is more uncertain, and their occurrence remains a significant threat throughout the Apennines.
    Description: Published
    Description: 1155–1162
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: Crustal deformation ; Earthquakes ; GPS ; Apennines ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations
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  • 168
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    Long-term stress-strain analysis of volcano flank instability: The eastern sector of Etna from 1980 to 2012 (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We investigated the evolution of seismicity and deformation in the unstable eastern flank of Etna volcano over a 30 year period (from 1980 to 2012). A significant temporal correlation has been revealed between periods of flank acceleration and intensified seismic activity by comparing seismicity along the northern border (Pernicana fault system) of the sliding flank and the deformation of the eastern flank. Two marked phases have been observed in 1984-1986 and in the years following 2002. These two phases are separated by an intermediate phase from 1987 to 2001, in which the flank sliding slowed down and the seismicity dropped drastically. This common temporal evolution in the deformation rate and seismic release supports the hypothesis that the seismicity in the northern border can be viewed as a marker of the response to accommodate the stress exerted by the traction of the eastern flank sliding. This interplay has also been corroborated by finite element method numerical computations that highlight a good correlation between the seismicity pattern and areas of positive stress changes induced by the sliding surface. The two intense phases of flank acceleration are representative of two main different sources: volcano flank instability stretching the eastern sector in the first 1984-1986 phase and magmatic intrusions pushing the eastern flank seaward since the 2002-2003 eruption. Establishing the relationship between flank acceleration and seismic activation therefore contributes to understanding Etna's mechanical behavior and provides insights into the processes regulating the unstable flank response.
    Description: Published
    Description: 5098-5108
    Description: 1V. Storia e struttura dei sistemi vulcanici
    Description: JCR Journal
    Description: restricted
    Keywords: Pernicana ; fault ; volcano-tectonics ; flank instability ; seismicity and deformation ; stress and strain ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
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  • 169
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    Magma flow between summit and Pu‘u ‘O‘o at Kılauea Volcano, Hawai‘i (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Volcanic eruptions are often accompanied by spatiotemporal migration of ground deformation, a consequence of pressure changes within magma reservoirs and pathways. We modeled the propagation of pressure variations through the east rift zone (ERZ) of K" ılauea Volcano, Hawai‘i, caused by magma " o-Kupaianaha withdrawal during the early eruptive episodes (1983–1985) of the ongoing Pu‘u ‘ O‘" " eruption. Eruptive activity at the Pu‘u ‘ O‘" o vent was typically accompanied by abrupt deflation that lasted for several hours and was followed by a sudden onset of gradual inflation once the eruptive episode had ended. Similar patterns of deflation and inflation were recorded at K" ılauea’s summit, approximately 15 km to the northwest, albeit with time delays of hours. These delay times can be reproduced by modeling the spatiotemporal changes in magma pressure and flow rate within an elastic-walled dike that traverses K" ılauea’s ERZ. Key parameters that affect the behavior of the magma-dike system are the dike dimensions, the elasticity of the wall rock, the magma viscosity, and to a lesser degree the magnitude and duration of the pressure variations themselves. Combinations of these parameters define a transport efficiency and a pressure diffusivity, which vary somewhat from episode to episode, resulting in variations in delay times. The observed variations in transport efficiency are most easily explained by small, localized changes to the geometry of the magma pathway
    Description: Published
    Description: 2232–2246
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: magma flow ; dikes ; Kilauea ; elastic rock ; magma-rock coupling ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous
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  • 170
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    The coupling between very long period seismic events, volcanic tremor, and degassing rates at Mount Etna volcano (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: From December 2005 to January 2006, an anomalous degassing episode was observed at Mount Etna, well-correlated with an increase in volcanic tremor, and in the almost complete absence of eruptive activity. In the same period, more than 10,000 very long period (VLP) events were detected. Through moment tensor inversion analyses of the VLP pulses, we obtained quantitative estimates of the volumetric variations associated with these events. This allowed a quantitative investigation of the relationship between VLP seismic activity, volcanic tremor, and gas emission rate at Mount Etna. We found a statistically significant positive correlation between SO2 gas flux and volcanic tremor, suggesting that tremor amplitude can be used as a first-order proxy for the background degassing activity of the volcano. VLP volumetric changes and SO2 gas flux are correlated only for the last part of our observations, following a slight change in the VLP source depth. We calculate that the gas associated with VLP signal genesis contributed less than 5% of the total gas emission. The existence of a linear correlation between VLP and degassing activities indicates a general relationship between these two processes. The effectiveness of such coupling appears to depend upon the particular location of the VLP source, suggesting that conduit geometry might play a significant role in the VLP-generating process. These results are the first report on Mount Etna of a quantitative relationship between the amounts of gas emissions directly estimated through instrumental flux measurements and the quantities of gas mass inferred in the VLP source inversion.
    Description: Published
    Description: 4910-4921
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Very Long Period seismicity ; UV scanners network ; Etna Volcano ; volcano monitoring ; 04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 171
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    Interaction between magma intrusion and flank dynamics at Mt. Etna in 2008, imaged by integrated dense GPS and DInSAR data (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Global positioning system (GPS) and differential interferometric synthetic aperture radar (DInSAR) data, collected from July 2007 to July 2008 on Mt. Etna, are analyzed to define the dynamics preceding and accompanying the onset of the eruption on 13 May 2008. Short- and long-term comparisons have been made on both GPS and radar data, covering similar time windows. Thanks to the availability of three GPS surveys the year before the eruption onset, an increase in the seaward movement of the NE flank of the volcano has been detected in the few months before the dike intrusion. The GPS ground deformation pattern also shows a slight inflation centered on the western side of the volcano in the preeruptive long-term comparison (from July 2007 to May 2008). The GPS has been integrated with DInSAR data by the SISTEM approach, to take advantage of the different methodologies and provide high spatial sampling of the 3-D ground displacement pattern. We inverted the SISTEM results to model the pressure source causing the observed preeruptive inflation. The subsequent emplacement of the eruptive dike was imaged by two GPS surveys carried out on a dense network over the uppermost part of the volcano on 6 and 13 May, i.e., a few days before and a few hours after the beginning of the eruption. We inverted this comparison to define the position, geometry, and kinematics of the dike. The dike intrusion was also imaged by DInSAR data with temporal baselines of 2-3 months, which confirm strong displacements localized on the summit area, rapidly decreasing toward the middle flanks of the volcano, as detected by very short-term GPS data; furthermore, the comparison between DInSAR and GPS data highlighted the presence of a depressurizing source localized beneath the upper southwestern area, acting just after the dike intrusion. Finally, the long-period (1 year) GPS and DInSAR data were integrated by SISTEM to finely depict the 3-D ground deformation pattern with the highest spatial resolution. The long-period data allowed the complex kinematics of the volcano to be finely imaged and highlighting the interaction between flank dynamics and magma injection.
    Description: Published
    Description: 2818-2835
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: flank dynamics ; eruption ; volcano-tectonics ; GPS ; DInSAR ; data integration ; Etna ; deformation ; volcano ; fault ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 172
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    New data from borehole strainmeters to infer lava fountain sources (Etna 2011-2012) (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: In January 2011 eruptive activity resumed at Etna producing a new phase with frequent lava fountain episodes until April 2012. In November 2011, the first two borehole strainmeters were installed, which detected negative strain changes (~ 0.15 - 0.8 strain) during the paroxysmal events. A Finite Element Model was set up to estimate accurately the tilt and volumetric strain, taking into account the real profile of the volcano and the elastic medium heterogeneity. The numerical computations indicated an elongated depressurizing source located at 0 km b.s.l., which underwent a volume change of ~2 x 106 m3 which is the most of the magma volume erupted while a smaller remaining part is accommodated by the magma compressibility. This shallow source cannot accumulate large magma volumes and, thus, favours short term periodic eruptive events with a fairly constant balance between the refilling and the erupted magma.
    Description: Published
    Description: 3579-3584
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: embargoed_20150613
    Keywords: Etna volcano ; lava fountain eruptions ; shallow plumbing system ; borehole strainmeters ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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  • 173
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    Interseismic coupling, seismic potential, and earthquake recurrence on the southern front of the Eastern Alps (NE Italy) (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Here we use continuous GPS observations to document the geodetic strain accumulation across the South-Eastern Alps (NE Italy). We estimate the interseismic coupling on the intracontinental collision thrust fault and discuss the seismic potential and earthquake recurrence. We invert the GPS velocities using the back slip approach to simultaneously estimate the relative angular velocity and the degree of interseismic coupling on the thrust fault that separates the Eastern Alps and the Venetian-Friulian plain. Comparison between the rigid rotation predicted motion and the shortening observed across the area indicates that the South-Eastern Alpine thrust front absorbs about 70% of the total convergence between the Adria and Eurasia plates. The coupling is computed on a north dipping fault following the continuous external seismogenic thrust front of the South-Eastern Alps. The modeled thrust fault is currently locked from the surface to a depth of ≈10 km. The transition zone between locked and creeping portions of the fault roughly corresponds with the belt of microseismicity parallel and to the north of the mountain front. The estimated moment deficit rate is 1.3 ± 0.4 × 1017 Nm/yr. The comparison between the estimated moment deficit and that released historically by the earthquakes suggests that to account for the moment deficit the following two factors or their combination should be considered: (1) a significant part of the observed interseismic coupling is released aseismically and (2) infrequent “large” events with long return period (〉 1000 years) and with magnitudes larger than the value assigned to the largest historical events (Mw≈ 6.7).
    Description: Published
    Description: 4448-4468
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: Eastern Alps; interseismic coupling; seismotectonics; seismic potential; recurrence time; GPS ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk ; 04. Solid Earth::04.07. Tectonophysics::04.07.01. Continents ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
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  • 174
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    An active oblique-contractional belt at the transition between the Southern Apennines and Calabrian Arc: The Amendolara Ridge, Ionian Sea, Italy (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: High-resolution, single-channel seismic and multibeam bathymetry data collected at the Amendolara Ridge, a key submarine area marking the junction between the Apennine collision belt and the Calabrian subduction forearc, reveal active deformation in a supposedly stable crustal sector. New data, integrated with existing multichannel seismic profiles calibrated with oil-exploratory wells, show that middle to late Pleistocene sediments are deformed in growth folds above blind oblique-reverse faults that bound a regional pop-up. Data analysis indicates that ~10 to 20 km long banks that top the ~80 km long, NW-SE trending ridge are structural culminations above en echelon fault segments. Numeric modeling of bathymetry and stratigraphic markers suggests that three 45° dipping upper crustal (2–10 km) fault segments underlie the ridge, with slip rates up to ~0.5 mm/yr. Segments may be capable with M ~ 6.1–6.3 earthquakes, although an unknown fraction of aseismic slip undoubtedly contributes to deformation. The fault array that bounds the southern flank of the ridge (Amendolara Fault System) parallels a belt of Mw 〈 4.7 strike-slip and thrust earthquakes, which suggest current left-oblique reverse motion on the array. The eastern segment of the array shows apparent morphologic evidence of deformation and might be responsible for Mw ≤ 5.2 historic events. Late Pliocene-Quaternary growth of the oblique contractional belt is related to the combined effects of stalling of Adriatic slab retreat underneath the Apennines and subduction retreat of the Ionian slab underneath Calabria. Deformation localization was controlled by an inherited mechanical interface between the thick Apulian (Adriatic) platform crust and the attenuated Ionian Basin crust.
    Description: Published
    Description: 2169–2194
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: partially_open
    Keywords: Active compression ; Growth strata modeling ; High-resolution seismic ; Multibeam bathymetry ; Jonian Sea ; 04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods ; 04. Solid Earth::04.04. Geology::04.04.01. Earthquake geology and paleoseismology ; 04. Solid Earth::04.04. Geology::04.04.04. Marine geology ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy
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  • 175
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    The initial phases of the 2008–2009 Mount Etna eruption: A multidisciplinary approach for hazard assessment (2011)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Between 2007 and early 2008, the Istituto Nazionale di Geofisica e Vulcanologia (INGV) monitoring networks on Etna volcano recorded a recharging phase that climaxed with a new effusive eruption on 13 May 2008 and lasted about 14 months. A dike‐forming intrusion was accompanied by a violent seismic swarm, with more than 230 events recorded in the first 6 h, the largest being ML = 3.9. In the meanwhile, marked ground deformation was recorded by the permanent tilt and GPS networks, and sudden changes in the summit area were detected by five continuously recording magnetic stations. Poor weather conditions did not allow direct observation of the eruptive events, but important information was provided by infrared satellite images that detected the start of lava fountains from the eruptive fissure, feeding a lava flow. This flow spread within the Valle del Bove depression, covering 6.4 km on the southeastern flank of the volcano in a few hours. The seismicity and deformation pattern indicated that the dike‐forming intrusion was propagating northward. It produced a dry fracture field, which generated concern for the possibility that the eruptive fissures could expand downslope toward populated areas. Monitoring and modeling of the multidisciplinary data, together with the simulations of ash dispersal and lava flows, allowed us both to infer the eruptive mechanisms and to provide correct interpretation of the ongoing phenomena, furnishing useful information for civil defense purposes. We describe how this approach of feedback between monitoring and research provides critical support to risk evaluation.
    Description: We wish to thank all our colleagues from INGV Sezione di Catania for data collection, for the maintenance of the monitoring networks during the whole eruption, and for the many discussions about the interpretation of the eruptive events; the Etna Guides, the Funivia dell’Etna, and especially Alfio Mazzaglia and Nino Mazzaglia for the prompt information pertaining any news about the summit eruptive activity at Mount Etna; the Italian Civil Defense (DPC) for the close and efficient collaboration built up during the last height years of activity at Etna and other Sicilian volcanoes. We obtained MODIS data from NASA and SEVIRI data from EUMETSAT. We are indebted to Paul Davis for his B03203 BONACCORSO ET AL.: ETNA MULTIDISCIPLINARY HAZARD ASSESSMENT B03203 17 of 19 positive and encouraging comments. We thank the Associate Editor Michael P. Ryan, who helped greatly in improving the form of the manuscript. This study was undertaken with partial financial support from the INGV‐DPC 2007–2009 Agreement. Scientific papers funded by DPC do not represent its official opinion and politics. We thank Stephen Conway for revising the English language of this manuscript.
    Description: Published
    Description: B03203
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: reserved
    Keywords: Etna ; effusive eruption ; hazard evaluation ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 176
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    Stochastic models for earthquake triggering of volcanic eruptions (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Many accounts, anecdotal and statistical, have noted a causal effect on volcanic eruptions from large, not too distant, earthquakes. Physical mechanisms have been proposed that explain how small static stress changes, or larger transient dynamic stress changes, can have observable effects on a volcano. While only ∼0.4% of eruptions appear to be directly triggered within a few days of an earthquake, these physical mechanisms also imply the possibility of delayed triggering. In the few regional studies conducted, data issues (selection bias and scarcity, inhomogeneity, and cleaning of data) have tended to obscure any clear signal. Using a perturbation technique, we first show that the Indonesian volcanic region possesses no statistically significant coupling for the region as a whole. We then augment a number of point process models for eruption onsets by a time‐, distance‐, and earthquake magnitude–dependent triggering term and apply this to the individual volcanoes. This method weighs both positive and negative (i.e., absence of eruptions following an earthquake) evidence of triggering. Of 35 volcanoes with at least three eruptions in the study region, seven (Marapi, Talang, Krakatau, Slamet, Ebulobo, Lewotobi, and Ruang) show statistical evidence of triggering over varying temporal and spatial scales, but only after the internal state of the volcano is accounted for. This confirms that triggering is fundamentally a property of the internal magma plumbing of the volcano in question and that any earthquake can potentially “advance the clock” toward a future eruption. This is further supported by the absence of any dependence on triggering of the eruption size
    Description: Published
    Description: B05204
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: earthquake eruption interaction ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
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  • 177
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    UPb and 40Ar39Ar geochronology of Palaeozoic units in the northern Apennines: determining protolith age and alpine evolution using the Calamita Schist and Ortano Porphyroid (2012)
    Wiley
    Details
    Publication Date: 2017-04-04
    Description: In the northern Apennines, the Palaeozoic basement involved in the Late Oligocene–Middle Miocene nappe stack contains metamorphic units for which hypothetical ages have been assigned on the basis of lithological correlations with the Palaeozoic formations of the Variscan chain in Sardinia. This uncertainty concerning the age poses limitations to reconstructing the Palaeozoic stratigraphy, defining the Alpine and pre-Alpine histories and correlations with other domains of the Variscan chain. We present the UPb age of detrital zircon and the 40Ar39Ar age of metamorphic muscovite for the Calamita Schist and Ortano Porphyroid, two metamorphic units of undetermined Palaeozoic age cropping out in the eastern Elba Island. The radioisotopic data allows us to: (i) define the Early Carboniferous and Middle Ordovician ages for the Calamita Schist and Ortano Porphyroid, respectively, as well as their derivation (flysch deposit and magmatic rocks); (ii) pose some constraints concerning their alpine tectonic and metamorphic histories. These new data generate a more precise reconstruction of the Palaeozoic sequence in the northern Apennines, and they document that the Palaeozoic basement involved in the alpine deformation underwent internal stacking with an inversion of the original sequence. Copyright © 2010 John Wiley & Sons, Ltd.
    Description: Published
    Description: 288-310
    Description: 3.2. Tettonica attiva
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: northern Apennines ; Palaeozoic basement ; U-Pb zircon ; 40Ar-39Ar muscovite ; 04. Solid Earth::04.04. Geology::04.04.02. Geochronology ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
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  • 178
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    Total CO2 output from Vulcano Island (Aeolian Islands, Italy) (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-03
    Description: Total CO2 output from fumaroles, soil gas, bubbling gas discharges and water dissolved gases discharged from the island, was estimated for Vulcano island, Italy. The CO2 emission from fumaroles from the La Fossa summit crater was estimated from the SO2 crater output, while CO2 discharged through diffuse soil emission was quantified on the basis of 730 measurements of CO2 fluxes from the soil of the island, performed by using the accumulation chamber method. The results indicate an overall output of ≅500 t/day of CO2 from the island. The main contribution to the total CO2 output comes from the summit area of the La Fossa cone (453 t/day), with 362 t/day from crater fumaroles and 91 t/day from crater soil degassing. The release of CO2 from peripheral areas is ≅20 t/day by soil degassing (Palizzi and Istmo areas mainly), an amount comparable to both the contribution of water dissolved CO2 (6 t/day), as well as to seawater bubbling CO2 (4 t/day measured in the Istmo area). Presented data (September 2007) refer to a period of moderate solphataric activity, when the fumaroles temperature were 450°C and gas/water molar ratio of fumaroles was up to 0.16. The calculated total CO2 emission allows the estimation of the mass release and related thermal energy from the volcanic-hydrothermal system.
    Description: Published
    Description: Q02012
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: JCR Journal
    Description: restricted
    Keywords: CO2 flux, SO2 flux, Vulcano island ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 05. General::05.02. Data dissemination::05.02.01. Geochemical data
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  • 179
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    Fault slip rates for the active External Dinarides thrust-and-fold belt (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We present estimates of slip rates for active faults in the External Dinarides. This thrust-and-fold belt formed in the Adria-Eurasia collision zone by the progressive formation of NE-dipping thrusts in the footwalls of older structures. We calculated the long-term horizontal velocity field, slip rates and related uncertainties for active faults using a thin-shell finite element method. We incorporated active faults with different effective fault frictions, rheological properties, appropriate geodynamic boundary conditions, laterally varying heat flow and topography. The results were obtained by comparing the modeled maximum compressive horizontal stress orientations with the World Stress Map database. The calculated horizontal velocities decrease from the southeastern External Dinarides to the northwestern parts of the thrust-and-fold belt. This spatial pattern is also evident in the long-term slip rates of active faults. The highest slip rate was obtained for the Montenegro active fault, while the lowest rates were obtained for active faults in northwestern Slovenia. Low slip rates, influenced by local active diapirism, are also characteristic for active faults in the offshore central External Dinarides. These findings are contradictory to the concept of Adria as an internally rigid, aseismic lithospheric block because the faults located in its interior release a part of the regional compressive stress. We merged the modeling results and available slip rate estimates to obtain a composite solution for slip rates.
    Description: Published
    Description: TC3019
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: open
    Keywords: External Dinarides ; active fault ; fault friction ; fault slip rate ; rheology ; seismic hazard ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
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  • 180
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    Subsurface structure of the Solfatara volcano (Campi Flegreicaldera, Italy) as deduced from joint seismic-noise array,volcanological and morphostructural analysis (2012)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The joint application of different seismological techniques for seismic noise analysis, and the results of a volcanological and morphostructural survey, have allowed us to obtain a detailed and well constrained image of the shallow crustal structure of the Solfatara volcano (Campi Flegrei caldera, Italy). Horizontal-to-vertical spectral ratios, inversion of surface wave dispersion curves and polarization analysis provided resonance frequencies and peak amplitudes, shear wave velocity profiles and polarization pattern of coherent ambient noise. These results, combined in a unique framework, indicate that the volcanic edifice is characterized by lateral and vertical discontinuities and heterogeneities in terms of shear wave velocity, lithological contrasts and structural setting. The interpretation of the seismological results, with the volcanological and morphostructural constraints, supports the hypothesis that the volcano has been characterized by a complex and intense activity, with the alternation of constructive and destructive phases, during which magmatic and phreatomagmatic explosions built a complex tuff-cone, later reworked by atmospheric agents and altered by hydrothermal activity. The differences in the velocity structure between the central and eastern parts of the crater have been interpreted as resulting from a possible eastward migration of the eruptive vent along the deformational features affecting the area, and to the presence of viscous lava and lithified tuff bodies within the feeding conduits, which are buried under a covering of reworked materials of variable thickness. The observed fault and fracture systems, partially inherited from regional structural setting and exhumed during volcanism and ground deformation episodes also seems to strongly control wave propagation, affecting the noise polarization properties.
    Description: Published
    Description: Q07006
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: partially_open
    Keywords: Solfatara ; crustal structure ; seismic noise ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
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  • 181
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    Heterogeneities along the 2009 L’Aquila normal fault inferred by the b-value distribution (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: In this study we map the distribution of the b-value of the Gutenberg-Richter law—as well as complementary seismicity parameters—along the fault responsible for the 2009 MW 6.1 L'Aquila earthquake. We perform the calculations for two independent aftershock sub-catalogs, before and after a stable magnitude of completeness is reached. We find a substantial spatial variability of the b-values, which range from 0.6 to 1.3 over the fault plane. The comparison between the spatial distribution of the b-values and the main-shock slip pattern shows that the largest slip occurs in normal-to-high b-values portion of the fault plane, while low b-value is observed close to the main-shock nucleation. No substantial differences are found in the b-value computed before and after the main-shock struck in the small region of the fault plane populated by foreshocks.
    Description: Published
    Description: L15304
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: open
    Keywords: L'Aquila earthquake, b-value, heterogeneities, seimicity parameters. ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
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  • 182
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    Wave-guide effects in very high rate GPS record of the 6 April 2009, Mw 6.1 L'Aquila, central Italy earthquake (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: A 10 Hz sampling frequency GPS station was installed near L'Aquila a few days before the 6 April 2009 Mw 6.1 earthquake. It recorded displacement waveforms during the main shock and the largest Mw 5.4 aftershock of 7 April. The horizontal components of the main shock contain a high-amplitude (43 cm peak-to-peak) nearly harmonic (1 Hz) wave train not evident in other nearby instrumental records. The persistency of this feature during aftershocks recorded by a temporarily colocated seismological station highlights a local site effect. Traditional models based on near-surface velocity structure and topography variations fail to reproduce the size and frequency band of the observed amplified motion. The amplified wave train can be explained by a low-velocity fault zone layer below the station. This model fits the delay of the large-amplitude nearly harmonic wave train after the S wave phase and is consistent with the variation in the fault excitation efficiency between the two shocks in relation to their different source depth and location. Synthetic calculation of trapped waves in a model consisting of two quarter spaces separated by a 650 m wide low-velocity zone with 50% velocity reduction and Q value of 20 fit well the observed anomalous record. The parameters of the model fault zone layer are consistent with geological evidence of a broad damage zone adjacent to the station and a similar site response found in this crustal zone with ambient noise. Results of shallow seismic surveys and sonic logs from deep wells provide independent constraints on the host rock velocities.
    Description: This work has partially benefited from the activities performed in the NERA project (Network of European Research infrastructures for earthquake risk Assessment and mitigation, 262330), funded by the European Commission FP7 program, and in the FIRB-Abruzzo project, funded by the Italian Ministery of Education, University and Research.
    Description: Published
    Description: 490–501
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: High-rate GPS ; Transient deformation ; L'Aquila earthquake ; fault-guided waves ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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  • 183
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    Investigation of the complex dynamics and structure of the 2010 Eyjafjallajökull volcanic ash cloud using multispectral images and numerical simulations (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We investigated the structure and evolution of the 2010 Eyjafjallajökull volcanic cloud and its dispersal over Iceland and Europe integrating satellite multispectral images and numerical simulations. Data acquired by Medium Resolution Imaging Spectrometer (MERIS)and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) have been analyzed to quantify the cloud extent and composition. The VOL-CALPUFF dispersal code was applied to reconstruct the transient and 3-D evolution of the cloud. Source parameters estimated on the base of available a posteriori volcanological data sets have been used. Quantitative comparisons between satellite retrievals and modeling results were performed for two selected instants of time during the first and third eruptive phases on a regional scale. Sensitivity of the model to initial volcanological conditions has been analyzed at continental scale. Several complex non intuitive features of cloud dynamics have been highlighted and strengths and limitations of the adopted methods identified. The main findings are: the level of quantitative agreement between satellite observations and numerical results depends on ash cloud composition (particle sizes and concentration) with better agreement for smaller particles and higher concentrations; the agreement between observations and modeling outcomes also depends on the temporal stability of volcanological conditions and the complexity of the meteorological wind field; the irregular dispersion of ash, as reconstructed from satellite data and numerical modeling, can be well explained by the different response of particle sizes to strong vertical wind-shear, and by resuspension processes acting at ground level; eruptive source conditions are the main source of uncertainty in modeling, especially during an ongoing crisis and at long-range scales.
    Description: Published
    Description: 4729–4747
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Volcanic ash cloud ; Satellite retrieval ; Numerical modelling ; Eyjafjallajokull ; Ash dispersal and deposition ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects
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  • 184
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    Major effusive eruptions and recent lava fountains : Balance between expected and erupted magma volumes at Etna volcano (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Over the last four decades Etna has shown a high output rate through numerous eruptions. The volcano has displayed two eruptive behaviors. The first is characterized by effusive eruptions that efficiently drained the storage system and emitted large volumes of magma, the second behavior is related to lava fountains, erupting small magma batches, which are normally with high frequency and have been considered as precursors of major effusive eruptions. In this paper, we present an updated estimation of emitted volumes from Etna eruptions, which include the 38 lava fountain episodes that occurred from January 2011 to April 2013. These recent explosive episodes have been frequent, discharging significant magma volumes. Observing the steady trend of magma output over time, we present insights on expected erupted volumes. We highlight that the January 2011 –April 2013 lava fountains, efficiently drained the intermediate-shallow storage system and favored a balance between the incoming and outgoing magma.
    Description: Published
    Description: 6069–6073
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: open
    Keywords: Eruption mechanisms and flow emplacement ; Volcanic hazards and risks ; volcano monitoring ; erupted volumes ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
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  • 185
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    Vertical GPS ground motion rates in the Euro-Mediterranean region: New evidence of velocity gradients at different spatial scales along the Nubia-Eurasia plate boundary (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We use 2.5 to 14 years long position time series from 〉800 continuous Global Positioning System (GPS) stations to study vertical deformation rates in the Euro-Mediterranean region. We estimate and remove common mode errors in position time series using a principal component analysis, obtaining a significant gain in the signal-to-noise ratio of the displacements data. Following the results of a maximum likelihood estimation analysis, which gives a mean spectral index ~ 0.7, we adopt a power law + white noise stochastic model in estimating the final vertical rates and find 95% of the velocities within ±2 mm/yr, with uncertainties from filtered time series ~40% smaller than from the unfiltered ones. We highlight the presence of statistically significant velocity gradients where the stations density is higher. We find undulations of the vertical velocity field at different spatial scales both in tectonically active regions, like eastern Alps, Apennines, and eastern Mediterranean, and in regions characterized by a low or negligible tectonic activity, like central Iberia and western Alps. A correlation between smooth vertical velocities and topographic features is apparent in many sectors of the study area. Glacial isostatic adjustment and weathering processes do not completely explain the measured rates, and a combination of active tectonics and deep-seated geodynamic processes must be invoked. Excluding areas where localized processes are likely, or where subduction processes may be active, mantle dynamics is the most likely process, but regional mantle modeling is required for a better understanding.
    Description: Published
    Description: 6003–6024
    Description: 1T. Geodinamica e interno della Terra
    Description: 2T. Tettonica attiva
    Description: 1R. Reti di monitoraggio e Osservazioni
    Description: JCR Journal
    Description: restricted
    Keywords: GPS ; Geodynamics ; Mediterranean ; Vertical deformation ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy ; 04. Solid Earth::04.07. Tectonophysics::04.07.01. Continents ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes
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  • 186
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    Deep structure and tectonics of the northern-central Apennines as seen by regional-scale tomography and 3-D located earthquakes (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: In this study we present new high-resolution, regional-scale, Vp and Vp/Vs models of the northern-central Apennines along with accurate 3-D locations of a large set of local earthquakes. The main velocity anomalies are consistent with the surface geology in the shallow layers and present evidence for fluids stored within the basement at greater depths beneath the extensional belt. The Adria and Tyrrhenian mantle are defined by positive velocity anomalies below 30 km depth, while a low-Vp, high-Vp/Vs region in between indicates the existence of a hydrated wedge. The results yield new constraints on active processes in the Apennines and more generally envisage the evolution of a postcollisional belt. Velocity anomalies and earthquakes are consistent with a complex system of delamination and sinking of the Adria continental lithosphere, with the peeling of the crust identified by intermediate-depth seismicity. Change of seismicity and structural patterns along the belt indicates that this tectonic process is diachronous and that fluids, released by sunken lithosphere, are stored within the crust, conditioning the occurrence of seismicity and the onset of extension.
    Description: Published
    Description: 5391-5403
    Description: 1T. Geodinamica e interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Local earthquake tomography ; tectonic of Apennines ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
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  • 187
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    Eruptive processes leading to the most explosive lava fountain at Etna volcano: The 23 November 2013 episode (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The 23 November 2013 lava fountain at Etna volcano was the most explosive of the last 44 episodes that have occurred at Etna in 2011–2013. We infer the total magma volume erupted by thermal images analysis and show that it was characterized by a very high time-averaged-discharge-rate (TADR) of ~360m3 s 1, having erupted ~1.6 × 106m3 of dense-rock equivalent magma volume in just 45 min, which is more than 3 times the TADR observed during previous episodes. Two borehole dilatometers confirmed the eruption dynamics inferred from the thermal images. When compared to the other lava fountains, this episode can be considered as the explosive end-member. However, the erupted volume was still comparable to the other lava fountain events. We interpret that the 23 November explosive end-member event was caused by more primitive and gas-rich magma entering the system, as demonstrated by the exceptional height reached by the lava fountain.
    Description: Published
    Description: 4912–4919
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Etna eruption ; paroxysmal explosive eruption ; lava fountain ; strainmeters ; lava fountain volume ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 188
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    Progression of spontaneous in-plane shear faults from sub-Rayleigh to compressional wave rupture speeds (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We investigate numerically the passage of spontaneous, dynamic in-plane shear ruptures from initiation to their final rupture speed, using very fine grids. By carrying out more than 120 simulations, we identify two different mechanisms controlling supershear transition. For relatively weaker faults, the rupture speed always passes smoothly and continuously through the range of speeds between the Rayleigh and shear wave speeds (the formerly considered forbidden zone of rupture speeds). This, however, occurs in a very short time, before the ruptures reach the compressional wave speed. The very short time spent in this range of speeds may explain why a jump over these speeds was seen in some earlier numerical and experimental studies and confirms that this speed range is an unstable range, as predicted analytically for steady state, singular cracks. On the other hand, for relatively stronger faults, we find that a daughter rupture is initiated by the main (mother) rupture, ahead of it. The mother rupture continues to propagate at sub-Rayleigh speed and eventually merges with the daughter rupture, whose speed jumps over the Rayleigh to shear wave speed range. We find that this daughter rupture is essentially a “pseudorupture,” in that the two sides of the fault are already separated, but the rupture has negligible slip and slip velocity. After the mother rupture merges with it, the slip, the slip velocity, and the rupture speed become dominated by those of the mother rupture. The results are independent of grid sizes and of methods used to nucleate the initial rupture.
    Description: Published
    Description: 8331–8345
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: open
    Keywords: Seismic source ; Supershear ruptures ; 04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones
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  • 189
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    Testing the IONORT-ISP system: A comparison between synthesized and measured oblique ionograms (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The three-dimensional (3-D) electron density representation of the ionosphere computed by the assimilative IRI-SIRMUP-P (ISP) model was tested using IONORT (IONOspheric Ray-Tracing), a software application for calculating a 3-D ray-tracing for high frequency (HF) waves in the ionospheric medium. A radio link was established between Rome (41.8°N, 12.5°E) in Italy, and Chania (35.7°N, 24.0°E) in Greece, within the ISP validity area, and for which oblique soundings are conducted. The ionospheric reference stations, from which the autoscaled foF2 and M(3000)F2 data and real-time vertical electron density profiles were assimilated by the ISP model, were Rome (41.8°N, 12.5°E) and Gibilmanna (37.9°N, 14.0°E) in Italy, and Athens (38.0°N, 23.5°E) in Greece. IONORT was used, in conjunction with the ISP and the International Reference Ionosphere (IRI) 3-D electron density grids, to synthesize oblique ionograms. The comparison between synthesized and measured oblique ionograms, both in terms of the ionogram shape and the maximum usable frequency characterizing the radio path, demonstrates both that the ISP model can more accurately represent real conditions in the ionosphere than the IRI, and that the ray-tracing results computed by IONORT are reasonably reliable.
    Description: Published
    Description: 167–179
    Description: 1.7. Osservazioni di alta e media atmosfera
    Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale
    Description: 5.4. Banche dati di geomagnetismo, aeronomia, clima e ambiente
    Description: JCR Journal
    Description: partially_open
    Keywords: Electron Density ; Ray-Tracing ; Oblique Ionogram ; IRI ; Assimilative Modelling ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous ; 01. Atmosphere::01.02. Ionosphere::01.02.04. Plasma Physics ; 01. Atmosphere::01.02. Ionosphere::01.02.05. Wave propagation ; 01. Atmosphere::01.02. Ionosphere::01.02.06. Instruments and techniques ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous ; 05. General::05.01. Computational geophysics::05.01.01. Data processing ; 05. General::05.01. Computational geophysics::05.01.03. Inverse methods
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  • 190
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    Geochemical insight into differences in the physical structures and dynamics of two adjacent maar lakes at Mt. Vulture volcano (southern Italy) (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We report on the first geochemical investigation of the Monticchio maar lakes (Mt. Vulture volcano, southern Italy) covering an annual cycle that aimed at understanding the characteristic features of the physical structures and dynamics of the two lakes. We provide the first detailed description of the lakes based on high-resolution CTD profiles, chemical and isotopic (H and O) compositions of the water, and the amounts of dissolved gases (e.g., He, Ar, CH4 and CO2). The combined data set reveals that the two lakes, which are separated by less than 200 m, exhibit different dynamics: one is a meromictic lake, where the waters are rich in biogenic and mantle-derived gases, while the other is a monomictic lake, which exhibits complete turnover of the water in winter and the release of dissolved gases. Our data strongly suggest that the differences in the dynamics of the two lakes are due to different density profiles affected by dissolved solutes, mainly Fe, which is strongly enriched in the deep water of the meromictic lake. A conceptual model of water balance was constructed based on the correlation between the chemical composition of the water and the hydrogen isotopic signature. Gas-rich groundwaters that feed both of the lakes and evaporation processes subsequently modify the water chemistry of the lakes. Our data highlight that no further potential hazardous accumulation of lethal gases is expected at the Monticchio lakes. Nevertheless, geochemical monitoring is needed to prevent the possibility of vigorous gas releases that have previously occurred in historical time.
    Description: Published
    Description: 1411–1434
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: JCR Journal
    Description: restricted
    Keywords: geochemistry ; noble gases ; maar lake ; lake dynamics ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
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  • 191
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    The Ainsa Fold and thrust oblique zone of the central Pyrenees: Kinematics of a curved contractional system from paleomagnetic and structural data (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Integration of structural, stratigraphic, and paleomagnetic data from the N–S trending structures of the Ainsa Oblique Zone reveals the kinematics of the major thrust salient in the central Pyrenees. These structures experienced clockwise vertical axis rotations that vary from 70° in the east (Mediano anticline) to 55° in the west (Boltaña anticline). Clockwise vertical axis rotations of 60° to 45° occurred from early Lutetian to late Bartonian when the folds and thrusts of the Ainsa Oblique Zone developed. This vertical axis rotation stage resulted from a difference of about 50 km in the amount of displacement on the Gavarnie thrust and an accompanying change in structural style at crustal scale from the central to the western Pyrenees, related to the NE–SW trending pinch out of Triassic evaporites at its basal detachment. A second rotation event of at least 10° took place since Priabonian, as a result of a greater displacement of the Serres Marginals thrust sheet with respect to the Gavarnie thrust sheet above the Upper Eocene-Oligocene salts. The deduced kinematics demonstrates that the orogenic curvature of the central Pyrenees is a progressive curvature resulting from divergent thrust transport direction. Layer parallel shortening mesostructures and kilometer-scale folds also developed by a progressive curvature related to divergent shortening directions during vertical axis rotation. Rotation space problems were solved by along-strike extension which triggered the formation of transverse extensional faults and diapirs at the outer arcs of structural bends.
    Description: Published
    Description: 1142–1175
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: JCR Journal
    Description: restricted
    Keywords: vertical-axis rotation ; thrust-sheet ; Eocene ; orogen ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
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  • 192
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    Deformed Pleistocene marine terraces along the Ionian sea margin of southern Italy: unveiling blind fault-related folds contribution to coastal uplift (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Morphotectonic analysis and fault numeric modeling of uplifted marine terraces along the Ionian Sea coast of the Southern Apennines allowed us to place quantitative constraints on middle Pleistocene-Holocene deformation. Ten terrace orders uplifted to as much as +660 m were mapped along ~80 km of the Taranto Gulf coastline. The shorelines document both a regional and a local, fault-induced contribution to uplift. The intermingling between the two deformation sources is attested by three 10 km scale undulations superimposed on a 100 km scale northeastward tilt. The undulations spatially coincide with the trace of NW-SE striking transpressional faults that affected the coastal range during the early Pleistocene. To test whether fault activity continued to the present, we modeled the differential uplift of marine terraces as progressive elastic displacement above blind oblique-thrust ramps seated beneath the coast. Through an iterative and mathematically based procedure, we defined the best geometric and kinematic fault parameters as well as the number and position of fault segments. Fault numerical models predict two fault-propagation folds cored by blind thrusts with slip rates ranging from 0.5 to 0.7 mm/yr and capable of generating an earthquake with a maximum moment magnitude of 5.9–6.3. Notably, we find that the locus of predominant activity has repeatedly shifted between the two fault systems during time and that slip rates on each fault have temporally changed. It is not clear if the active deformation is seismogenic or dominated by aseismic creep; however, the modeled faults are embedded in an offshore transpressional belt that may have sourced historical earthquakes.
    Description: Published
    Description: 737-762
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: partially_open
    Keywords: uplifted marine terraces ; fault modeling ; fault-propagation folds ; middle-late Pleistocene ; active transpression ; Southern Italy ; 04. Solid Earth::04.04. Geology::04.04.01. Earthquake geology and paleoseismology ; 04. Solid Earth::04.04. Geology::04.04.03. Geomorphology ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology
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  • 193
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    Hints on the deformation penetration induced by subductions and collision processes: Seismic anisotropy beneath the Adria region (Central Mediterranean) (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Adria is a small region surrounded by three mountain belts: the Alps, the Apennines, and the Dinarides, built up by long evolution of subduction and collisional systems. We present 253 shear wave splitting measurements obtained by studying more than 100 teleseismic events for 12 stations. SKS splitting measurements show 3-D complexity and quite strong upper mantle deformation. We carefully analyzed results in terms of back azimuthal coverage and interpret measurements as related to Adria rotation and to subductions evolution. In the northern part of Adria, the anisotropy pattern follows the arcuate shape of the Alps; the same pattern, parallel to the mountains, occurs along the Apennines, but fast directions show a sudden change in the Adria foreland. This lateral variation has been analyzed to isolate a distinct Adria mantle anisotropic pattern, which is identified as NE-SW fast direction along the western microplate boundary and as N-S fast direction at Trieste. This pattern might be induced by drag effect of the counterclockwise rotation of Adria lithosphere that behaves as an independent microplate as identified by GPS data. Our measurements suggest that the geodynamic process that generated the Alps is more efficient deforming a larger volume of mantle than its Apennine counterpart. Moreover, the mantle circulation we hypothesize looking at the regional-scale patterns of anisotropy requires the existence of an escape route beneath the Alps-Apennines transition, through which the mantle flows and feed circulation in the Tyrrhenian mantle system as suggested by previous geodynamic models and as seen by some tomographic studies.
    Description: Published
    Description: 5814–5826
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Seismic Anisotropy ; Adriatic region ; 04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes ; 05. General::05.02. Data dissemination::05.02.02. Seismological data
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  • 194
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    Paleomagnetic evidence for a post-Eocene 90° CCW rotation of internal Apennine units: A linkage with Corsica-Sardinia rotation? (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-10-06
    Description: We report on an extensive paleomagnetic study (36 sites) of the Tuscan Nappe succession from the Northern Apennines Arc, aimed to reconstruct the tectonic evolution of the internal sector of this chain. We analyzed Eocene pelagic foreland ramp deposits (Scaglia Toscana Formation) and Oligocene–lower Miocene siliciclastic turbidites (Macigno and Falterona Formations). Paleomagnetic results show that the internal sector of the Northern Apennines underwent large counterclockwise (CCW) rotations with respect to the Adria-Africa foreland. A decrease in the rotation magnitude was observed from the southern to the northern sector of the arc (from 91 to 36°). This trend is opposite to that observed in the more external units of Northern Apennines and demonstrates that the oroclinal bending model, which has been proposed for the external units of the chain, is not appropriate to explain the evolution of the internal sector of the arc. On the basis of the observed paleomagnetic pattern, we propose a new tectonic model in which the Tuscan and Falterona-Cervarola units in the southern area were first rotated CCW along with the Corsica-Sardinia block during its lower Miocene rotational drifting and were later involved in the main phases of rotational emplacement and translation toward the outermost sector (Umbria domain), thus yielding the final curved shape of the Northern Apennines chain. Data from this study represent the first paleomagnetic evidence of the influence of the Corsica-Sardinia CCW rotation in the Apennines orogenic wedge deformation, in the general framework of the geodynamic evolution of the Central Mediterranean subduction system.
    Description: Published
    Description: 374-392
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: paleomagnetism, Apennines, Tuscany ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism
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  • 195
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    Seismovolcanic signals at Deception Island volcano,Antarctica: Wave field analysis and source modeling (2011)
    American Geophysical Union
    Details
    Publication Date: 2017-11-17
    Description: Island (Antarctica), recorded during three Antarctic summers (1994- 1995, 1995-1996 and 1996-1997), are analyzed using a dense small-aperture (500 m) seismic array. The visual and spectral classification of the seismic events shows the existence of long-period and hybrid isolated seismic events, and of low-frequency, quasi-monochromatic and spasmodic continuous tremors, All spectra have the highest amplitudes in the frequency band between 1 and 4 Hz, while hybrids and spasmodic tremors have also significant amplitudes in the high-frequency band (4-10 Hz). The array analysis indicates that almost all the well-correlated low-frequency signals share similar array parameters (slowness and back azimuth) and have the same source area, close to the array site. The polarization analysis shows that phases at high-frequency are mostly composed of P waves, and those phases dominated by low frequencies can be interpreted as surface waves. No clear shear waves are evidenced. From the energy evaluation, we have found that the reduced displacement values for surface and body waves are confined in a narrow interval. Volcano-tectonic seismicity is located close to the array, at a depth shallower than 1 km. The wave-field properties of the seismovolcanic signals allow us to assume a unique source model, a shallow resonating fluid-filled crack system at a depth of some hundreds of meters. All of the seismic activity is interpreted as the response of a reasonably stable stationary geothermal process. The differences observed in the back azimuth between low and high frequencies are a near-field effect. A few episodes of the degassification process in an open conduit were observed and modeled with a simple organ pipe.
    Description: Published
    Description: 13905-13931
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Long Period Events ; Deception Island ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
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  • 196
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    A Holocene paleosecular variation record from the northwestern Barents Sea continental margin (2011)
    American Geophysical Union
    Details
    Publication Date: 2019-06-17
    Description: A high‐resolution paleomagnetic and rock magnetic study has been carried out on sediment cores collected in glaciomarine silty‐clay sequences from the continental shelf and slope of the southern Storfjorden trough‐mouth fan, on the northwestern Barents Sea continental margin. The Storfjorden sedimentary system was investigated during the SVAIS and EGLACOM cruises, when 10 gravity cores, with a variable length from 1.03 m to 6.41 m, were retrieved. Accelerator mass spectrometry (AMS) 14C analyses on 24 samples indicate that the cores span a time interval that includes the Holocene, the last deglaciation phase and in some cores the last glacial maximum. The sediments carry a well‐defined characteristic remanent magnetization and have a valuable potential to reconstruct the paleosecular variation (PSV) of the geomagnetic field, including relative paleointensity (RPI) variations. The paleomagnetic data allow reconstruction of past dynamics and amplitude of the geomagnetic field variations at high northern latitudes (75°–76° N). At the same time, the rock magnetic and paleomagnetic data allow a high‐resolution correlation of the sedimentary sequences and a refinement of their preliminary age models. The Holocene PSV and RPI records appear particularly sound, since they are consistent between cores and they can be correlated to the closest regional stacking curves (UK PSV, FENNOSTACK and FENNORPIS) and global geomagnetic model for the last 7 ka (CALS7k.2). The computed amplitude of secular variation is lower than that outlined by some geomagnetic field models, suggesting that it has been almost independent from latitude during the Holocene.
    Description: Published
    Description: Q11Z33
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: Barents Sea ; Holocene ; Storfjorden ; geomagnetic paleosecular variation ; relative paleointensity ; 04. Solid Earth::04.05. Geomagnetism::04.05.01. Dynamo theory ; 04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals ; 04. Solid Earth::04.05. Geomagnetism::04.05.05. Main geomagnetic field ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism
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  • 197
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    Explosive expansion of a slowly-decompressed magma analog:evidence of delayed bubble nucleation (2014)
    American Geophysical Union
    Details
    Publication Date: 2019-12-05
    Description: While ascending in the plumbing system of volcanoes, magma undergoes decompression at rates spanning several orders of magnitude and set by a number of factors internal and external to the volcano. Slow decompression generally results in an effusive or mildly explosive expansion of the magma, but counterexamples of sudden switches from effusive to explosive eruptive behaviour have been documented at various volcanoes worldwide. The mechanisms involved in this behavior are currently debated, in particular regarding basaltic magmas. Here, we explore the interplay between decompression rate and vesiculation vigour by decompressing a magma analog obtained by dissolving pine resin into acetone in varying proportions. Our mixtures contain solid particles and upon decompression experience the nucleation of acetone bubbles. We find mixtures high in acetone, containing smaller and fewer solid particles, experience strong supersaturation and fragment for very slow decompressions, despite having low viscosity, while mixtures low in acetone, with more and larger solid particles degas efficiently. We interpret our results in terms of delayed bubble nucleation due to a lack of efficient nucleation sites. We discuss how a similar mechanism might induce violent, explosive expansion in volatile-rich and poorly crystalline low-silica magmas, by analogy to previous inferences for rhyolitic magmas.
    Description: Published
    Description: 3067-3084
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: embargoed_20150613
    Keywords: Magma fragmentation ; basaltic magma ; analog laboratory experiments ; slow decompression ; bubble nucleation ; explosive volcanic eruptions ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism
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  • 198
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    Laboratory measurements of the frictional properties of the Zuccale low-angle normal fault, Elba Island, Italy (2011)
    American Geophysical Union
    Details
    Publication Date: 2020-02-24
    Description: Using a case study from the island of Elba, Italy, we seek to test the hypothesis that the presence of minerals with low frictional strengths can explain prolonged slip on low-angle normal faults. The central core of the Zuccale low-angle normal fault contains a distinctive fault rock zonation that developed during progressive exhumation. Most fault rock components preserve microstructural evidence for having accommodated deformation entirely, or partly, by frictional mechanisms. One millimeter thick sample powders of all the major fault rock components were deformed in a triaxial deformation apparatus under water-saturated conditions, at room temperature, and at constant effective normal stresses of 25, 50, and 75 MPa. Pore fluid pressure was maintained at 50 MPa throughout. Overall, the coefficient of friction (m) of the fault rocks varies between 0.25 and 0.8, emphasizing the marked strength heterogeneity that may exist within natural fault zones. Also, m is strongly dependent on fault rock mineralogy and is 〈0.45 for fault rocks containing talc, chlorite, and kaolinite and 〉0.6 for fault rocks dominated by quartz, dolomite, calcite, and amphibole. Localization of frictional slip within talc-rich portions of the fault core can potentially explain movements along the Zuccale fault over a wide range of depths within the upper crust, although the mechanical importance of the talc-bearing fault rocks likely decreased following their dismemberment into a series of poorly connected fault rock lenses. Additionally, slip within clay-bearing fault gouges with m between 0.4 and 0.5 may have facilitated movements in the uppermost (〈2 km) crust. For several other fault rock components, m varies between 0.5 and 0.8, and mineralogical weakening alone is insufficient to account for low-angle slip. In the latter fault rock components, other weakening mechanisms such as the development of high fluid pressures, or dissolution-precipitation creep, may have been particularly important in reducing fault strength.
    Description: Published
    Description: B02407
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: Friction ; Low-Angle Normal Fault ; Elba ; Zuccale Fault ; Microstructure ; 04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 199
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    Comment on “The winter anomaly in the middlelatitude F region during the solar minimum period observed by the Constellation Observing System for Meteorology, Ionosphere, and Climate” by W. K. Lee, H. Kil, Y.-S. Kwak, Q. Wu, S. Cho, and J. U. Park (2014)
    American Geophysical Union
    Details
    Publication Date: 2020-02-24
    Description: Seasonal or winter anomaly in the F2 layer has been known since the beginning of regular ionospheric observations [e.g., Berkner and Wells, 1938, and references therein], and one may be sure that such a fundamental feature of this phenomenon as its height extent has been analyzed. However, Lee et al. [2011] using radio occultation Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Ne(h) observations have decided to reconsider this problem starting from the very beginning without any analyses of previous investigations and comparisons to earlier obtained results as if ionospheric F2 layer physics has started with them. Besides, the authors have done some incorrect statements which contradict the present theory of the ionospheric F2 layer. They claim that “The topside plasma density is greater in the summer hemisphere than in the winter hemisphere; … the electron density below the F peak at middle latitudes is also greater during summer than during winter; Therefore, the seasonal anomalous behavior is a phenomenon only near the F-peak height in the Northern Hemisphere; The question is why the seasonal behavior of the ionosphere near the F-peak height is different from the behavior below and above the F peak. ….there was no explanation for the different seasonal behaviors of electron density in the lower F region and at F-peak height”. This is the main contents and results of the paper. Let us consider what was known about winter anomaly before the paper by Lee et al. [2011].
    Description: Published
    Description: 7972–7978
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Description: restricted
    Keywords: December anomaly, ionosphere ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 200
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    A completeness analysis of the national seismic network of Italy (2010)
    American Geophysical Union
    Details
    Publication Date: 2020-02-24
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: We present the first detailed study of earthquake detection capabilities of the Italian National Seismic Network and of the completeness threshold of its earthquake catalog. The network in its present form started operating on 16 April 2005 and is a significant improvement over the previous networks. For our analysis, we employed the PMC method as introduced by Schorlemmer and Woessner (2008). This method does not estimate completeness from earthquakes samples as traditional methods, mostly based on the linearity of earthquake-size distributions. It derives detection capabilities for each station of the network and synthesizes them into maps of detection probabilities for earthquakes of a given magnitude. Thus, this method avoids the many assumptions about earthquake distributions that traditional methods make. The results show that the Italian National Seismic Network is complete at M=2.9 for the entire territory excluding the islands of Sardinia, Pantelleria, and Lampedusa. At the M=2.5 level, which is the reporting threshold level of the Italian Civil Protection, the network may miss events in southern parts of Apulia and the western part of Sicily. The stations are connected through many different telemetry links to the operational datacenter in Rome. Scenario computations show that no significant drop in completeness occurs if one of the three major links fail, indicating a well-balanced network setup.
    Description: Published
    Description: B04308
    Description: 5.2. TTC - Banche dati di sismologia strumentale
    Description: JCR Journal
    Description: open
    Keywords: Completeness Analysis ; Italian Seismicity ; Minimum Magnitude of Completeness ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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