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  • Articles  (21)
  • 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology  (13)
  • 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution  (8)
  • Elsevier  (21)
  • American Chemical Society
  • American Chemical Society (ACS)
  • 2010-2014  (21)
  • 1985-1989
  • 1980-1984
  • 1950-1954
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  • Articles  (21)
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  • 2010-2014  (21)
  • 1985-1989
  • 1980-1984
  • 1950-1954
  • 2005-2009  (33)
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  • 1
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    Seasonal cycles of seismic velocity variations detected using coda wave interferometry at Fogo volcano, São Miguel, Azores, during 2003–2004 (2010)
    Elsevier
    Details
    Publication Date: 2020-11-12
    Description: Fogo volcano is an active central volcano, with a lake filled caldera, in the central part of São Miguel Island, Azores, whose current activity is limited to hydrothermal manifestations such as active fumarolic fields, thermal and CO2 cold springs and soil diffuse degassing areas. It is affected by important active tectonic structures, with high seismic activity and practically continuous micro-seismicity. A recurrent feature from the seismicity observed in volcanic regions is the occurrence of clusters of similar earthquakes, whose origin can be attributed to the repeated action of a similar source mechanism at the same focal area. Doublets/multiplets were identified in this study within a catalogue of small magnitude (usually 〈 3) volcano tectonic events recorded in 2003–2004 by a selection of stations around Fogo volcano. All events have been cross-correlated and pairs whose waveforms exhibited a cross-correlation coefficient equal to or higher than 0.9 were analysed using the coda-wave interferometry technique. Subtle velocity variations found between events highlight a seasonal cycle of the velocity patterns, with lower velocity in winter time and higher velocity during summer months. Those results, together with quantitative differences between the same doublets at different stations, exhibit an excellent correlation with rainfall. A seasonal effect can also be broadly seen in the seismicity occurrence, and some of the swarms recorded over the two year period occur during the wettest season or close to episodes of abundant (above average) rainfall. Moreover, temporal and spatial analysis of several swarms highlighted the lack of any mainshock–aftershock sequence and organized migration of the hypocenters. This is suggestive of a very heterogeneous stress field. Vp/Vs is found to be lower than usually observed in volcanic areas, an occurrence likely related to the presence of steamy fluid associated with the geothermal system. Taken together, these observations suggest that pore pressurisation plays a major role in controlling a considerable part of the recorded seismicity. The geothermal fluids around Fogo massif have been identified as derived from meteoric water, which infiltrates through Fogo Lake and the volcano flanks and flows from south to north on the northern flank. All those elements seem to point to a role played by rainfall in triggering seismicity at São Miguel, possibly through pressure changes at depth in response to surface rain and/or an interaction with the geothermal system.
    Description: Published
    Description: 231-246
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: velocity changes ; rainfall ; volcano seismicity ; triggered seismicity ; Azores archipelago ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Strain accumulation across the Messina Straits and kinematics of Sicily and Calabria from GPS data and dislocation modeling (2011)
    Elsevier
    Details
    Publication Date: 2020-12-03
    Description: We use Global Positioning System (GPS) velocities and dislocation modeling to investigate the rate and nature of interseismic strain accumulation in the area affected by the 1908 Mw 7.1 Messina earthquake (southern Italy) within the framework of the complex central Mediterranean microplate kinematics. Our data confirm a change in the velocity trends between Sicily and Calabria, moving from NNW-ward to NE- ward with respect to Eurasia, and detail a fan-like pattern across the Messina Straits where maximum extensional strain rates are ~65 nanostrains/yr. Extension normal to the coast of northern Sicily is consistent with the presence of SW–NE trending normal faults. Half-space dislocation models of the GPS velocities are used to infer the slip-rates and geometric fault parameters of the fault zone that ruptured in the Messina − 1.3 earthquake. The inversion, and the bootstrap analysis of model uncertainties, finds optimal values of 3. 5 + 2.0 − 0.2− 0.7 and 1.6 + 0.3 mm/yr for the dip–slip and strike–slip components, respectively, along a 30 + 1.1° SE-ward dipping normal fault, locked above 7.6−2.9 km depth. By developing a regional elastic block model that + 4.6 accounts for both crustal block rotations and strain loading at block-bounding faults, and adopting two different competing models for the Ionian–Calabria convergence rates, we show that the measured velocity gradient across the Messina Straits may be significantly affected by the elastic strain contribution from other nearby faults. In particular, when considering the contribution of the possibly locked Calabrian subduction interface onto the observed velocity gradients in NE-Sicily and western Calabria, we find that this longer wavelength signal can be presently super-imposed on the observed velocity gradients in NE-Sicily and Calabria. The inferred slip-rate on the Messina Fault is significantly impacted by elastic strain from the subduction thrust. By varying the locking of the subduction thrust fault, in fact, the Messina Fault slip-rate varies from 0 to 9 mm/yr.
    Description: Published
    Description: 347-360
    Description: 1.9. Rete GPS nazionale
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: open
    Keywords: Messina Straits ; Global Positioning System ; strain accumulation ; plate kinematics ; dislocation modeling ; 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::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk ; 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
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
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    Tornillos at Vulcano: Clues to the dynamics of the hydrothermal system (2010)
    Elsevier
    Details
    Publication Date: 2020-11-12
    Description: The number of tornillo events has recently increased at the Vulcano Island, Italy. While only 15 tornillos were recorded during 2004–2006, 584 events occurred in 2007–2008. They were located just below La Fossa Crater at depths ranging between 0.1 and 1 km b.s.l. During two intervals in 2007–2008 increases in the number of tornillos took place at the same time as temperature and geochemical anomalies were observed. The spectral content of the tornillos, generally characterized by one–two dominant spectral peaks near 6 and 10 Hz, varied over time, with changes also noted in the quality factors. The simplest source mechanism proposed for tornillos is the free eigenvibration of a fluid volume within a crack or a conduit. Based on this model, we propose a causal relationship between the temperature and geochemical anomalies and the increases in numbers of tornillos. As the amount of hydrothermal fluids increases during the anomalies, the upward flux of fluids grows. The consequent changes in the pressure, temperature and dynamics of the system of cracks and conduits result in the generation of tornillos. Based on the fluid-filled crack/conduit model, the shallow depths of the sources and the values of the quality factors, the fluid within the resonant crack/conduit was inferred to be an ash–gas or water droplet–gas mixture. Moreover, the observed variations in the wavefield can be caused by small changes in the location of the source, in the source mechanism, or in the medium in between the source and the seismic station. Finally, another peculiar feature of tornillos is the amplitude modulation that can be explained as a result of a beating phenomenon.
    Description: Published
    Description: 377-393
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Description: JCR Journal
    Description: reserved
    Keywords: Tornillos ; Vulcano Island ; Hydrothermal system ; Volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
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    Analysis of the 9 September 1998 Mw 5.6 Mercure earthquake sequence (Southern Apennines, Italy): A multidisciplinary approach (2012)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: The Mercure earthquake (Mw 5.6) of September 9, 1998 and the associated aftershocks occurred in a small Pleistocene–Holocene continental basin of the Southern Apennines, in a region of low instrumental and moderate historical seismicity. Seismological, photogeological and field survey data were analyzed and integrated in order to identify the likely seismogenic structure, to depict its 3-D geometry and kinematics and to provide further constraints to the seismogenic potential of the rupture processes in the study area. The mainshock occurred at the NW edge of the seismic sequence (40.03°N and 15.95°) at a depth of 10.5± 1.5 km. The aftershocks volume was determined from the relocation of about 200 events (1.1=Ml=3.9) registered by local networks from September 10 to October 12, 1998. The relocation procedure was based on choosing P and S waves for all the events and the definition of ten 9-layers velocity models appropriate for the different stations. The kinematics of the seismogenic deformation was defined through the computation of 36 well-constrained focal mechanisms. The seismological and geological stress tensors were determined through inversion of focal mechanisms and fault slip data. Both of them resulted in the tensional type, with ENE–WSW and NE–SW trending σ3 axis, respectively. The map and the section distribution of the aftershocks sequence depicts an average NW–SE striking and 60° SW-dipping seismogenic volume. Most of the events (80%) were located at depths between 3 and 8 km in the footwall of the Mercure basin (MBB) boundary fault but along the possible down-dip continuation of a previously unidentified, N120°E striking and WSW-dipping, Holocene normal fault alignment, which extends from Castello Seluci to Piana Perretti and Timpa della Manca (CPST fault). A small percentage of events (10%) were located at depths between 10 and 12 km where the CPST seismogenic fault may detach. The reconstructed rupture area (RA) of the Mercure 1998 earthquake has an along-strike length (L) of about 9 km and a down-dip width (W) of about 9 km, yielding a total area of approximately 81 km2 . On the other hand, the L and W dimension of the entire individual seismogenic structure identified as responsible for the earthquake, e.g. the CPST fault, are about 19 and 12 km, respectively, with a consequent RA of about 230 km2 . This may imply a maximum magnitude (Mw) equal to 6.3 which lead us to compare the Mercure area, in terms of seismogenic hazard, to the adjacent Pollino-Castrovillari area where strong paleoseismological events are documented.
    Description: Published
    Description: 210–225
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: Southern Apennines ; Stress-distribution ; Earthquake location ; Seismotectonics ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
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    Velocity and attenuation tomography of the Umbria Marche 1997 fault system: Evidence of a fluid-governed seismic sequence (2010)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: The 1997 Umbria Marche is probably the best ever monitored normal faulting seismic sequence. Seismicity migration and multiple main shocks characterize the activation of a 40-km-long system of contiguous fault segments, as documented by seismological data. Many authors as indicative of fault weakening by fluids migration have interpreted this behaviour. In this study, we create a new catalogue of high quality P- and S-wave arrival times merging data recorded by permanent and temporary stations to improve the resolution of velocity and attenuation models and earthquake locations. We show that the relocated earthquakes and the joint interpretation of P- and S-wave velocity and attenuation models help in understanding the faulting processes, revealing new details of the geometry of the main faults and physical state of fluids within the crustal volume. We observe that large aftershocks occur on the top and within the Triassic evaporitic layer, a rock volume locally characterised by fluid over-pressured, as evidenced by high VP/VS and low QP/QS anomalies. Velocity and attenuation heterogeneities are evidence that the migration of fluid pressure along the fault system is the driving mechanism of the prolonged earthquake sequence.
    Description: Published
    Description: 73-84
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: JCR Journal
    Description: reserved
    Keywords: Velocity and Attenuation tomography ; Normal fault system ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    Analysis of small magnitude seismic sequences along the Northern Apennines (Italy) (2010)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: We analyze the seismicity of a small sector of the Northern Apennines merging data from the Italian seismic bulletin with original data collected by temporary seismic networks. Our attention is focused on the region enclosed between the Apenninic watershed and the Adriatic Sea. This portion of belt is interested by the occurrence of diffuse crustal seismicity and small-to-moderate earthquakes. In this paper we study the five small sequences with mainshock having Mw 〈 4.7 that in the past 15 years hit the area. Our interest is addressed to better understand the relationship between these events and the regional seismotectonic setting in terms of seismicity distribution and stress field. Two regions with different behavior in the seismic release can be distinguished: (i) along the watershed where seismicity is clustered at shallow depths (〈 15 km) and where strong earthquakes occurred in the past, (ii) an eastern portion where the seismicity is distributed across all of the crustal volume, locally reaching depths down to 30 km. The focal mechanism of the seismic sequences shows mainly normal fault kinematics coherent with the regional stress field. Detailed stress field analysis suggests a rotation of the principal stress axis moving from the axial part of the chain toward the Adriatic Sea to the east.
    Description: Published
    Description: 136-144
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: Northern Apennines ; Stress field ; Focal mechanisms ; Seismicity ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    Clues of Post-seismic Relaxation for the 1915 Fucino Earthquake (Central Italy) from Modeling of Leveling Data (2010)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: The 1915 Fucino earthquake (Ms=6.9) was one of the largest and most destructive events in Italy during the last century. The epicentral area is centered in the Abruzzi region (Central Italy), where a long historical record of large earthquakes is available. Seismotectonic studies on this region, based on instrumental seismicity (focal mechanism solutions of major events and stress analysis of background seismicity), borehole break-out studies and several geological and paleoseismological investigations, suggest NE-SW oriented active extension. The 1915 earthquake fault produced detectable surface ruptures for about 20 km along NW-SE striking SW-dipping structures. Coseismic geodetic data recorded in the epicentral area have been inverted in the past (Amoruso et al. 1998 and references therein), indicating a source fault dipping at moderate angle toward SW and a normal focal mechanism, with a non-negligible left-lateral component. Three high precision leveling lines located in a wide sector north and east of the Fucino plain were measured in 1950 and 1997-2000 by the IGM (Istituto Geografico Militare). Two consecutive lines run in a NW-SE direction along the chain, and form a "T-shape" net together with a third line SW-NE striking, towards the Adriatic sea. The total length is about 360 km with a mean benchmark density higher than 0.5 bm/km. The relative elevation changes recorded during this time interval show maximum values between 7 and 12 cm with a signal wavelength of 40-70 km. The observed elevation changes stand significantly above the calculated total error of 1.13 mm sqrt(L) km. A sharp gradient has been observed east of the earthquake epicenter, where we observe peculiar elevation changes along a 40 km long section of the leveling line. The observed elevation changes in Fucino earthquake area seem to comprise both regional tectonic deformation and post-seismic relaxation. The former and the latter effects are expected to dominate along sections of the leveling lines which are respectively about perpendicular and parallel to the Apennines. Since we compare measurements performed in 1950 and 1997-2000, relaxation effects refer to a late stage of the process. We have used Pollitz (1997) code for computing gravitational-viscoelastic postseismic relaxation on a layered spherical Earth. Different Earth models, characterized by different thicknesses and viscosities of crustal layers and of the upper mantle, have been considered. Even if S/N ratio of expected post-seismic effects is not high, comparison between predictions and observations allows to constrain regional crustal structure. Best-fit seismic moment is in good agreement with Amoruso et al. (1998) and residuals are fully consistent with expected regional tectonic deformation in central Apennines.
    Description: Published
    Description: San Francisco, USA
    Description: open
    Keywords: postseismic ; 1915 Fucino earthquake ; levelling ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 04. Solid Earth::04.06. Seismology::04.06.05. Historical seismology ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Magma dynamics of 2007 Stromboli effusive eruption as revealed by high precision location of seismic events. (2010)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Stromboli is considered one of the most active volcanoes in the world, and its persistent but moderate explosive activity is only interrupted by occasional episodes of more vigorous activity accompanied by lava flows. A new effusive eruption began in late February, 2007 and was characterised by intense seismic activity throughout the whole period. The accurate seismic signals analysis showed the presence of families of events with similar waveform signatures (i.e. multiplets) located beneath the crater region. Since traditional location techniques do not allow obtaining reliable hypocentres, our analysis focused on high precision locations of the seismicity, in order to better define the source geometry of the events. Hypocentres, therefore, have been relocated considering two steps: the first, based on a robust probabilistic approach, is used to find the absolute position of the clusters; the second exploits a master-event concept for the relative location of the events. Finally, the shape of the clusters and the temporal migration of the foci were correlated with the eruptive phases. The results show that the occurrence of a cluster of events is related to the opening and closure of a vent opened in the Sciara del Fuoco slope and, in particular, to the intrusion of a dike injected by central conduit in a radial direction, whereas another cluster lies in a narrow vertical volume positioned under the crater area. The geometry of the clusters suggests a source region depicting the shallower feeding system. Overall, the results highlight that the high precision locations method is an efficient and quick tool to obtain a better understanding of the magmatic processes occurring during an ongoing eruption.
    Description: Published
    Description: 405-415
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: eruption ; high precision location ; seismic swarms ; magma dynamics ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    A model for seismicity rates observed during the 1982–1984 unrest at Campi Flegrei caldera (Italy) (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: We consider the space–time distribution of seismicity during the 1982–1984 unrest at Campi Flegrei caldera (Italy) where a correlation between seismicity and rate of ground uplift was suggested. In order to investigate this effect, we present a model based on stress transfer from the deformation source responsible for the unrest to potential faults. We compute static stress changes caused by an inflating source in a layered half-space. Stress changes are evaluated on optimally oriented planes for shear failure, assuming a regional stress with horizontal extensional axis trending NNE-SSW. The inflating source is modeled as inferred by previous studies from inversion of geodetic data with the same crustal model here assumed. The magnitude of the regional stress is constrained by imposing an initial condition of “close to failure” to potential faults. The resulting spatial distribution of stress changes is in agreement with observations. We assume that the temporal evolution of ground displacement, observed by a tide-gauge at Pozzuoli, was due mainly to time dependent processes occurring at the inflating source. We approximate this time dependence in piecewise-linear way and we attribute it to each component of average stress-change in the region interested by the observed seismicity. Then we evaluate the effect of a time dependent stressing rate on seismicity, by following the approach indicated by Dieterich (1994) on the basis of the rate- and state-dependent rheology of faults. The seismicity rate history resulting from our model is in general agreement with data during the period 1982– 1984 for reasonable values of unconstrained model-parameters, the initial value of the direct effect of friction and the reference shear stressing rate. In particular, this application shows that a decreasing stressing-rate is effective in damping the seismicity rate.
    Description: Published
    Description: 287-298
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: Triggered seismicity ; Volcanic tremor ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
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  • 10
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    Societal need for improved understanding of climate change, anthropogenic impacts, and geo-hazard warning drive development of ocean observatories in European Seas (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Society’s needs for a network of in situ ocean observing systems cross many areas of earth and marine science. Here we review the science themes that benefit from data supplied from ocean observatories. Understanding from existing studies is fragmented to the extent that it lacks the coherent long-term monitoring needed to address questions at the scales essential to understand climate change and improve geo-hazard early warning. Data sets from the deep sea are particularly rare with long-term data available from only a few locations worldwide. These science areas have impacts on societal health and well-being and our awareness of ocean function in a shifting climate. Substantial efforts are underway to realise a network of open-ocean observatories around European Seas that will operate over multiple decades. Some systems are already collecting high-resolution data from surface, water column, seafloor, and sub-seafloor sensors linked to shore by satellite or cable connection in real or near-real time, along with samples and other data collected in a delayed mode. We expect that such observatories will contribute to answering major ocean science questions including: How can monitoring of factors such as seismic activity, pore fluid chemistry and pressure, and gas hydrate stability improve seismic, slope failure, and tsunami warning? What aspects of physical oceanography, biogeochemical cycling, and ecosystems will be most sensitive to climatic and anthropogenic change? What are natural versus anthropogenic changes? Most fundamentally, how are marine processes that occur at differing scales related? The development of ocean observatories provides a substantial opportunity for ocean science to evolve in Europe. Here we also describe some basic attributes of network design. Observatory networks provide the means to coordinate and integrate the collection of standardised data capable of bridging measurement scales across a dispersed area in European Seas adding needed certainty to estimates of future oceanic conditions. Observatory data can be analysed along with other data such as those from satellites, drifting floats, autonomous underwater vehicles, model analysis, and the known distribution and abundances of marine fauna in order to address some of the questions posed above. Standardised methods for information management are also becoming established to ensure better accessibility and traceability of these data sets and ultimately to increase their use for societal benefit. The connection of ocean observatory effort into larger frameworks including the Global Earth Observation System of Systems (GEOSS) and the Global Monitoring of Environment and Security (GMES) is integral to its success. It is in a greater integrated framework that the full potential of the component systems will be realised.
    Description: Published
    Description: 1-33
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: reserved
    Keywords: Seafloor and water columnobservatories ; 01. Atmosphere::01.01. Atmosphere::01.01.02. Climate ; 01. Atmosphere::01.01. Atmosphere::01.01.04. Processes and Dynamics ; 01. Atmosphere::01.01. Atmosphere::01.01.08. Instruments and techniques ; 03. Hydrosphere::03.01. General::03.01.03. Global climate models ; 03. Hydrosphere::03.01. General::03.01.07. Physical and biogeochemical interactions ; 03. Hydrosphere::03.01. General::03.01.08. Instruments and techniques ; 03. Hydrosphere::03.03. Physical::03.03.01. Air/water/earth interactions ; 03. Hydrosphere::03.03. Physical::03.03.02. General circulation ; 03. Hydrosphere::03.03. Physical::03.03.03. Interannual-to-decadal ocean variability ; 03. Hydrosphere::03.03. Physical::03.03.05. Instruments and techniques ; 03. Hydrosphere::03.04. Chemical and biological::03.04.01. Biogeochemical cycles ; 03. Hydrosphere::03.04. Chemical and biological::03.04.02. Carbon cycling ; 03. Hydrosphere::03.04. Chemical and biological::03.04.03. Chemistry of waters ; 03. Hydrosphere::03.04. Chemical and biological::03.04.04. Ecosystems ; 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases ; 03. Hydrosphere::03.04. Chemical and biological::03.04.06. Hydrothermal systems ; 03. Hydrosphere::03.04. Chemical and biological::03.04.08. Instruments and techniques ; 04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes ; 04. Solid Earth::04.04. Geology::04.04.04. Marine geology ; 04. Solid Earth::04.04. Geology::04.04.11. Instruments and techniques ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.05. Geomagnetism::04.05.05. Main geomagnetic field ; 04. Solid Earth::04.05. Geomagnetism::04.05.08. Instruments and techniques ; 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::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.03. Heat generation and transport ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism ; 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::05.01. Computational geophysics::05.01.01. Data processing ; 05. General::05.02. Data dissemination::05.02.99. General or miscellaneous ; 05. General::05.02. Data dissemination::05.02.01. Geochemical data ; 05. General::05.02. Data dissemination::05.02.02. Seismological data ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions ; 05. General::05.02. Data dissemination::05.02.04. Hydrogeological data ; 05. General::05.08. Risk::05.08.01. Environmental risk ; 05. General::05.08. Risk::05.08.02. Hydrogeological risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 11
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    Seismotectonic of Southern Apennines from recent passive seismic experiments (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: We used data of local earthquakes collected during two recent passive seismic experiments carried out in southern Italy in order to study the seismotectonic setting of the Lucanian Apennine and the surrounding areas. Based on continuous recordings of the temporary stations we extracted over 15,600 waveforms, which were hand-picked along with those recorded by the permanent stations of the Italian national seismic network obtaining a dense, high-quality dataset of P- and S-arrival times. We examined the seismicity occurring in the period 2001–2008 by relocating 566 out of 1047 recorded events with magnitudes ML ≥1.5 and computing 162 fault-plane solutions. Earthquakes were relocated using a minimum one-dimensional velocity model previously obtained for the region and a Vp/Vs ratio of 1.83. Background seismicity is concentrated within the upper crust (between 5 and 20km of depth) and it is mostly clustered along the Lucanian Apennine chain axis. A significant feature extracted from this study relates to the two E–W trending clusters located in the Potentino and in the Abriola–Pietrapertosa sector (central Lucania region). Hypocentral depths in both clusters are slightly deeper than those observed beneath the Lucanian Apennine. We suggest that these two seismic features are representative of the transition from the inner portion of the chain to the external margin characterized by dextral strike-slip kinematics. In the easternmost part of the study area, below the Bradano foredeep and the Apulia foreland, seismicity is generally deeper and more scattered. The sparse seismicity localized in the Sibari Plain, in the offshore area along the northeastern Calabrian coast and in the Taranto Gulf is also investigated thanks to the new recordings. This seismicity shows hypocenters between 12 and 20km of depth below the Sibari Plain and is deeper (foci between 10 and 35km of depth) in the offshore area of the Taranto Gulf. 102 well-constrained fault-plane solutions, showing predominantly normal and strike-slip character with tensional axes (T-axes) generally NE oriented, were selected for the stress tensor analysis. We investigated stress field orientation inverting focal mechanism belonging to the Lucanian Apennine and the Pollino Range, both areas characterized by a more concentrated background seismicity.
    Description: Published
    Description: 110-124
    Description: 3.2. Tettonica attiva
    Description: 5.7. Consulenze in favore di istituzioni nazionali e attività nell'ambito di trattati internazionali
    Description: JCR Journal
    Description: restricted
    Keywords: Background seismicity ; Passive seismic experiments ; Southern Apennines ; Apulia foreland ; Stress field ; Seismotectonic ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
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  • 12
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    Insights into explosive activity at closely-spaced eruptive vents using infrasound signals: Example of Mt. Etna 2008 eruption (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: On 13 May 2008 an eruptive fissure opened on Mount Etna's eastern flank feeding both explosive activity and lava effusion from multiple vents for about 14 months. During the investigated May-September 2008 eruptive period, infrasound recordings from a 4 station-sparse network allowed tracking of the explosive activity in terms of location and dynamics. In order to focus on activity from the eruptive fissure, the infrasonic events generated by the summit craters were selected by using both spectral features and time delays between pairs of stations and excluded from our analysis. Then, to accurately locate events from the fissure, we used a composite method, based on the semblance and brightness functions. This enabled the study of the co-existence of more than one infrasound source and/or its migration along the eruptive fissure. Hence, results permitted us to discriminate the number of active vents and their location along the fissure even when, due to poor weather conditions, it was not possible to access the vents or carry out direct observations. The eruptive activity was characterised by variations in the number of active vents according to the overall intensity of the eruptive event. Variability of the infrasound waveforms highlighted either that distinct vents produced signals with different waveforms, or that single vents generated different events during distinct periods of time, or finally both the previous phenomena. We applied the strombolian bubble vibration model to model waveform differences and attributed the signal variations to bubble radius changes.
    Description: Published
    Description: 1-11
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Etna ; Infrasound ; Infrasonic source location ; explosive activity ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 13
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    The geochemical signature caused by earthquake propagation in carbonate-hosted faults (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Friction laboratory experiments have been performed at sub-seismic (≈ 0.01 m/s) to seismic slip rates (N1 m/s) on dolomite gouges of the Triassic evaporites, which hosted the five mainshocks (5bMw b6) of the 1997 Colfiorito earthquakes in the Northern Apennines (Italy). Experimental faults are lubricated as marked falls of the steady state sliding friction coefficients, μss≈0.2, are observed at seismic slip rates, as opposed to values of μss≥0.6 attained for sub-seismic slip rates. At seismic slip rates decarbonation reactions, triggered by frictional heating in the experimental slip zone, produced: 1) new fluid (CO2) and mineral phases (e.g. Mg-calcite, periclase/brucite, lime/portlandite); 2) isotopic fractionation between the reaction products and the reactant mineral phases. The variations of total dissolved inorganic carbon (TIDC) in concentration Δ(TDIC) and isotopic composition Δ(δ13CTIDC) in a carbonate aquifer, with geochemical parameters similar to those of an aquifer located in the seismic belt of the Northern Apennines, have been modelled after an input of earthquake-produced CO2. Modelling results show that variation in Δ(δ13CTIDC) can be detected in volumes of groundwater which are about three times larger than those calculated for the variations in Δ(TDIC). For amounts of CO2 produced by coseismic decarbonation of ≤5 wt.% of the slip zone gouge, modelling results show that a detectable geochemical anomaly is obtained if the produced CO2 is dissolved into volumes of water comparable to those of the shallower aquifers feeding the springs in the 1997 Colfiorito earthquakes area. We conclude that the integration of results from laboratory experiments, performed at seismic condition, and geochemical analyses can potentially aid in the calibration of monitoring strategies of geochemical properties of water in seismically active areas and provide insights into seismic fault zone processes (e.g. constraints on the temperature rise during earthquake propagation).
    Description: Published
    Description: 225-232
    Description: 2.4. TTC - Laboratori di geochimica dei fluidi
    Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi
    Description: JCR Journal
    Description: reserved
    Keywords: earthquakes ; friction ; isotopes ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques
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  • 14
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    Splitting parameter yield (SPY): A program for semiautomatic analysis of shear wave splitting (2012)
    Elsevier
    Details
    Publication Date: 2017-04-03
    Description: SPY is a Matlab algorithm that analyzes seismic waveforms in a semiautomatic way, providing estimates of the two observables of the anisotropy: the shear-wave splitting parameters. We chose to exploit those computational processes that require less intervention by the user, gaining objectivity and reliability as a result. The algorithm joins the covariance matrix and the cross-correlation techniques, and all the computation steps are interspersed by several automatic checks intended to verify the reliability of the yields. The resulting semiautomation generates two new advantages in the field of anisotropy studies: handling a huge amount of data at the same time, and comparing different yields. From this perspective, SPY has been developed in the Matlab environment, which is widespread, versatile, and user-friendly. Our intention is to provide the scientific community with a new monitoring tool for tracking the temporal variations of the crustal stress field.
    Description: Published
    Description: 138-145
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: restricted
    Keywords: Crustal anisotropy ; Waveform analysis ; Seismic monitoring ; Stress field ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
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  • 15
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    Repeating volcano-tectonic earthquakes at Mt. Etna volcano (Sicily, Italy) during 1999–2009 (2013)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Repeating volcano-tectonic (VT) earthquakes, taking place at Mt. Etna during 1999–2009,were detected and analyzed to investigate their behavior. We found 735 families amounting to 2479 VT earthquakes, representing ~38% of all the analyzed VT earthquakes. The number of VT earthquakes making up the families ranges from 2 to 23. Over 70% of the families comprise 2 or 3 VT earthquakes and only 20 families by more than 10 events. The occurrence lifetime is also highly variable ranging from some minutes to ten years. In particular, more than half of the families have a lifetime shorter than 0.5 day and only ~10% longer than 1 year. On the basis of these results, most of the detected families were considered “burst-type”, i.e., show swarm-like occurrence, and hence their origin cannot be explained by a temporally constant tectonic loading. Indeed, since the analyzed earthquakes take place in a volcanic area, the rocks are affected not only by tectonic stresses related to the fairly steady regional stress field but also by local stresses, caused by the volcano, such as magma batch intrusions/ movements and gravitational loading.We focused on the five groups of families characterized by the longest repeatability over time, namely high number of events and long lifetime, located in the north-eastern, eastern and southern flanks of the volcano. Unlike the first four groups, which similarly to most of the detected families show swarm-like VT occurrences, group “v”, located in the north-eastern sector, exhibits a more “tectonic” behavior with the events making up such a group spread over almost the entire analyzed period. It is clear how both occurrence and slip rates do not remain constant but vary over time, and such changes are time-related to the occurrence of the 2002–2003 eruption. Finally, by FPFIT algorithm a good agreement between directions identified by nodal planes and the earthquake epicentral distribution was generally found.
    Description: Published
    Description: 1223 – 1236
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: restricted
    Keywords: repeating earthquakes ; Etna ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
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  • 16
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    Pattern recognition of volcanic tremor data on Mt. Etna (Italy) with KKAnalysis — A software program for unsupervised classification (2012)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Continuous seismic monitoring plays a key role in the surveillance of the Mt. Etna volcano. Besides earthquakes, which often herald eruptive episodes, the persistent background signal, known as volcanic tremor, provides important information on the volcano status. Changes in the regimes of activity are usually concurrent with variations in tremor characteristics. As continuous recording leads rapidly to the accumulation of large amounts of data, parameter extraction and automated processing become crucial. We propose techniques of unsupervised classification and present a software, named KKAnalysis, developed for this purpose. Essentials of KKAnalysis are demonstrated on tremor data recorded on Mt. Etna during various states of volcanic activity encountered in 2007 and 2008. KKAnalysis is based on MATLAB and combines various unsupervised pattern recognition techniques, in particular self-organizing maps (SOM) and cluster analysis. An early software version was successfully applied to seismic signals recorded on Mt. Etna during the eruption in 2001. Since each situation may require different configurations, we designed KKAnalysis with a specific GUI allowing users to easily modify parameters. All results are given graphically, in screen plots and metafiles (MATLAB and TIF format), as well as in alphanumeric form. The synoptic visualization of results from SOM and cluster analysis facilitates an immediate inspection. The potential of this representation is demonstrated by focusing on data recorded during a flank eruption on May 13, 2008. Changes of tremor characteristics can be clearly identified at a very early stage, well before enhanced volcanic activity becomes visible in the time series. At the same time, data reduction to less than 1% of the original amount is achieved, which facilitates interpretation and storage of the essential information. Running the program in a typical configuration requires computing time less than 1 min, allowing an on-line application for early warning purposes at INGV–Sezione di Catania
    Description: Published
    Description: 953-961
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 5.6. TTC - Attività di Sala Operativa
    Description: JCR Journal
    Description: reserved
    Keywords: Self-Organizing Map ; Cluster Analysis ; K-means ; Fuzzy C-means ; Volcano Seismology ; Volcano Monitoring ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.01. Computational geophysics::05.01.01. Data processing ; 05. General::05.01. Computational geophysics::05.01.02. Cellular automata, fuzzy logic, genetic alghoritms, neural networks ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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  • 17
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    Multiple resolution seismic attenuation imaging at Mt. Vesuvius (2010)
    Elsevier
    Details
    Publication Date: 2019-03-05
    Description: A three-dimensional S wave attenuation tomography of Mt. Vesuvius has been obtained with multiple measurements of coda-normalized S-wave spectra of local small magnitude earthquakes.We used 6609 waveforms, relative to 826 volcano-tectonic earthquakes, located close to the crater axis in a depth range between 1 and 4 km (below the sea level), recorded at seven 3-component digital seismic stations. We adopted a two-point ray-tracing; rays were traced in an high resolution 3-D velocity model. The spatial resolution achieved in the attenuation tomography is comparable with that of the velocity tomography (we resolve 300m side cubic cells). We statistically tested that the results are almost independent from the radiation pattern. We also applied an improvement of the ordinary spectral-slope method to both P- and S-waves, assuming that the differences between the theoretical and the experimental high frequency spectral-slope are only due to the attenuation effects. Consequently we could check the codanormalization method also comparing the S attenuation image with the P attenuation image. The images were obtained inverting the spectral data with a multiple resolution approach. Results have shown the general coincidence of low attenuation with high velocity zones. The joint interpretation of velocity and attenuation images allows us to interpret the low attenuation zone intruding toward the surface until a depth of 500m below the sea level as related to the residual part of solidified magma from the last eruption. In the depth range between −700 and −2300 images are consistent with the presence of multiple acquifer layers. No evidence of magma patches greater than the minimum cell dimension (300m) has been found. A shallow P wave attenuation anomaly (beneath the southern flank of the volcano) is consitent with the presence of gas saturated rocks. The zone characterized by the maximum seismic energy release cohincides with a high attenuation and low velocity volume, interpreted as a cracked medium.
    Description: Published
    Description: 17–32
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Attenuation tomography ; Mt. Vesuvius ; Coda normalization method ; Spectral slope ; Multi resolution inversion ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
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  • 18
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    An efficient mechanism to avert frictional melts during seismic ruptures (2010)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: We consider the spatio-temporal evolution of temperature due to frictional heating caused by the spontaneous propagation of 3-D dynamic seismic ruptures on planar faults. In our numerical experiments, which characterize typical crustal earthquakes, we assume that fault friction is controlled by different linear and nonlinear slip-dependent friction laws. In this paper we confirm that a necessary condition to prevent melting is to have a nearly complete breakdown stress drop. Our simulations, which employ a nonlinear slipdependent governing equation recently inferred from laboratory experiments by Sone and Shimamoto (2009), reproduce such a dramatic fault weakening and represent a plausible explanation for the prevention of melting during earthquake ruptures. We also demonstrate that low friction alone, although necessary, is not a sufficient condition to avert melts; the linear (or classical) slip-weakening (SW) law would produce melting, even assuming the same lengthscales and frictional levels. To avoid melting with linear SW law we have to impose a specific value of the SW distance. This reveals the prominent role of the time evolution of traction within the cohesive zone, where the stress release is realized, and of the value of the fracture energy density.
    Description: Published
    Description: 144-152
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: earthquake dynamics ; melting ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
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  • 19
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    Fault plane orientations of microearthquakes at Mt. Etna from theinversion of P-wave rise times (2010)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: A crucial point in the analysis of tectonic earthquakes occurring in a volcanic area is the inference of the orientation of the structures along which the ruptures occur. These structures represent zones of weakness which could favor the migration of melt toward the surface and the assessment of their geometry is a fundamental step toward efficient evaluation of volcanic risk. We analyzed a high-quality dataset of 171 lowmagnitude, tectonic earthquakes that occurred at Mt. Etna during the 2002–2003 eruption. We applied a recently developed technique aimed at inferring the source parameters (source size, dip and strike fault) and the intrinsic quality factor Qp of P waves from the inversion of rise times. The technique is based on numerically calibrated relationships among the rise time of first P waves and the source parameters for a circular crack rupturing at a constant velocity. For the most of the events the directivity source effect did not allow us to constrain the fault plane orientation. For a subset of 45 events with well constrained focal mechanisms we were able to constrain the “true” fault plane orientation. The level of resolution of the fault planes was assessed through a non linear analysis based on the random deviates technique. The significance of the retrieved fault plane solutions and the fit of the assumed source model to data were assessed through a χ-square test. Most of the retrieved fault plane solutions agree with the geometrical trend of known surface faults. The inferred source parameters and Qp are in agreement with the results of previous studies
    Description: Published
    Description: 247-256
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: rise time ; directivity ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
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  • 20
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    Spatio-temporal evolution of volcano seismicity: A laboratory study (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: We report a laboratory and microstructural study of a suite of deformation experiments in which basalt from Mount Etna volcano is deformed and fractured at an effective confining pressure representative of conditions under a volcanic edifice (40 MPa). Particular attention was paid to the formation of a fracture and damage zone with which to stimulate coupled hydro-mechanical interactions that create the various types of seismicity recorded on volcanic edifices, and which usually precede eruption. Location of AE events through time shows the formation of a fault plane during which waveforms exhibit the typical high frequency characteristics of volcano-tectonic (VT) earthquakes. We found that these VT earthquakes were particularly pronounced when generated using dry samples, compared to samples saturated with a pore fluid (water). VT events generated during deformation of water saturated sample are characterised by a distinctive high frequency onset and a longer, low frequency coda exhibiting properties often seen in the field as hybrid events. We present evidence that hybrid events are, in fact, the common type of volcanic seismic event with either VT or low frequency (LF) events representing end members, and whose proportion depend on pore fluid being present in the rock type being deformed, as well as how close the rock is to failure. We find a notable trend of reducing instances of hybrid events leading up to the failure stage in our experiments, suggesting that during this stage, the pore fluid present in the rock moves sufficiently quickly to provide a resonance, seen as a LF coda. Our data supports recent modeling and field studies that postulate that hybrid events generated in volcanic areas are likely to be generated through the interaction of hydrothermal fluids moving through a combination of pre-existing microcrack networks and larger faults, such as those we observe in forensic (post-test) examination.
    Description: Published
    Description: 315-323
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: reserved
    Keywords: volcano-tectonics, acoustic emission, rock physics, seismology, hazard ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.02. Data dissemination::05.02.02. Seismological data
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  • 21
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    Changes in the VLP seismic source during the 2007 Stromboli eruption (2010)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Aim of this paper is to identify variations in Very-Long-Period (VLP) source associated with eruptive style changes at Stromboli volcano (Italy) and to retrieve information about the shallow plumbing system that sustains the eruptive activity. We have considered a dataset of 74493 VLP events recorded during the period from January through August 2007, when an effusive eruption occurred (February 27–April 2).We performed a polarization analysis of the entire dataset and divided the considered period into four sub-periods on the basis of polarization characteristics. We then located the events and selected a subset of these events by applying a location quality threshold. The high quality locations demonstrate that during the effusive eruption the VLP sources first moved downward and then moved southwestward. To retrieve information about the geometry of the structures where the source processes take place, we further consider a subset of events and estimate their source mechanisms by using a moment tensor source function (MTSF) inversion technique. Inversion of the waveforms of the VLP events that occurred on February 27 allows us to obtain information about the dynamics of different source centroids distributed along different portions of the shallow magmatic conduits. The structure defined by the locations and source mechanisms shows a greater complexity compared with previous studies and their time variations give an insight into the kinematics of the eruption.
    Description: Published
    Description: 162–171
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: stromboli ; very-long-period events ; seismic source mechanism ; volcano seismology ; 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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