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  • Articles  (1,692,310)
  • American Institute of Physics  (610,459)
  • Wiley-Blackwell  (471,616)
  • Oxford University Press  (428,344)
  • National Academy of Sciences  (181,892)
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  • 1
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    Regional groundwater flow and interactions with deep fluids in western Apennine: the case of Narni-Amelia chain (Central Italy) (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2021-01-07
    Description: The elemental fluxes and heat flow associated with large aquifer systems can be significant both at local and at regional scales. In fact, large amounts of heat transported by regional groundwater flow can affect the subsurface thermal regime, and the amount of matter discharged towards the surface by large spring systems can be significant relative to the elemental fluxes of surface waters. The Narni-Amelia regional aquifer system (Central Italy) discharges more than 13 m3 sec)1 of groundwater characterised by a slight thermal anomaly, high salinity and high pCO2. During circulation in the regional aquifer, groundwater reacts with the host rocks (dolostones, limestones and evaporites) and mixes with deep CO2-rich fluids of mantle origin. These processes transfer large amounts of dissolved substances, in particular carbon dioxide, and a considerable amount of heat towards the surface. Because practically all the water circulating in the Narni-Amelia system is discharged by few large springs (Stifone-Montoro), the mass and energy balance of these springs can give a good estimation of the mass and heat transported from the entire system towards the surface. By means of a detailed mass and balance of the aquifer and considering the soil CO2 fluxes measured from the main gas emission of the region, we computed a total CO2 discharge of about 7.8 · 109 mol a)1 for the whole Narni-Amelia system. Finally, considering the enthalpy difference between infiltrating water and water discharged by the springs, we computed an advective heat transfer related to groundwater flow of 410 ± 50 MW.
    Description: Published
    Description: 182-196
    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: carbon dioxide degassing ; heat flow ; regional aquifer ; 04. Solid Earth::04.02. Exploration geophysics::04.02.01. Geochemical exploration ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 2
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    Retrospective short-term forecasting experiment in Italy based on the occurrence of strong (fore) shocks (2021)
    Oxford University Press
    Details
    Publication Date: 2021-03-15
    Description: In a recent work we computed the relative frequencies with which strong shocks (4.0≤Mw〈5.0), widely felt by the population were followed in the same area by potentially destructive main shocks (Mw≥5.0) in Italy. Assuming the stationarity of the seismic release properties, such frequencies can be tentatively used to estimate the probabilities of potentially destructive shocks after the occurrence of future strong shocks. This allows us to set up an alarm-based forecasting hypothesis related to strong foreshocks occurrence. Such hypothesis is tested retrospectively on the data of a homogenized seismic catalogue of the Italian area against a purely random hypothesis that simply forecasts the target main shocks proportionally to the space-time fraction occupied by the alarms. We compute the latter fraction in two ways a) as the ratio between the average time covered by the alarms in each area and the total duration of the forecasting experiment (60 years) and b) as the same ratio but weighted by the past frequency of occurrence of earthquakes in each area. In both cases the overall retrospective performance of our forecasting algorithm is definitely better than the random case. Considering an alarm duration of three months, the algorithm retrospectively forecasts more than 70% of all shocks with Mw5.5 occurred in Italy from 1960 to 2019 with a total space-time fraction covered by the alarms of the order of 2%. Considering the same space-time coverage, the algorithm is also able to retrospectively forecasts more than 40% of the first main shocks with Mw5.5 of the seismic sequences occurred in the same time interval. Given the good reliability of our results, the forecasting algorithm is set and ready to be tested also prospectively, in parallel to other ongoing procedures operating on the Italian territory.
    Description: This paper benefitted from funding provided by the European Union within the ambit of the H2020 project RISE (No. 821115), which in particular fully financed the PhD grant of one of the authors (E.B.).
    Description: Published
    Description: 1192–1206
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: JCR Journal
    Keywords: Earthquake interaction ; Statistical seismology ; forecasting, ; prediction ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
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    Lateglacial to Holocene trace element record (Ba, Mg, Sr) from Corchia Cave (Apuan Alps, central Italy): paleoenvironmental implications (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2021-06-16
    Description: In this study, Mg/Ca, Sr/Ca and Ba/Ca ratios in a Lateglacial to Holocene stalagmite (CC26) from Corchia Cave (central Italy) are compared with stable isotope data to define palaeohydrological changes. For most of the record, the trace element ratios show small absolute variability but similar patterns, which are also consistent with stable isotope variations. Higher trace element-to-calcium values are interpreted as responses to decreasing moisture, inducing changes in the residence time of percolation, producing prior calcite precipitation and/or variations in the hydrological routing. Statistically meaningful levels of covariability were determined using anomalies of Mg/Ca, d18O and d13C. Combining these three time series into a single ‘palaeomoisture-trend’ parameter, we highlight several events of reduced moisture (ca. 8.9–8.4, 6.2, 4.2, 3.1 and 2.0 ka), a humid period between ca. 7.9 and 8.3 ka and other shorter-term wet events at ca. 5.8, 5.3 and 3.7 ka. Most of these events can be correlated with climate changes inferred from other regional studies. For both extremities of the record (i.e. before ca. 12.4 ka and after ca. 0.5 ka) Mg/Ca and Sr/Ca are anti-correlated and show the greatest amplitude of values, a likely explanation for which involves aragonite and/or gypsum precipitation (the latter derived from pyrite oxidation) above the CC26 drip point.
    Description: Published
    Description: 381–392
    Description: 4A. Clima e Oceani
    Description: JCR Journal
    Description: restricted
    Keywords: central Italy; Corchia Cave; Holocene; speleothems; trace elements ; 01. Atmosphere::01.01. Atmosphere::01.01.02. Climate
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
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    So close, so different: geothermal flux shapes divergent soil microbial communities at neighbouring sites (2016)
    Wiley-Blackwell
    Details
    Publication Date: 2021-06-14
    Description: This study is focused on the (micro)biogeochemical features of two close geothermal sites (FAV1 and FAV2), both selected at the main exhalative area of Pantelleria Island, Italy. A previous biogeochemical survey revealed high CH4 consumption and the presence of a diverse community of methanotrophs at FAV2 site, whereas the close site FAV1 was apparently devoid of methanotrophs and recorded no CH4 consumption. Next-Generation Sequencing (NGS) techniques were applied to describe the bacterial and archaeal communities which have been linked to the physicochemical conditions and the geothermal sources of energy available at the two sites. Both sites are dominated by Bacteria and host a negligible component of ammonia-oxidizing Archaea (phylum Thaumarchaeota). The FAV2 bacterial community is characterized by an extraordinary diversity of methanotrophs, with 40% of the sequences assigned to Methylocaldum, Methylobacter (Gammaproteobacteria) and Bejerickia (Alphaproteobacteria); conversely, a community of thermo-acidophilic chemolithotrophs (Acidithiobacillus, Nitrosococcus) or putative chemolithotrophs (Ktedonobacter) dominates the FAV1 community, in the absence of methanotrophs. Since physical andchemical factors of FAV1, such as temperature and pH, cannot be considered limiting for methanotrophy, it is hypothesized that the main limiting factor for methanotrophs could be high NH4+ concentration. At the same time, abundant availability of NH4+ and other high energy electron donors and acceptors determined by the hydrothermal flux in this site create more energetically favourable conditions for chemolithotrophs that outcompete methanotrophs in non-nitrogen-limited soils.
    Description: Published
    Description: 150–162
    Description: 4V. Vulcani e ambiente
    Description: JCR Journal
    Description: restricted
    Keywords: geothermal soils ; geomicrobiology ; chemolithotrophs ; methanotrophs ; Pantelleria ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
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    Thermal structure of a vanishing subduction system. An example of seismically-derived crustal temperature along the Italian peninsula (2020)
    Oxford University Press
    Details
    Publication Date: 2020-10-16
    Description: This article has been accepted for publication in Geophysical Journal International ©: The Authors 2019. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.
    Description: The active tectonic processes in convergent margins confer a high degree of complexity to the crust. Determining the thermal structure is, therefore, key to better elucidate the nature of those processes. In order to reconstruct the thermal structure of the crust beneath the Italian peninsula, we combine the most recent and accurate shear-wave velocity model that is currently available with thermodynamic modelling, assuming a global average crustal composition with no lateral variations. Our model, presented in terms of Moho temperature and crustal thermal gradients, shows a very good agreement with the known thermal anomalies associated with the backarc spreading related to the Apennine subduction. Importantly, we envisage a new anomalous region of high Moho temperatures in NW Italy (T 〉 800 degrees C at 30 km), at the transition between the Alps and Apennine orogens. The lowest temperatures of our model, corresponding to geothermal gradients 〈 19 degrees C km(-1), are obtained in the still active but slow-convergent portion of the northern Apennine. Moho temperatures increase moving southwards along the Apennine chain, an observation that is coherent with the evidence of ceasing subduction and consequent rebalancing of the depressed isotherms along the slab. Our results suggest that a thermal structure in different tectonic settings can be inferred with acceptable uncertainties based on absolute seismic velocity models. In this sense, our approach can be extended to any other region.
    Description: Published
    Description: 239–247
    Description: 1T. Struttura della Terra
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    Magma andVolatile Supply to Post-collapse Volcanism and Block Resurgence in Siwi Caldera (Tanna Island,Vanuatu Arc) (2011)
    Oxford University Press
    Details
    Publication Date: 2020-11-20
    Description: Siwi caldera, in the Vanuatu arc (Tanna island), is a rare volcanic complex where both persistent eruptive activity (Yasur volcano)and rapid block resurgence (Yenkahe horst) can be investigated simultaneously during a post-caldera stage. Here we provide new constraints on the feeding system of this volcanic complex, based on a detailed study of the petrology, geochemistry and volatile content of Yasur^Siwi bulk-rocks and melt inclusions, combined with measurements of the chemical composition and mass fluxes of Yasur volcanic gases. Major and trace element analyses of Yasur^ Siwi volcanic rocks, together with literature data for other volcanic centers, point to a single magmatic series and possibly long-lived feeding of Tanna volcanism by a homogeneous arc basalt. Olivine-hosted melt inclusions show that the parental basaltic magma, which produces basaltic-trachyandesites to trachyandesites by 50^70% crystal fractionation, is moderately enriched in volatiles ( 1wt % H2O, 0·1wt % S and 0·055 wt % Cl). The basaltic-trachyandesite magma, emplaced at between 4^5 km depth and the surface, preserves a high temperature (1107 158C) and constant H2O content ( 1wt %) until very shallow depths, where it degasses extensively and crystallizes. These conditions, maintained over the past 1400 years of Yasur activity, require early water loss during basalt differentiation, prevalent open-system degassing, and a relatively high heat flow ( 109W). Yasur volcano releases on average 13·4 103 tons d 1 of H2O and 680 tons d 1 of SO2, but moderate amounts of CO2 (840 tons d 1), HCl (165 tons d 1), and HF (23 tons d 1). Combined with melt inclusion data, these gas outputs constrain a bulk magma degassing rate of 5 107 m3 a 1, about a half of which is due to degassing of the basaltic-trachyandesite. We compute that 25 km3 of this magma have degassed without erupting and have accumulated beneath Siwi caldera over the past 1000 years, which is one order of magnitude larger than the accumulated volume uplift of the Yenkahe resurgent block. Hence, basalt supply and gradual storage of unerupted degassed basaltictrachyandesite could easily account for (or contribute to) the Yenkahe block resurgence.
    Description: Published
    Description: 1077-1105
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: 2.4. TTC - Laboratori di geochimica dei fluidi
    Description: JCR Journal
    Description: restricted
    Keywords: Vanuatu arc ; Yasur ; gas fluxes ; volatiles ; melt inclusions ; resurgent block ; volcano thermal budget ; 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::04.08.03. Magmas
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  • 7
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    An Intercomparison of Precipitable Water Vapor Measurements Obtained During the ECOWAR Field Campaign (2009)
    American Institute of Physics
    Details
    Publication Date: 2020-12-14
    Description: In this study we present an intercomparison of measurements of very low water vapor column content obtained with a Ground-Based Millimeter-wave Spectrometer (GBMS), Vaisala RS92k radiosondes, a Raman Lidar, and an IR Fourier Transform Spectrometer. These sets of measurements were carried out during the primary field campaign of the ECOWAR (Earth COoling by WAter vapor Radiation) project which took place on the Western Italian Alps from 3 to 16 March, 2007.
    Description: Published
    Description: 135-138
    Description: 1.8. Osservazioni di geofisica ambientale
    Description: N/A or not JCR
    Description: open
    Keywords: Precipitable Water Vapor ; ECOWAR ; IR and Millimeter-Wave Spectroscopy ; 01. Atmosphere::01.01. Atmosphere::01.01.01. Composition and Structure ; 01. Atmosphere::01.01. Atmosphere::01.01.02. Climate
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Geological and geophysical investigation of Kamil crater, Egypt (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2020-12-21
    Description: We detail the Kamil crater (Egypt) structure and refine the impact scenario, based on the geological and geophysical data collected during our first expedition in February 2010. Kamil Crater is a model for terrestrial small-scale hypervelocity impact craters. It is an exceptionally well-preserved, simple crater with a diameter of 45 m, depth of 10 m, and rayed pattern of bright ejecta. It occurs in a simple geological context: flat, rocky desert surface, and target rocks comprising subhorizontally layered sandstones. The high depth-to-diameter ratio of the transient crater, its concave, yet asymmetric, bottom, and the fact that Kamil Crater is not part of a crater field confirm that it formed by the impact of a single iron mass (or a tight cluster of fragments) that fragmented upon hypervelocity impact with the ground. The circular crater shape and asymmetries in ejecta and shrapnel distributions coherently indicate a direction of incidence from the NW and an impact angle of approximately 30 to 45 . Newly identified asymmetries, including the off-center bottom of the transient crater floor downrange, maximum overturning of target rocks along the impact direction, and lower crater rim elevation downrange, may be diagnostic of oblique impacts in well-preserved craters. Geomagnetic data reveal no buried individual impactor masses 〉100 kg and suggest that the total mass of the buried shrapnel 〉100 g is approximately 1050–1700 kg. Based on this mass value plus that of shrapnel 〉10 g identified earlier on the surface during systematic search, the new estimate of the minimum projectile mass is approximately 5 t.
    Description: Published
    Description: 1842–1868
    Description: 3.8. Geofisica per l'ambiente
    Description: JCR Journal
    Description: restricted
    Keywords: Impact craters ; geophysical survey ; iron meteorite ; impact scenario ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous ; 04. Solid Earth::04.02. Exploration geophysics::04.02.07. Instruments and techniques ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    Revised Chronology of the Sulmona Lacustrine Succession, Central Italy (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2020-12-07
    Description: We present new stratigraphic, palaeomagnetic, 87Sr/86Sr and 40Ar/39Ar data from a lacustrine succession of the Sulmona basin, central Italy, which, according to an early study, included six unconformitybounded lacustrine units (from SUL6, oldest, to SUL1, youngest) spanning the interval 〉600 to 2 ka. The results of the present study, on the one hand confirm some of the previous conclusions, but by contrast reveal that units SUL2 and SUL1, previously attributed to the Holocene, are actually equivalent to the older SUL6 and SUL5 units – here dated to 814–〉530 ka and 530–〈457 ka, respectively – and that the U-series dates previously published for both former SUL2 and SUL1 units yielded abnormally young ages. In light of the present results, a reassessment of the chronology of the Sulmona basin succession and a revision of the tephrostratigraphy of the SUL2/SUL6 and SUL1/SUL5 units is in order.
    Description: Published
    Description: 545–551
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: 40Ar/39Ar dating; central Italy ; Sr isotope composition ; Sulmona lacustrine succession ; Brunhes–Matuyama geomagnetic reversal ; tephrostratigraphy ; U-series dating ; 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::04.05.06. Paleomagnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
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    Aseismic transient driving the swarm-like seismic sequence in the Pollino range, Southern Italy (2020)
    Oxford University Press
    Details
    Publication Date: 2020-12-15
    Description: This article has been accepted for publication in Geophysical Journal International ©: The Authors 2015. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.
    Description: ectonic earthquake swarms challenge our understanding of earthquake processes since it is difficult to link observations to the underlying physical mechanisms and to assess the hazard they pose. Transient forcing is thought to initiate and drive the spatio-temporal release of energy during swarms. The nature of the transient forcing may vary across sequences and range from aseismic creeping or transient slip to diffusion of pore pressure pulses to fluid redistribution and migration within the seismogenic crust. Distinguishing between such forcing mechanisms may be critical to reduce epistemic uncertainties in the assessment of hazard due to seismic swarms, because it can provide information on the frequency–magnitude distribution of the earthquakes (often deviating from the assumed Gutenberg–Richter relation) and on the expected source parameters influencing the ground motion (for example the stress drop). Here we study the ongoing Pollino range (Southern Italy) seismic swarm, a long-lasting seismic sequence with more than five thousand events recorded and located since October 2010. The two largest shocks (magnitude M w = 4.2 and M w = 5.1) are among the largest earthquakes ever recorded in an area which represents a seismic gap in the Italian historical earthquake catalogue. We investigate the geometrical, mechanical and statistical characteristics of the largest earthquakes and of the entire swarm. We calculate the focal mechanisms of the M l 〉 3 events in the sequence and the transfer of Coulomb stress on nearby known faults and analyse the statistics of the earthquake catalogue. We find that only 25 per cent of the earthquakes in the sequence can be explained as aftershocks, and the remaining 75 per cent may be attributed to a transient forcing. The b-values change in time throughout the sequence, with low b-values correlated with the period of highest rate of activity and with the occurrence of the largest shock. In the light of recent studies on the palaeoseismic and historical activity in the Pollino area, we identify two scenarios consistent with the observations and our analysis: This and past seismic swarms may have been ‘passive’ features, with small fault patches failing on largely locked faults, or may have been accompanied by an ‘active’, largely aseismic, release of a large portion of the accumulated tectonic strain. Those scenarios have very different implications for the seismic hazard of the area.
    Description: Published
    Description: 1553–1567
    Description: 4T. Sismicità dell'Italia
    Description: JCR Journal
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  • 11
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    Non-stability of the noise HVSR at sites near or on topographic heights (2021)
    Oxford University Press
    Details
    Publication Date: 2021-01-18
    Description: The horizontal to vertical spectral ratio (HVSR) of seismic noise is often used to investigate site effects, and it is usually assumed to be a stable feature of the site considered. Here we show that such an assumption is not always justified, and may lead to incorrect conclusions. The HVSR analysis was performed on ambient seismic noise recordings lasting from weeks to months at many sites in Calabria, Italy. Results show a variety of site effects, from the resonance of a shallow sedimentary layer to the polarized amplification of horizontal ground motion associated with topographic effects. We describe the results of seven sites whose HVSR is characterized by dual content: one that is persistent, and another appearing only occasionally. Two sites very near the coast of the Tyrrhenian sea and five sites in the Calabrian Arc mountains show the most remarkable results. The shape of the HVSR changes significantly at these sites when the amplitude of background noise increases in a broad frequency band during periods of bad weather. The occasional contribution to the HVSR consists of one or more peaks, depending on the site, that appear only when the amplitude of ambient noise is higher than usual. The seven sites where we observe the HVSR variability are all located in complex geological environments, on mountains, ridges or foothills. A variation of the HVSR correlated with the day–night cycle is also observed at some of these sites.
    Description: Published
    Description: 2162–2171
    Description: 1T. Struttura della Terra
    Description: JCR Journal
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  • 12
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    The Shallow Plumbing System of Piton de la Fournaise Volcano (La Reunion Island, Indian Ocean) Revealed by the Major 2007 Caldera-Forming Eruption (2021)
    Oxford University Press
    Details
    Publication Date: 2021-02-10
    Description: The 2007 caldera-forming eruption of Piton de la Fournaise (PdF) erupted the largest volume of magma (210 Mm3)recorded at this volcano in at least three centuries. Major and trace element and Sr^Nd isotope data for bulk-rocks, groundmasses and olivine phenocrysts have been combined with melt inclusion data (major, trace and volatile elements) to track magma evolution over the whole eruptive sequence. We show that each eruptive phase had a distinctive geochemical and petrological signature and that caldera collapse on 5 April was preceded by a marked shift in bulk magma composition and crystal content and size. Aphyric basalt erupted at the beginning of the sequence (February 2007) had relatively high Sr isotope ratio (87Sr/86Sr ¼ 0·70420^0·704180) and low Nd isotopic ratio(143Nd/144Nd ¼ 0·51285^0·51286). Olivine-basalts extruded on2^5 April just before caldera collapse are less enriched in radiogenic Sr (87Sr/86Sr ¼ 0·70412^0·70416), but characterized by the same Nd isotopic composition. This magma is interpreted as a new deep input, which pressurized the shallow PdF plumbing system and triggered the 2007 activity. Post-collapse oceanite lavas represent the main volume of magma extruded in 2007. Their bulk-rocks and groundmasses have 87Sr/86Sr (0·70418) intermediate between those of February and 5 April, and similar to those of the March 2007 and 2001^2006 lavas.We show that the Steady State Basalts (SSB) commonly erupted at PdF are hybrid melts, which result from multistep mixing between ‘alkaline’and ‘transitional’end-members. Our results lead us to propose a new model of the PdF plumbing system to reconcile the petrological, geochemical and geophysical observations: (1) the shallow portion (above sea level) of the PdF plumbing system hosts several small sills, in which magma experiences variable degrees of degassing, cooling and crystallization; (2) oceanite lavas result from the withdrawal of shallow harrisitic mushes stored at low pressures (548 MPa; 51800^2400 m depth) below both the volcano summit and its eastern flank; (3) water degassing plays a major role in fast magma crystallization at shallow depths. Multistep ascent and periodic extrusion of the shallow magmas is promoted by injections of deeper and hotter basaltic magma, containing up to 1·3 wt % H2O and 1630 ppm S. In 2007, the new deep input was the ultimate source of the large excess in sulfur degassing detected by satellites. Lateral draining and intrusion of magma below the eastern flank of the volcano are the cause of major volcano deformation, flank sliding and summit caldera collapse.
    Description: Published
    Description: 1287-1315
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Description: 4V. Processi pre-eruttivi
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Keywords: Piton de la Fournaise ; plumbing system ; magma reservoir ; caldera collapse ; melt inclusions ; volatile budget ; isotope geochemistry ; basalt
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 13
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    Numerical analysis of interseismic, coseismic and postseismic phases for normal and reverse faulting earthquakes in Italy (2021)
    Oxford University Press
    Details
    Publication Date: 2021-02-23
    Description: The preparation, initiation, and occurrence dynamics of earthquakes in Italy are governed by several frequently unknown physical mechanisms and parameters. Understanding these mechanisms is crucial for developing new techniques and approaches for earthquake monitoring and hazard assessments. Here, we develop a first-order numerical model simulating quasi-static crustal interseismic loading, coseismic brittle episodic dislocations, and postseismic relaxation for extensional and compressional earthquakes in Italy based on a common framework of lithostatic and tectonic forces. Our model includes an upper crust, where the fault is locked, and a deep crust, where the fault experiences steady shear.
    Description: Published
    Description: 627–645
    Description: 2T. Deformazione crostale attiva
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 14
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    An automatically generated high-resolution earthquake catalogue for the 2016–2017 Central Italy seismic sequence, including P and S phase arrival times (2021)
    Oxford University Press
    Details
    Publication Date: 2021-03-24
    Description: The 2016–17 central Italy earthquake sequence began with the first mainshock near the town of Amatrice on August 24 (MW 6.0), and was followed by two subsequent large events near Visso on October 26 (MW 5.9) and Norcia on October 30 (MW 6.5), plus a cluster of 4 events with MW 〉 5.0 within few hours on January 18, 2017. The affected area had been monitored before the sequence started by the permanent Italian National Seismic Network (RSNC), and was enhanced during the sequence by temporary stations deployed by the National Institute of Geophysics and Volcanology and the British Geological Survey. By the middle of September, there was a dense network of 155 stations, with a mean separation in the epicentral area of 6–10 km, comparable to the most likely earthquake depth range in the region. This network configuration was kept stable for an entire year, producing 2.5 TB of continuous waveform recordings. Here we describe how this data was used to develop a large and comprehensive earthquake catalogue using the Complete Automatic Seismic Processor (CASP) procedure. This procedure detected more than 450,000 events in the year following the first mainshock, and determined their phase arrival times through an advanced picker engine (RSNI-Picker2), producing a set of about 7 million P- and 10 million S-wave arrival times. These were then used to locate the events using a non-linear location (NLL) algorithm, a 1D velocity model calibrated for the area, and station corrections and then to compute their local magnitudes (ML). The procedure was validated by comparison of the derived data for phase picks and earthquake parameters with a handpicked reference catalogue (hereinafter referred to as ‘RefCat’). The automated procedure takes less than 12 hours on an Intel Core-i7 workstation to analyse the primary waveform data and to detect and locate 3000 events on the most seismically active day of the sequence. This proves the concept that the CASP algorithm can provide effectively real-time data for input into daily operational earthquake forecasts, The results show that there have been significant improvements compared to RefCat obtained in the same period using manual phase picks. The number of detected and located events is higher (from 84,401 to 450,000), the magnitude of completeness is lower (from ML 1.4 to 0.6), and also the number of phase picks is greater with an average number of 72 picked arrival for a ML = 1.4 compared with 30 phases for RefCat using manual phase picking. These propagate into formal uncertainties of ± 0.9km in epicentral location and ± 1.5km in depth for the enhanced catalogue for the vast majority of the events. Together, these provide a significant improvement in the resolution of fine structures such as local planar structures and clusters, in particular the identification of shallow events occurring in parts of the crust previously thought to be inactive. The lower completeness magnitude provides a rich data set for development and testing of analysis techniques of seismic sequences evolution, including real-time, operational monitoring of b-value, time-dependent hazard evaluation and aftershock forecasting.
    Description: Published
    Description: 555–571
    Description: 3T. Fisica dei terremoti e Sorgente Sismica
    Description: JCR Journal
    Keywords: 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 15
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    Erratum: On seismic ambient noise cross-correlation and surface-wave attenuation (2021)
    Oxford University Press
    Details
    Publication Date: 2021-05-12
    Description: erratum paper
    Description: Published
    Description: 1090-1092
    Description: 1T. Struttura della Terra
    Description: JCR Journal
    Keywords: Theoretical seismology ; Seismic attenuation ; Seismic noise ; Surface waves ; Free oscillations ; Seismic interferometry ; 04.06. Seismology ; 04.01. Earth Interior
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 16
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    Crustal structure of the Azores Archipelago from Rayleigh wave ellipticity data (2021)
    Oxford University Press
    Details
    Publication Date: 2021-05-12
    Description: This article has been accepted for publication inGeophysical Journal International ©The Author(s) 2020. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
    Description: Determining the crustal structure of ocean island volcanoes is important to understand the formation and tectonic evolution of the oceanic lithosphere and tectonic swells in marine settings, and to assess seismic hazard in the islands. The Azores Archipelago is located near a triple junction system and is possibly under the influence of a mantle plume, being at the locus of a wide range of geodynamic processes. However, its crustal structure is still poorly constrained and debated due to the limited seismic coverage of the region and the peculiar linear geometry of the islands. To address these limitations, in this study we invert teleseismic Rayleigh wave ellipticity measurements for 1-D shear wave speed (VS) crustal models of the Azores Archipelago. Moreover, we test the reliability of these new models by using them in independent moment tensor inversions of local seismic data and demonstrate that our models improve the waveform fit compared to previous models. We find that data from the westernmost seismic stations used in this study require a shallower Moho depth (∼10 km) than data from stations in the eastern part of the archipelago (∼13–16 km). This apparent increase in the Moho depth with increasing distance from the mid-Atlantic ridge (MAR) is expected. However, the rate at which Moho deepens away from the MAR is greater than that predicted from a half-space cooling model, suggesting that local tectonic perturbations have modified crustal structure. The 1-D VS models obtained beneath the westernmost seismic stations also show higher wave speeds than for the easternmost stations, which correlates well with the ages of the islands except Santa Maria Island. We interpret the relatively low VS profile found beneath Santa Maria Island as resulting from underplating, which agrees with previous geological studies of the island. Compared to a recent receiver function study of the region, the shallow structure (top ∼2 km) in our models shows lower shear wave speed, which may have important implications for future hazard studies of the region. More generally, the new seismic crustal models we present in this study will be useful to better understand the tectonics, seismicity, moment tensors and strong ground motions in the region.
    Description: Published
    Description: 1232–1247
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 17
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    Changing modes and rates of mafic magma supply at Pantelleria (Sicily Channel, Southern Italy): new perspectives on the volcano factory drawn upon olivine records (2021)
    Oxford University Press
    Details
    Publication Date: 2021-05-12
    Description: The island of Pantelleria, located in the Sicily Channel Rift Zone (Italy), has been the site of violent peralkaline silicic magmatism alternating with minor effusive to low-intensity Strombolian erup- tions of basaltic composition. The basaltic rock suites exposed on the island were sampled to in- vestigate the plumbing system dynamics through the study of chemical stratigraphy and temporal records of olivine crystals. Our petrographic and geochemical observations, together with the com- positional variability of olivine, suggest different evolutionary histories for basaltic magmas erupted over two major periods divided by the 􏰃45 ka Green Tuff (GT) eruption. Core-to-rim com- positional traverses across olivine crystals document different types of zoning. We recognized oliv- ine zones affected by Fo oscillations at very fine scales in the inner cores, rims and/or in intermedi- ate portions of crystals and used them to reconstruct the residence and passage of crystals through different magmatic environments, with P–T–ƒO2 and compositional characteristics con- strained by thermodynamic modeling. The sequence of magmatic environments evidenced by oliv- ine zoning indicate that the pre-GT volcanic period was dominated by injection at shallow crustal levels (􏰃300–200 MPa) of primitive melts, initially moving from a deep storage zone at the crust- mantle boundary. Supply of this magma significantly decreased after the GT eruption, while the dy- namics of magma transfer within the upper portion of the plumbing system were greatly enhanced. The diffusive relaxation of olivine zoning provided the timing of storage and migration of a crystal through different environments. For magmas feeding the ancient (〉45 ka) basaltic activ- ity we retrieved transfer histories that are much longer (up to 􏰃3 years) if compared with those cal- culated for the post-GT basalts (1–9 months). The compositional and temporal dataset presented in this study supports the idea that the GT eruption and the subsequent collapse of the volcanic edi- fice could have caused major changes to the internal structural setting of Pantelleria, creating more favorable conditions for the migration of magmas in the upper portions of the plumbing system.
    Description: Published
    Description: egaa05
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: JCR Journal
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  • 18
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    The Deep Plumbing System of Ischia: a Physico-chemical Window on the Fluid-saturated and CO2-sustained Neapolitan Volcanism (Southern Italy) (2021)
    Oxford University Press
    Details
    Publication Date: 2021-05-12
    Description: Ischia, a volcanic island located 18 miles SW of Naples (Southern Italy), is a densely populated active caldera that last erupted in AD 1302. Melt inclusions in phenocrysts of the Vateliero and Cava Nocelle shoshonite^latite eruptive products (6th to 4th centuries BC) constrain the structure and nature of the Ischia deep magmatic feeding system.Their geochemical characteristics make Ischia a natural borehole for probing the physico-chemical conditions of magma generation in mantle contaminated by slab-derived fluids or melts, largely dominated by CO2.Volatile concentrations in olivine-hosted melt inclusions require gas^melt equilibria at between 3 and 18 km depth. In agreement with what has already been demonstrated at the other neighboring Neapolitan volcanoes (Procida, Campi Flegrei caldera and Somma^Vesuvius volcanic complex), a major crystallization depth at 8^10 km has been identified.The analyzed melt inclusions provide clear evidence for CO2-dominated gas fluxing and consequent dehydration of magma batches stagnating at crustal discontinuities. Gas fluxing is further supported by selective enrichment in K owing to fluid-transfer during magma differentiation.This takes place under oxidized conditions (Fe3þ /Fe 0·3) that can be fixed by an equimolar proportion of divalent and trivalent iron in the melt if post-entrapment crystallization of the host olivine is discarded.The melt inclusion data, together with data from the literature for other Neapolitan volcanoes, show that magmatism and volcanism in the Neapolitan area, despite differences in composition and eruption dynamics, are closely linked to supercritical CO2-rich fluids. These fluids are produced by devolatilization of subducting terrigenous^pelagic metasediments and infiltrate the overlying mantle wedge, generate magmas and control their ascent up to eruption. Geochemical characteristics of Ischia and the other Neapolitan volcanoes reveal that the extent of fluid or melt contamination of the pre-subduction asthenospheric mantle wedge was similar among these volcanoes. However, differences in the isotopic compositions of the erupted magmas (more enriched in radiogenic Sr at Ischia, Campi Flegrei and Somma^Vesuvius with respect to Procida) and the amount of H2O in the plumbing system of these volcanoes (almost double at Ischia, Campi Flegrei and Somma^Vesuvius than at Procida) reflect the different flow-rates of deep slab-derived fluids or melts through the mantle wedge, which, in turn, control the amount of generated magma.The high bulk permeability of the lithosphere below Ischia, Campi Flegrei and Somma^Vesuvius, determined by the occurrence of intersecting NW^SE and NE^SW regional fault systems, favours fluid ascent and accumulation at crustal levels, with consequent larger magma production and storage than at Procida, located along the NE^SW system.
    Description: Published
    Description: 951-984
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Description: 4V. Processi pre-eruttivi
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Keywords: CO2-fluxing ; melt inclusions ; redox state ; trachybasalts
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 19
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    Empirical H/V spectral ratios estimated in two deep sedimentary basins using microseisms recorded by short-period seismometers (2009)
    Wiley-Blackwell
    Details
    Publication Date: 2021-06-22
    Description: In this work, we analyse continuous measurements of microseisms to assess the reliability of the fundamental resonance frequency estimated by means of the horizontal-to-vertical (H/V) spectral ratio within the 0.1–1 Hz frequency range, using short-period sensors (natural period of 1 s). We apply the H/V technique to recordings of stations installed in two alluvial basins with different sedimentary cover thicknesses—the Lower Rhine Embayment (Germany) and the Gubbio Plain (Central Italy). The spectral ratios are estimated over the time–frequency domain, and we discuss the reliability of the results considering both the variability of the microseism activity and the amplitude of the instrumental noise. We show that microseisms measured by short period sensors allow the retrieval of fundamental resonance frequencies greater than about 0.1–0.2 Hz, with this lower frequency bound depending on the relative amplitude of themicroseism signal and the self-noise of the instruments. In particular,we show an examplewhere the considered short-period sensor is connected to instruments characterized by an instrumental noise level which allows detecting only fundamental frequencies greater than about 0.4 Hz. Since the frequency at which the peak of the H/V spectral ratio is biased depends upon the seismic signal-to-instrument noise ratio, the power spectral amplitude of instrumental self-noise should be always considered when interpreting the frequency of the peak as the fundamental resonance frequency of the investigated site.
    Description: Published
    Description: 175-184
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: open
    Keywords: site effects ; fourier analysis ; 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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  • 20
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    Sulphur behaviour and redox conditions in etnean magmas during magma differentiation and degassing (2021)
    Oxford University Press
    Details
    Publication Date: 2021-06-21
    Description: Sulphur behaviour and variations in redox conditions during magma differentiation and degassing in the Mt Etna (Italy) volcanic system have been explored by integrating the study of olivine-hosted melt inclusions (MIs) with an experimental survey of sulphur solubility in hydrous basaltic magmas. Sulphur solubility experiments were performed at conditions relevant to the Etnean plumbing system (1200 C, 200MPa and oxygen fugacity between NNOþ0 2 and NNOþ1 7, with NNO being the nickel–nickel oxide buffer), and their results confirm the important control of oxygen fugacity (fO2) on S abundance in mafic magmas and on S partitioning between fluid and melt phases (DSfluid/melt). The observed DSfluid/melt value increases from 5164 to 14666 when fO2 decreases from NNOþ1 760 5 to NNOþ0 3. Based on the calculated DSfluid/melt and a careful selection of previously published data, an empirical model is proposed for basaltic magmas to predict the variation of DSfluid/melt values with variations in P (25–300 MPa), T (1030–1200 C) and fO2 (between NNO– 0 8 and NNOþ2 4). Olivine-hosted melt inclusions (Fo89-91) from tephra of the prehistoric (4 ka BP) sub-plinian picritic eruption, named FS (‘Fall Stratified’), have been investigated for their major element compositions, volatile contents and iron speciation (expressed as Fe3þ/PFe ratio). These primitive MIs present S content from 235677 to 34456168 ppm, and oxygen fugacity values, estimated from Fe3þ/PFe ratios, range from NNOþ0 760 2 to NNOþ1 660 2. Iron speciation has also been investigated in more evolved and volatile-poorer Etnean MIs. The only primitive melt inclusion from the Mt Spagnolo eruption (4–15 ka BP) presents a S content of 1515649ppm and an estimated fO2 of NNOþ1 460 1. The more evolved MIs (from 2002–2003, 2006, 2008–2009 and 2013 eruptions) have S content lower than 500 ppm, and their Fe3þ/RFe ratios result in fO2 between NNO– 0 960 1 and NNOþ0 460 1. Redox conditions and S behaviour in Etnean magmas during degassing and fractional crystallization were modelled coupling MELTS code with our empirical DSfluid/melt model. Starting from an FS-type magma composition and upon decrease of T and P, fractional crystallization of olivine, clinopyroxene, spinel and plagioclase causes a significant fO2 decrease. The fO2 reduction, in turn, causes a decrease in sulphur solubility and an increase in DSfluid/melt, promoting S exsolution during magma ascent, which further enhances the reduction of fO2. For the evolved MIs of 2002–2013 eruptions, magma differentiation may therefore have played a crucial role in decreasing redox conditions and favouring efficient S degassing. Differently, during the unusual FS eruption, only limited melt evolution is observed and S exsolution seems to have been triggered by a major pressure decrease accompanied by H2O and CO2 exsolution during fast magmatic ascent.
    Description: Published
    Description: egaa095
    Description: 4V. Processi pre-eruttivi
    Description: JCR Journal
    Keywords: melt inclusions ; sulphur solubility experiments ; XANES ; Mt. Etna ; 04.08. Volcanology
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  • 21
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    Importance of earthquake rupture geometry on tsunami modelling: the Calabrian Arc subduction interface (Italy) case study (2020)
    Oxford University Press
    Details
    Publication Date: 2020-10-16
    Description: The behaviour of tsunami waves at any location depends on the local morphology of the coasts, the encountered bathymetric features, and the characteristics of the source. However, the importance of accurately modelling the geometric properties of the causative fault for simulations of seismically induced tsunamis is rarely addressed. In this work, we analyse the effects of using two different geometric models of the subduction interface of the Calabrian Arc (southern Italy, Ionian Sea) onto the simulated tsunamis: a detailed 3-D subduction interface obtained from the interpretation of a dense network of seismic reflection profiles, and a planar interface that roughly approximates the 3-D one. These models can be thought of as representing two end-members of the level of knowledge of fault geometry. We define three hypothetical earthquake ruptures of different magnitudes (Mw 7.5, 8.0, 8.5) on each geometry. The resulting tsunami impact is evaluated at the 50-m isobath in front of coastlines of the central and eastern Mediterranean. Our results show that the source geometry imprint is evident on the tsunami waveforms, as recorded at various distances and positions relative to the source. The absolute differences in maximum and minimum wave amplitudes locally exceed one metre, and the relative differences remain systematically above 20 per cent with peaks over 40 per cent. We also observe that tsunami energy directivity and focusing due to bathymetric waveguides take different paths depending on which fault is used. Although the differences increase with increasing earthquake magnitude, there is no simple rule to anticipate the different effects produced by these end-member models of the earthquake source. Our findings suggest that oversimplified source models may hinder our fundamental understanding of the tsunami impact and great care should be adopted when making simplistic assumptions regarding the appropriateness of the planar fault approximation in tsunami studies. We also remark that the geological and geophysical 3-D fault characterization remains a crucial and unavoidable step in tsunami hazard analyses.
    Description: Published
    Description: 1805–1819
    Description: 3T. Sorgente sismica
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 22
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    Greenland uplift and regional sea–level changes from ICESat observations and GIA modeling (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2020-12-14
    Description: We study the implications of a recently published mass balance of the Greenland ice sheet (GrIS), derived from repeated surface elevation measurements from NASA’s ice cloud and land elevation satellite (ICESat) for the time period between 2003 and 2008. To characterize the effects of this new, high-resolution GrIS mass balance, we study the time-variations of various geophysical quantities in response to the current mass loss. They include vertical uplift and subsidence, geoid height variations, global patterns of sea level change (or fingerprints), and regional sea level variations along the coasts of Greenland. Long-wavelength uplifts and gravity variations in response to current or past ice thickness variations are obtained solving the sea level equation, which accounts for both the elastic and the viscoelastic components of deformation. To capture the short-wavelength components of vertical uplift in response to current ice mass loss, which is not resolved by satellite gravity observations, we have specifically developed a high-resolution regional elastic rebound (ER) model. The elastic component of vertical uplift is combined with estimates of the viscoelastic displacement fields associated with the process of glacial-isostatic adjustment (GIA), according to a set of published ice chronologies and associated mantle rheological profiles. We compare the sensitivity of global positioning system (GPS) observations along the coasts of Greenland to the ongoing ER and GIA. In notable contrast with past reports, we show that vertical velocities obtained by GPS data from five stations with sufficiently long records and from one tide gauge at the GrIS margins can be reconciled with model predictions based on the ICE-5G deglaciation model and the ER associated with the new ICESat-derived mass balance.
    Description: Published
    Description: 1457-1474
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Sea level change ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
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  • 23
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    A smoothed stochastic earthquake rate model considering seismicity and fault moment release for Europe (2014)
    Wiley-Blackwell
    Details
    Publication Date: 2020-12-15
    Description: We present a time-independent gridded earthquake rate forecast for the European region including Turkey. The spatial component of our model is based on kernel density estimation techniques, which we applied to both past earthquake locations and fault moment release on mapped crustal faults and subduction zone interfaces with assigned slip rates. Our forecast relies on the assumption that the locations of past seismicity is a good guide to future seismicity, and that future large-magnitude events occur more likely in the vicinity of known faults. We show that the optimal weighted sum of the corresponding two spatial densities depends on the magnitude range considered. The kernel bandwidths and density weighting function are optimized using retrospective likelihood-based forecast experiments. We computed earthquake activity rates (a- and b-value) of the truncated Gutenberg–Richter distribution separately for crustal and subduction seismicity based on a maximum likelihood approach that considers the spatial and temporal completeness history of the catalogue. The final annual rate of our forecast is purely driven by the maximum likelihood fit of activity rates to the catalogue data, whereas its spatial component incorporates contributions from both earthquake and fault moment-rate densities. Our model constitutes one branch of the earthquake source model logic tree of the 2013 European seismic hazard model released by the EU-FP7 project ‘Seismic HAzard haRmonization in Europe’ (SHARE) and contributes to the assessment of epistemic uncertainties in earthquake activity rates. We performed retrospective and pseudo-prospective likelihood consistency tests to underline the reliability of our model and SHARE’s area source model (ASM) using the testing algorithms applied in the collaboratory for the study of earthquake predictability (CSEP). We comparatively tested our model’s forecasting skill against the ASM and find a statistically significant better performance for testing periods of 10–20 yr. The testing results suggest that our model is a viable candidate model to serve for long-term forecasting on timescales of years to decades for the European region.
    Description: EC-Research FP7-projects, SHARE, under grant agreement No. 226967 and NERA, under grant agreement No. 262330
    Description: Published
    Description: 1159-1172
    Description: 2T. Tettonica attiva
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: Probabilistic forecasting ; Statistical seismology ; Europe ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
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  • 24
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    Systemic seismic risk assessment of road networks in urban areas (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2021-03-18
    Description: This article presents an integrated approach for the probabilistic systemic risk analysis of a road network considering spatial seismic hazard with correlation of ground motion intensities, vulnerability of the network components, and the effect of interactions within the network, as well as, between roadway components and built environment to the network functionality. The system performance is evaluated at the system level through a global connectivity performance indicator, which depends on both physical damages to its components and induced functionality losses due to interactions with other systems. An object-oriented modeling paradigm is used, where the complex problem of several interacting systems is decomposed in a number of interacting objects, accounting for intra- and interdependencies between and within systems. Each system is specified with its components, solving algorithms, performance indicators and interactions with other systems. The proposed approach is implemented for the analysis of the road network in the city of Thessaloniki (Greece) to demonstrate its applicability. In particular, the risk for the road network in the area is calculated, specifically focusing on the short-term impact of seismic events (just after the earthquake). The potential of road blockages due to collapses of adjacent buildings and overpass bridges is analyzed, trying to individuate possible criticalities related to specific components/subsystems. The application can be extended based on the proposed approach, to account for other interactions such as failure of pipelines beneath the road segments, collapse of adjacent electric poles, or malfunction of lighting and signaling systems due to damage in the electric power network.
    Description: Published
    Description: 524–540
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: Systemic vulnerability ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
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    On the Heterogeneity of the Earthquake rupture (2021)
    Oxford University Press
    Details
    Publication Date: 2021-04-14
    Description: The scaling of earthquake parameters with seismic moment and its interpretation in terms of self- similarity is still debated in the literature. We address this question by examining a worldwide compilation of corner frequency-based and elastic rebound theory (ERT)-based fault slip, area and stress drop values for earthquakes ranging in magnitude from -0.7 to 7.8. We find that corner frequency estimates of slip (and stress drop) scale differently than those inferred from the ERT approach, where the latter deviates from the generally accepted constant stress drop behavior of so- called self-similar scaling models. We also find that average slips from finite-source models are consistent with corner frequency scaling, whereas peak slip values are more consistent with the ERT scaling. The different scaling of corner frequency- and ERT-based estimates of slip and stress drop with earthquake size is interpreted in terms of heterogeneity of the rupture process. ERT-based estimates of stress drop decrease with seismic moment suggesting a self-affine behavior. Despite the inferred heterogeneity at all scales, we do not observe a clear effect on the Brune stress drop scaling with earthquake size.
    Description: Published
    Description: 1771–1781
    Description: 2T. Deformazione crostale attiva
    Description: JCR Journal
    Keywords: Earthquake dynamics ; Earthquake source observations ; Dynamics and mechanics of faulting ; 04.06. Seismology
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  • 26
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    High frequency attenuation of shear waves in Southeastern Alps and Northern Dinarides (2011)
    Wiley-Blackwell
    Details
    Publication Date: 2021-06-08
    Description: We investigated the high frequency attenuation of S-waves in Southeastern Alps and Northern External Dinarides using waveforms from 331 earthquakes (3.0〈 Mw〈 6.5). The spectral decay parameter, k, was computed using 1345 three component high quality records, collected by the Italian Strong Motion Network (RAN) and by the Short-Period Seismometric Network of North-Eastern Italy (NEI) in the period 1976-2007. Weak motion data from 11 stations of the NEI network and strong motion data collected by 5 accelerometers of the RAN were analyzed. The k parameter was estimated in the 0-250 Km distance range, in a frequency band extending from the corner frequency of the event up to 25 or 45 Hz, using the amplitude acceleration Fourier spectra of S-waves. The observed record-to-record variability of k was modeled by applying a generalized inversion procedure, using both parametric and non-parametric approaches. Our results evidence that k is independent on earthquake size, while it shows both site and distance dependence. Stations of the NEI network present the same increase of k with epicentral distance, Re, and show values of the zero-distance k parameter, k0(S), between 0.017 and 0.053 s. For the whole region, the k increase with distance can be described through a linear model with slope dk/dRe = (1.4±0.1)x10^(-4) s/Km. Assuming an average S-wave velocity, 〈Vs〉=3.34 Km/s between 5 and 15 Km depth, we estimate an average frequency independent quality factor, 〈Qi〉=2140, for the corresponding crustal layer. The non-parametric approach evidences a weak positive concavity of the curve that describes the k increase with Re at about 90 Km distance. This result can be approximated through a piecewise linear function with slopes of 1.0x10^(-4) s/Km and 1.7x10^(-4) s/Km, in accordance with a three layers model where moving from the intermediate to the bottom layer both 〈Qi〉 and 〈Vs〉 decrease. Two regional dependences were found: data from earthquakes located westward to the NEI network evidence weaker attenuation properties, probably because of S-wave reflections from different part of the Moho discontinuity under the eastern Po Plain, at about 25-30 Km depth, while earthquakes located eastward (in western Slovenia), where the Moho deepens up to 45-50 Km, evidence a higher attenuation. Moreover, the k estimates obtained with data from earthquakes located in the area of the 1998 (Mw=5.7) and 2004 (Mw=5.2) Kobarid events are 0.017 s higher than the values predicted for the whole region, probably because of the high level of fracturing that characterizes fault zones. The comparison between measured and theoretical values of k, computed at a few stations with available S-wave velocity profiles, reveals that the major contribution to the total k0(S) is due to the sedimentary column (from surface to 800 m depth). The hard rock section contribution is limited to 0.005 s, in accordance with a maximum contribution of 0.010 s predicted by the non-parametric inversion.
    Description: Published
    Description: 1393-1416
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: open
    Keywords: Earthquake source observations ; Body waves ; Seismic attenuation ; Site effects ; Wave propagation ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 27
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    BUILDING MATERIALS OF THE THEATRE OF MARCELLUS, ROME* (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2021-06-22
    Description: The building materials of the Theatre of Marcellus, 44–11 BCE, reflect Roman builders’ careful selections of tuff and travertine for dimension stone and volcanic aggregates for pozzolanic concretes. The vitric–lithic–crystal Tufo Lionato tuff dimension stone contains a high proportion of lava lithic fragments, which increase its compressive strength and decrease water sorption, enhancing durability. Sophisticated installations of travertine dimension stone reinforce the tuff masonry, which is integrated with durable concrete walls and barrel vaults. The pozzolanic mortars of the concretes contain harenae fossiciae mainly from the intermediate alteration facies of the mid-Pleistocene, scoriaceous Pozzolane Rosse pyroclastic flow. They have pervasive interpenetrating pozzolanic cements, including strätlingite, similar to highquality, imperial era mortars. Concrete walls are faced with refined Tufo Lionato opus reticulatum and tufelli, and opus testaceum of fired, greyish-yellow brick. The exploratory concrete masonry, which includes some of the earliest examples of brick facings and strätlingite cements in Rome, and the integration of these materials in complex architectural elements and internal spaces, reflect the highly skilled workmanship, rigorous work-site management and technical supervision of Roman builders trained in republican era methods and materials.
    Description: Published
    Description: 728–742
    Description: JCR Journal
    Description: restricted
    Keywords: VOLCANIC TUFF MASONRY ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous
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  • 28
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    A continuous palaeosecular variation record of the last four millennia from the Augusta Bay (Sicily, Italy) (2011)
    Wiley-Blackwell
    Details
    Publication Date: 2021-06-07
    Description: We present a high-resolution palaeomagnetic and rock magnetic study of two cores, MS06 and MS06-SW (6.7 and 1.1 m long, respectively), collected at 72 m below sea level in the Augusta Bay shelf (Eastern Sicily, Ionian Sea, Italy) about 2.3 kmfrom the coastline. Geophysical surveying carried out in the sampling area highlighted the presence of a homogeneous sedimentary sequence that most likely was deposited after the Last Glacial Maximum and was not affected by anthropogenic disturbances. The two cores penetrated a monotonous mud sedimentary sequence, interrupted at ∼3 m depth by a 3–4-cm-thick volcanic sandy layer that is correlated with the tephra fallout deposit produced by the 122 BC plinian eruption of Mt Etna. This tephra, along with radiocarbon dating of nine marine shells and with radioactive tracers for the uppermost 0.3 m (210Pb and 137Cs), provide the chronological constraints for the stratigraphic sequence that resulted younger than 4500 yr BP. Palaeomagnetic and rock magnetic data show that the sample sequence is magnetically homogeneous. A single peak of high magnetic mineral concentration is present and corresponds to the volcanic sandy layer. Palaeomagnetic data allowed the identification of a well-defined characteristic remanent magnetization that provides a high-resolution record of palaeosecular variation (PSV) at the sampling site. The reconstructed PSV curve is in good agreement with the available regional reference PSV curves and with the prediction from recent PSV modelling for Europe. The palaeomagnetic data obtained in this study on the one hand support and refine the age model for the cores, derived from other independent constraints, and on the other hand provide an original high-resolution PSV curve that can serve as a reference for the central Mediterranean over the last 4 ka.
    Description: Published
    Description: 191 - 202
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: Palaeointensity ; Palaeomagnetic secular variation ; Marine magnetics and palaeomagnetics ; Europe ; 04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism
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  • 29
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    Rotational motions from the 2016, Central Italy seismic sequence, as observed by an underground ring laser gyroscope (2019)
    Oxford University Press
    Details
    Publication Date: 2021-06-21
    Description: We present the analysis of rotational and translational ground motions from earthquakes recorded during October–November 2016, in association with the Central Italy seismic sequence. We use co-located measurements of the vertical ground rotation rate from a large ring laser gyroscope and the three components of ground velocity from a broad-band seismometer. Both instruments are positioned in a deep underground environment, within the Gran Sasso National Laboratories of the Istituto Nazionale di Fisica Nucleare. We collected dozens of events spanning the 3.5–5.9 magnitude range and epicentral distances between 30 and 70 km. This data set constitutes an unprecedented observation of the vertical rotational motions associated with an intense seismic sequence at local distance. Under the plane-wave approximation we process the data set in order to get an experimental estimation of the events backazimuth. Peak values of rotation rate (PRR) and horizontal acceleration (PGA) are markedly correlated, according to a scaling constant which is consistent with previous measurements from different earthquake sequences. We used a prediction model in use for Italy to calculate the expected PGA at the recording site, obtaining consequently predictions for PRR. Within the modelling uncertainties, predicted rotations are consistent with the observed ones, suggesting the possibility of establishing specific attenuation models for ground rotations, like the scaling of peak velocity and peak acceleration in empirical ground-motion prediction relationships. In a second step, after identifying the direction of the incoming wavefield, we extract phase-velocity data using the spectral ratio of the translational and rotational components. This analysis is performed over time windows associated with the P-coda, S-coda and Lg phase. Results are consistent with independent estimates of shear wave velocities in the shallow crust of the Central Apennines
    Description: Published
    Description: 705-715
    Description: 4T. Sismicità dell'Italia
    Description: JCR Journal
    Keywords: Rotational seismology ; Surface waves and free oscillations ; Wave propagation
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  • 30
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    Impact of appendicularians on detritus and export fluxes: a model approach at Dyfamed site (2012)
    Oxford University Press
    Details
    Publication Date: 2020-11-26
    Description: So far, the role of appendicularians in the biogeochemical cycling of organic matter has been largely overlooked. Appendicularians represent only a fraction of total mesozooplankton biomass, however these ubiquitous zooplankters have very high filtration and growth rates compared to copepods, and produce numerous fecal pellets and filtering houses contributing to export production by aggregating small marine particles. To study their quantitative impact on biogeochemical flux, we have included this group in the biogeochemical flux model, using a recently developed ecophysiological model. One-dimensional annual simulations of the pelagic ecosystem including appendicularians were conducted with realistic surface forcing for the year 2000, using data from the DyFAMed open ocean station. The appendicularian grazing impact was generally low, but appendicularians increased detritus production by 8% and export production by 55% compared to a simulation without appendicularians. Therefore, current biogeochemical models lacking appendicularians probably under, or misestimate the detritus and export production by omitting the pathway from small-sized plankton to fast sinking detritus. Detritus production and export rates are 60% lower than the estimates from mesotrophic sites, showing that appendicularians’ role is lower but still significant in oligotrophic environments. The simulated annual export at 200 m exceeds sediment trap values by 44%, suggesting an intense degradation during the sinking of appendicularian detritus, supported by observations made at other sites. Thus, degradation and grazing of appendicularian detritus need better quantification if we are to accurately assess the role of appendicularia in export flux.
    Description: EU-FP6 project SESAME GOCE-036949
    Description: Published
    Description: 855-872
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: reserved
    Keywords: BFM ; zooplankton ; 03. Hydrosphere::03.01. General::03.01.01. Analytical and numerical modeling ; 03. Hydrosphere::03.01. General::03.01.07. Physical and biogeochemical interactions ; 03. Hydrosphere::03.04. Chemical and biological::03.04.01. Biogeochemical cycles ; 03. Hydrosphere::03.04. Chemical and biological::03.04.04. Ecosystems
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  • 31
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    Back to the future: old methods for new estimation and test of the Gutenberg–Richter b-value for catalogues with variable completeness (2020)
    Oxford University Press
    Details
    Publication Date: 2020-11-11
    Description: This article has been accepted for publication in Geophysical Journal International ©: 2021 The Author(s) 2020. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
    Description: In this short paper we show how to use the classical maximum likelihood estimation procedure for the b-value of the Gutenberg–Richter law for catalogues with different levels of completeness. With a simple correction, that is subtracting the relative completeness level to each magnitude, it becomes possible to use the classical approach. Moreover, this correction allows to adopt the testing procedures, initially made for catalogues with a single level of completeness, for catalogues with different levels of completeness too.
    Description: Published
    Description: 337–339
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: JCR Journal
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  • 32
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    Ground structure imaging by inversions of Rayleigh wave ellipticity: sensitivity analysis and application to European strong-motion sites (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2020-12-14
    Description: The knowledge of the local soil structure is important for the assessment of seismic hazards. A widespread, but time-consuming technique to retrieve the parameters of the local underground is the drilling of boreholes. Another way to obtain the shear wave velocity profile at a given location is the inversion of surface wave dispersion curves. To ensure a good resolution for both superficial and deeper layers, the used dispersion curves need to cover a wide frequency range. This wide frequency range can be obtained using several arrays of seismic sensors or a single array comprising a large number of sensors. Consequently, these measurements are time-consuming. A simpler alternative is provided by the use of the ellipticity of Rayleigh waves. The frequency dependence of the ellipticity is tightly linked to the shear wave velocity profile. Furthermore, it can be measured using a single seismic sensor. As soil structures obtained by scaling of a given model exhibit the same ellipticity curve, any inversion of the ellipticity curve alone will be ambiguous. Therefore, additional measurements which fix the absolute value of the shear wave velocity profile at some points have to be included in the inversion process. Small-scale spatial autocorrelation measurements or MASW measurements can provide the needed data. Using a theoretical soil structure, we show which parts of the ellipticity curve have to be included in the inversion process to get a reliable result and which parts can be omitted. Furthermore, the use of autocorrelation or high-frequency dispersion curves will be highlighted. The resulting guidelines for inversions including ellipticity data are then applied to real data measurements collected at 14 different sites during the European NERIES project. It is found that the results are in good agreement with dispersion curve measurements. Furthermore, the method can help in identifying the mode of Rayleigh waves in dispersion curve measurements.
    Description: Published
    Description: 207-229
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: Inverse theory Surface waves and free oscillations Site effects Computational seismology Wave propagation ; 04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods
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  • 33
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    Seismic energy envelopes in volcanic media: in need of boundary conditions (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2020-12-15
    Description: Seismogram envelopes recorded at Campi Flegrei caldera show diffusive characteristics as well as steep amplitude increases in the intermediate and late coda, which can be related to the presence of a non-uniformly scattering medium. In this paper, we first show the results of a simulation with a statistical model considering anisotropic scattering interactions, in order to match coda-envelope duration and shape.We consider as realistic parameters for a volcanic caldera the presence of large square root velocity fluctuations (10 per cent) and two typical correlation lengths for such an heterogeneous crust, a = 0.1 and 1 km. Then, we propose the inclusion of a diffusive boundary condition in the stochastic description of multiple scattering, in order to model intermediate and late coda intensities, and particularly the sharp intensity peaks at some stations in the caldera. Finally, we show that a reliable 2-D synthetic model of the envelopes produced by earthquakes vertically sampling a small region can be obtained including a single drastic change of the scattering properties of the volcano, that is, a caldera rim of radius 3 km, and sections varying between 2 and 3 km. These boundary conditions are diffusive, which signifies that the rim must have more scattering potential than the rest of the medium, with its diffusivity 2–3 orders of magnitude lower than the one of the background medium, so that the secondary sources on its interface(s) could enhance coda intensities. We achieve a good first-order model of high-frequency (18 Hz) envelope broadening adding to the Monte Carlo solution for the incident flux the secondary source effects produced by a closed annular boundary, designed on the caldera rim signature at 1.5 km depth. At lower frequencies (3 Hz) the annular boundary controls the intermediate and late coda envelope behaviour, in a way similar to an extended diffusive source. In our interpretation, the anomalous intensities observed at several stations and predicted by the final Monte Carlo solutions are mainly due to the diffusive transmission reflection from a scattering object of increased scattering power, and are controlled by its varying thickness.
    Description: This work was carried out under the HPC-Europa2 project (project number: 228398) with the support of the European Commission Capacities Area-Research Infrastructures Initiative. We thank the whole staff at EPCC (Edinburgh Parallel Computing Centre) in Edinburgh and particularly Dr. Adam Carter for their help in both developing and parallelizing the code. The challenging comments and suggestions of the editor and two anonymous reviewers helped both in focusing the aim and in overcoming the strong limits of a previous version of the paper.
    Description: Published
    Description: 1102–1119
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: restricted
    Keywords: Numerical solutions; ; Seismic anisotropy; ; Seismic attenuation ; Seismic tomography ; Wave scattering and diffraction ; Calderas ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 34
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    Good practices in PSHA: declustering, b-value estimation, foreshocks and aftershocks inclusion; a case study in Italy (2020)
    Oxford University Press
    Details
    Publication Date: 2020-12-21
    Description: This article has been accepted for publication in Geophysical Journal International. Published by Oxford University Press on behalf of the Royal Astronomical Society.
    Description: The classical procedure of the Probabilistic Seismic Hazard Analysis (PSHA) requires a Poissonian distribution of earthquakes. Seismic catalogs follow a Poisson distribution just after the application of a declustering algorithm that leaves only one earthquake for each seismic sequence (usually the stronger, i.e. the main shock). Removing earthquakes from the seismic catalogs leads to underestimation of the annual rates of the events and consequently associate with low seismic hazard as indicated by several studies. In this study, we aim investigating the performance of two declustering methods on the Italian instrumental catalog and the impact of declustering on estimation of the b-value and on the seismic hazard analysis. To this end, first the spatial variation in the seismicity rate was estimated from the declustered catalogs using the adaptive smoothed seismicity approach, considering small earthquakes (Mw≥3.0). We then corrected the seismicity rates using new approach that allows for counting all events in the complete seismic catalog by simply changing the magnitude frequency distribution. The impact of declustering on seismic hazard analysis is illustrated using PSHA maps in terms of peak ground acceleration (PGA) and spectral acceleration (SA) in 2 s, with 10% and 2% probability of exceedance in 50 years, for Italy. We observed that the hazard calculated from the declustered catalogs was always lower than the hazard computed using the complete catalog. These results are in agreement with previous results obtained in different parts of the world.
    Description: Published
    Description: 1174–1187
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: JCR Journal
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  • 35
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    Stable isotopes of pedogenic carbonates from the Somma–Vesuvius area, southern Italy, over the past 18 kyr: palaeoclimatic implications (2016)
    Wiley-Blackwell
    Details
    Publication Date: 2021-04-07
    Description: Stable isotopes were measured in the carbonate and organic matter of palaeosols in the Somma–Vesuvius area, southern Italy in order to test whether they are suitable proxy records for climatic and ecological changes in this area during the past 18000 yr. The ages of the soils span from ca. 18 to ca. 3 kyr BP. Surprisingly, the Last Glacial to Holocene climate transition was not accompanied by significant change in d18O of pedogenic carbonate. This could be explained by changes in evaporation rate and in isotope fractionation between water and precipitated carbonate with temperature, which counterbalanced the expected change in isotope composition of meteoric water. Because of the rise in temperature and humidity and the progressive increase in tree cover during the Holocene, the Holocene soil carbonates closely reflect the isotopic composition of meteoric water. A cooling of about 2°C after the Avellino eruption (3.8 ka) accounts for a sudden decrease of about 1‰ in d18O of pedogenic carbonate recorded after this eruption. The d13C values of organic matter and pedogenic carbonate covary, indicating an effective isotope equilibrium between the organic matter, as the source of CO2, and the pedogenic carbonate. Carbon isotopes suggest prevailing C3 vegetation and negligible mixing with volcanogenic or atmospheric CO2.
    Description: Published
    Description: 813-824
    Description: 1V. Storia e struttura dei sistemi vulcanici
    Description: JCR Journal
    Description: restricted
    Keywords: stable isotope ; palaeosols ; Somma–Vesuvius ; palaeoclimate ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous
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  • 36
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    Crustal and uppermost mantle shear wave velocity structure beneath the Middle East from surface wave tomography (2021)
    Oxford University Press
    Details
    Publication Date: 2021-05-12
    Description: We have constructed a 3-D shear wave velocity (Vs) model for the crust and uppermost mantle beneath the Middle East using Rayleigh wave records obtained from ambient-noise cross-correlations and regional earthquakes. We combined one decade of data collected from 852 permanent and temporary broad-band stations in the region to calculate group-velocity dispersion curves. A compilation of 〉54 000 ray paths provides reliable group-velocity measurements for periods between 2 and 150 s. Path-averaged group velocities calculated at different periods were inverted for 2-D group-velocity maps. To overcome the problem of heterogeneous ray coverage, we used an adaptive grid parametrization for the group-velocity tomographic inversion. We then sample the period-dependent group-velocity field at each cell of a predefined grid to generate 1-D group-velocity dispersion curves, which are subsequently inverted for 1-D Vs models beneath each cell and combined to approximate the 3-D Vs structure of the area. The Vs model shows low velocities at shallow depths (5–10 km) beneath the Mesopotamian foredeep, South Caspian Basin, eastern Mediterranean and the Black Sea, in coincidence with deep sedimentary basins. Shallow high-velocity anomalies are observed in regions such as the Arabian Shield, Anatolian Plateau and Central Iran, which are dominated by widespread magmatic exposures. In the 10–20 km depth range, we find evidence for a band of high velocities (〉4.0 km s–1) along the southern Red Sea and Arabian Shield, indicating the presence of upper mantle rocks. Our 3-D velocity model exhibits high velocities in the depth range of 30–50 km beneath western Arabia, eastern Mediterranean, Central Iranian Block, South Caspian Basin and the Black Sea, possibly indicating a relatively thin crust. In contrast, the Zagros mountain range, the Sanandaj-Sirjan metamorphic zone in western central Iran, the easternmost Anatolian plateau and Lesser Caucasus are characterized by low velocities at these depths. Some of these anomalies may be related to thick crustal roots that support the high topography of these regions. In the upper mantle depth range, high-velocity anomalies are obtained beneath the Arabian Platform, southern Zagros, Persian Gulf and the eastern Mediterranean, in contrast to low velocities beneath the Red Sea, Arabian Shield, Afar depression, eastern Turkey and Lut Block in eastern Iran. Our Vs model may be used as a new reference crustal model for the Middle East in a broad range of future studies.
    Description: Published
    Description: 1349-1365
    Description: 1T. Struttura della Terra
    Description: JCR Journal
    Keywords: 04.01. Earth Interior ; 04.06. Seismology
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    A performance-based framework for adaptive seismic aftershock risk assessment (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2021-06-22
    Description: Operative seismic aftershock risk forecasting can be particularly useful for rapid decision-making in the presence of an ongoing sequence. In such a context, limit state first-excursion probabilities (risk) for the forecasting interval (a day) can represent the potential for progressive state of damage in a structure. This work lays out a performance-based framework for adaptive aftershock risk assessment in the immediate post-mainshock environment. A time-dependent structural performance variable is adopted in order to measure the cumulative damage in a structure. A set of event-dependent fragility curves as a function of the first-mode spectral acceleration for a prescribed limit state is calculated by employing back-to-back non- linear dynamic analyses. An epidemic-type aftershock sequence model is employed for estimating the spatio-temporal evolution of aftershocks. The event-dependent fragility curves for a given limit state are then integrated together with the probability distribution of aftershock spectral acceleration based on the epidemic-type aftershock sequence aftershock hazard. The daily probability of limit state first-excursion is finally calculated as a weighted combination of the sequence of limit state probabilities conditioned on the num- ber of aftershocks. As a numerical example, daily aftershock risk is calculated for the L’Aquila 2009 aftershock sequence (central Italy). A representative three-story reinforced concrete frame with infill panels, which has cyclic strength and stiffness degradation, is used in order to evaluate the progressive damage. It is observed that the proposed framework leads to a sound forecasting of limit state first-excursion in the structure for two limit states of significant damage and near collapse. Copyright © 2014 John Wiley & Sons, Ltd.
    Description: Published
    Description: 2179–2197
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: reserved
    Keywords: aftershock ; time-dependent reliability ; seismic risk ; etas modeling ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
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  • 38
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    The Holocene temperature conundrum (2014)
    National Academy of Sciences
    In:  EPIC3PNAS, National Academy of Sciences, 111(34), pp. E3501-E3505, ISSN: 0027-8424
    Details
    Publication Date: 2016-12-09
    Description: A recent temperature reconstruction of global annual temperature shows Early Holocene warmth followed by a cooling trend through the Middle to Late Holocene [Marcott SA, et al., 2013, Science 339(6124):1198–1201]. This global cooling is puzzling because it is opposite from the expected and simulated global warming trend due to the retreating ice sheets and rising atmospheric greenhouse gases. Our critical reexamination of this contradiction between the reconstructed cooling and the simulated warming points to potentially significant biases in both the seasonality of the proxy reconstruction and the climate sensitivity of current climate models.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 39
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    Chapter 16 Harmful Algal Species Fact Sheets: Alexandrium (2018)
    Wiley-Blackwell
    In:  EPIC3Harmful Algal Blooms: A Compendium Desk Reference, Wiley-Blackwell, 12 p., pp. 563-574, ISBN: 978-1-118-99465-8
    Details
    Publication Date: 2018-06-28
    Description: The genus Alexandrium (Halim) is perhaps the most intensively studied among toxic marine dinoflagellates. This is largely attributable to the devastating consequences of toxigenic blooms of this genus, with human poisonings from contaminated seafood, primarily from shellfish and more rarely from finfish; socio–economic losses to the aquaculture and fisheries industries; marine faunal mortalities; and food web disruptions common in coastal waters throughout the world. Members of this genus are globally distributed from the Arctic to the tropics, and in both hemispheres from sub–polar through temperate to sub–tropical to tropicalwaters. At least four distinct groups of marine phycotoxins are associated with various Alexandrium species, along with poorly characterized bioactive compounds (allelochemicals) that may affect species interactions among the plankton. According to the most recent iteration of the IOC–UNESCO reference list of toxic microalgae, there are now more than 30 recognized morphological species of Alexandrium, posing a daunting challenge for risk assessment and accurate identification in toxic phytoplankton monitoring programs.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , peerRev
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  • 40
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    Travel Time and Source Variation Explain the Molecular Transformation of Dissolved Organic Matter in an Alpine Stream Network (2020)
    Wiley-Blackwell
    In:  EPIC3JGR Biogeosciences, Wiley-Blackwell, ISSN: 2169-8961
    Details
    Publication Date: 2020-09-21
    Description: Streams and rivers are important components of the carbon cycle as they transport and transform dissolved organic matter (DOM). Using high‐resolution Fourier‐transform ion cyclotron resonance mass spectrometry, we studied the spatial distribution of DOM at the molecular level at more than 100 sites across a stream network during summer and winter baseflow. We developed a model approximating the time DOM spent in the fluvial network, a key constraint on the biogeochemical processing of DOM. Discharge‐weighted travel time explained the compositional changes of DOM, which differed markedly in summer and winter. We attribute these seasonal differences to variation in source material, putatively reflecting the dynamics of freshly produced DOM in summer and DOM with an imprint of leaf litter in winter. Hydrological mixing was an important driver of the spatial dynamics of DOM. From the convergence rate of DOM compound intensities to the network‐wide average, we inferred the spatial distribution of sources within the catchment. Finally, we estimated network‐wide apparent mass transfer coefficients (vf app) of individual DOM compounds, which describe the vertical velocity at which DOM compounds are removed by biotic and abiotic processes. We identified the oxidative state of carbon as an important factor explaining vf app, which we consequently attribute to biological uptake of thermodynamically favorable DOM compounds. This work contributes to our understanding of the spatial processes, temporal constraints, and chemical properties of DOM that regulate the transformation and diagenesis of DOM at the fluvial network scale.
    Repository Name: EPIC Alfred Wegener Institut
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    Scenario analysis can guide aquaculture planning to meet sustainable future production goals (2021)
    Oxford University Press
    In:  EPIC3ICES Journal of Marine Science, Oxford University Press, pp. 1-11, ISSN: 1054-3139
    Details
    Publication Date: 2021-07-23
    Description: Marine aquaculture holds great promise for meeting increasing demand for healthy protein that is sustainably produced, but reaching necessary production levels will be challenging. The ecosystem approach to aquaculture is a framework for sustainable aquaculture development that prioritizes multiple-stakeholder participation and spatial planning. These types of approaches have been increasingly used to help guide sustainable, persistent, and equitable aquaculture planning, but most countries have difficulties in setting or meeting longer-term development goals. Scenario analysis (SA) for future planning uses similar approaches and can complement holistic methods, such as the ecosystem approach to aquaculture framework, by providing a temporal analogue to the spatially robust design. Here we define the SA approach to planning in aquaculture, outline how SA can benefit aquaculture planning, and review how this tool is already being used. We track the use of planning tools in the 20 International Council for the Exploration of the Sea member nations, with particular attention given to Norway’s development goals to 2050. We conclude that employing a combination of an ecosystem framework with scenario analyses may help identify the scale of development aquaculture goals over time, aid in evaluating the feasibility of the desired outcomes, and highlight potential social-ecological conflicts and trade-offs that may otherwise be overlooked.
    Repository Name: EPIC Alfred Wegener Institut
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    The Mozambique Ridge: a document of massive multi-stage magmatism (2017)
    Oxford University Press
    In:  EPIC3Geophysical Journal International, Oxford University Press, 208(1), pp. 449-467, ISSN: 1365-246X
    Details
    Publication Date: 2016-12-03
    Description: The Mozambique Ridge, a prominent basement high in the southwestern Indian Ocean, consists of four major geomorphological segments associated with numerous phases of volcanic activity in the Lower Cretaceous. The nature and origin of the Mozambique Ridge have been intensely debated with one hypothesis suggesting a Large Igneous Province origin. High-resolution seismic reflection data reveal a large number of extrusion centres with a random distribution throughout the southern Mozambique Ridge and the nearby Transkei Rise. Intra-basement reflections emerge from the extrusion centres and are interpreted to represent massive lava flow sequences. Such lava flow sequences are characteristic of eruptions leading to the formation of continental and oceanic flood basalt provinces, hence supporting a Large Igneous Province origin of the Mozambique Ridge. We observe evidence for widespread post-sedimentary magmatic activity that we correlate with a southward propagation of the East African Rift System. Based on our volumetric analysis of the southern Mozambique Ridge we infer a rapid sequential emplacement between ~131 Ma and ~125 Ma, which is similar to the short formation periods of other Large Igneous Provinces like the Agulhas Plateau.
    Repository Name: EPIC Alfred Wegener Institut
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    Ocean surface temperature variability: Large model-data differences at decadal and longer periods (2014)
    National Academy of Sciences
    In:  EPIC3Proceedings of the National Academy of Sciences, National Academy of Sciences, ISSN: 0027-8424
    Details
    Publication Date: 2017-02-08
    Description: The variability of sea surface temperatures (SSTs) at multidecadal and longer timescales is poorly constrained, primarily because instrumental records are short and proxy records are noisy. Through applying a new noise filtering technique to a global network of late Holocene SST proxies, we estimate SST variability between annual and millennial timescales. Filtered estimates of SST variability obtained from coral, foraminifer, and alkenone records are shown to be consistent with one another and with instrumental records in the frequency bands at which they overlap. General circulation models, however, simulate SST variability that is systematically smaller than instrumental and proxy-based estimates. Discrepancies in variability are largest at low latitudes and increase with timescale, reaching two orders of magnitude for tropical variability at millennial timescales. This result implies major deficiencies in observational estimates or model simulations, or both, and has implications for the attribution of past variations and prediction of future change.
    Repository Name: EPIC Alfred Wegener Institut
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    Ocean acidification alleviates low-temperature effects on growth and photosynthesis of the red alga Neosiphonia harveyi (Rhodophyta) (2013)
    Oxford University Press
    In:  EPIC3Journal of Experimental Botany, Oxford University Press, ISSN: 0022-0957
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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  • 45
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    Impacts of Climate Change on the Southern Ocean (2017)
    Wiley-Blackwell
    In:  EPIC3Climate Change Impacts on Fisheries and Aquaculture: A Global Analysis, Climate Change Impacts on Fisheries and Aquaculture: A Global Analysis, Wiley-Blackwell, pp. 663-701, ISBN: 978-1-119-15404-4
    Details
    Publication Date: 2017-10-09
    Description: Exploitation of Southern Ocean marine resources began more than 200 years ago with the massive hunt for seals and whales. In the 1960s/70s, fisheries for finfish and krill entered Southern Ocean waters. Within a few years many fish populations were heavily overfished and dramatically depleted, and some of these stocks still did not recover. Today, fish stocks and fisheries activities are managed and monitored by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) which was established in 1982 to ensure sustainable exploitation and protection of the delicate marine ecosystem. Current target species include Mackerel icefish (Champsocephalus gunnari), Patagonian as well as Antarctic toothfish (Dissostichus eleginoides and D. mawsoni) and Antarctic krill (Euphausia superba). Most of these species are vulnerable to overfishing due to slow growth, late age at maturity, and rather low fecundity. This vulnerability might increase, as Southern Ocean living communities are currently also faced with alterations of their environment due to climate change, such as increasing water temperatures and decreasing sea ice. Species, including the ones targetted by fisheries, are well-adapted to their particular environmental conditions and are believed to be highly sensitive to changes because of their cold-adapted physiology, their life history traits, and their direct or indirect dependence on sea ice. The species will be exposed to several stressors at the same time, and fishing pressure, direct abiotic forcing and changes mediated via the food web might act synergistically and result in significant population declines. In particular the strongly sea ice-dependent Antarctic krill, a key species in the food web, might be adversely affected. Fish species seems to have low tolerance towards higher water temperatures and may thus, in the long run, be replaced by lower latitude species.
    Repository Name: EPIC Alfred Wegener Institut
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    The first known virus isolates from Antarctic sea ice have complex infection patterns (2018)
    Oxford University Press
    In:  EPIC3FEMS Microbiology Ecology, Oxford University Press, 94(4), pp. 1-15, ISSN: 1574-6941
    Details
    Publication Date: 2018-11-09
    Repository Name: EPIC Alfred Wegener Institut
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    Chapter 16: Harmful Algal Species Fact Sheets: Gymnodinium catenatum (2018)
    Wiley-Blackwell
    In:  EPIC3Harmful Algal Blooms: A Compendium Desk Reference, Wiley-Blackwell, 8 p., pp. 605-612, ISBN: 978-1-118-99465-8
    Details
    Publication Date: 2018-06-28
    Repository Name: EPIC Alfred Wegener Institut
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    Taxonomy of planktonic microbial eukaryotes (2017)
    Oxford University Press
    In:  EPIC3Marine Plankton, Marine Plankton, Oxford University Press, 704 p., ISBN: 9780199233267
    Details
    Publication Date: 2017-05-11
    Repository Name: EPIC Alfred Wegener Institut
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    Sampling, preservation, and counting of samples i) Phytoplankton (2017)
    Oxford University Press
    In:  EPIC3Marine Plankton, Marine Plankton, Oxford University Press, 704 p., ISBN: 9780199233267
    Details
    Publication Date: 2017-04-28
    Repository Name: EPIC Alfred Wegener Institut
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    Diatoms (2017)
    Oxford University Press
    In:  EPIC3Marine Plankton, Marine Plankton, Oxford University Press, 704 p., ISBN: 9780199233267
    Details
    Publication Date: 2017-05-11
    Repository Name: EPIC Alfred Wegener Institut
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    From COST 238 To COST 296: Four European COST Actions On Ionospheric Physics And Radio Propagation (2008)
    American Institute of Physics
    Details
    Publication Date: 2017-04-04
    Description: COST (Co-operation in the field of Scientific and Technical Research) is an important instrument supporting co-operation among scientists and researchers across Europe now joining 35 member countries. Scientific projects in the COST framework are called COST Actions and have the objectives embodied in their respective Memorandum of Understanding (MoU). The main objectives of the COST Actions within the European ionospheric and radio propagation community have been: to study the influence of upper atmospheric conditions on terrestrial and Earthspace communications, to develop methods and techniques to improve existing and generate new ionospheric and propagation models over Europe for telecommunication and navigation applications and to transfer the results to the appropriate national and international organizations, institutions and industry dealing with the modern communication systems. This paper summarises in brief the background and historical context of four ionospheric COST Actions and outlines their main objectives and results. In addition, the paper discusses the dissemination of the results and the collaboration among the participating institutions and researchers.
    Description: DRS Codem Systems Ball Aerospace Corporation University of Massachusetts Lowell
    Description: Published
    Description: Lowell, Massachusetts, U.S.A., April 29, 2007
    Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale
    Description: open
    Keywords: Physics of the Ionosphere ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous ; 05. General::05.07. Space and Planetary sciences::05.07.02. Space weather
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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    Imaging lateral heterogeneity in the northern Apennines from time reversal of reflected surface waves (2010)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Prominent arrivals in the coda of seismograms from the wider Alpine area can be associated with lateral reflections of Love waves at the northern Apennines mountain chain (Italy), where structural heterogeneity causes an abrupt contrast in phase velocity. We discuss an approach to image lateral heterogeneity from reflected surface waves using intermediate-period, three- component coda waveforms as sources for an adjoint wavefield that propagates the reflections backward in time. We numerically compute three-dimensional sensitivity kernels for the dependence of coda waveforms on P velocity, S velocity and density, based upon correlations between the adjoint and the regular forward wavefields. We consider synthetic coda waveforms for a simplified model of the northern Apennines, as well as real coda observations from five moderate magnitude earthquakes (M W 4.6–5.6) in the southern Alps. Wave propagation is simulated using the spectral-element method, for which a 3-D regional earth model is used in the case of real data. Single and combined event sensitivity kernels provide clear images of the reflectivity associated with the northern Apennines in kernels for density and S-wave speed. The kernels show that surface wave reflections occur near the axial zone of the mountain chain. Apart from the Apennines, the approach is able to image other smaller reflectivity patches from the coda waveforms, like the Ivrea zone in the southern Alps. Our coda misfit kernels can be integrated in a gradient-based waveform tomography, where they could enhance the shar pness of the model at lateral discontinuities.
    Description: Published
    Description: 543–554
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: Tomography; ; Computational seismology ; Wave scattering and diffraction ; Crustal structure ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
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    Gas hazard assessment at the Monticchio Mt. Vulture, a volcano in Southern Italy (2009)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Geochemical investigations have shown that there is a considerable inflow of gas into both crater lakes of Monticchio, Southern Italy. These lakes are located in two maars that formed 140 000 years ago during Mt. Vulture volcano s last eruptive activity. Isotopic analyses suggest that CO2 and helium are of magmatic origin; the latter displays 3He ⁄ 4He isotope ratios similar to those measured in olivines of the maar ejecta. In spite of the fact that the amount of dissolved gases in the water is less than that found in Lake Nyos (Cameroon), both the results obtained and the historical reports studied indicate that these crater lakes could be highly hazardous sites, even though they are located in a region currently considered inactive. This could be of special significance in very popular tourist areas such as the Monticchio lakes, which are visited by about 30 000 people throughout the summer, for the most part on Sundays.
    Description: Published
    Description: 83-87
    Description: 2.4. TTC - Laboratori di geochimica dei fluidi
    Description: JCR Journal
    Description: reserved
    Keywords: volcanic gases ; gas hazard ; crater lakes ; 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::04.08.08. Volcanic risk
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    Seismic moment tensors of the April 2009, L’Aquila (Central Italy), (2009)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: On 2009 April 6, the Central Apennines were hit by an Mw = 6.3 earthquake. The region had been shaken since 2008 October by seismic activity that culminated in two foreshocks with Mw 〉 4, 1 week and a few hours before the main shock. We computed seismic moment tensors for 26 events with Mw between 3.9 and 6.3, using the Regional Centroid Moment Tensor (RCMT) scheme. Most of these source parameters have been computed within 1 hr after the earthquake and rapidly revised successively. The focal mechanisms are all extensional, with a variable and sometimes significant strike-slip component. This geometry agrees with the NE–SW extensional deformation of the Apennines, known from previous seismic and geodetic observations. Events group into three clusters. Those located in the southern area have larger centroid depths and a wider distribution of T-axis directions. These differences suggest that towards south a different fault systemwas activated with respect to the SW-dipping normal faults beneath L’Aquila and more to the north.
    Description: In press
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: JCR Journal
    Description: open
    Keywords: moment tensor ; seismotectonics ; L'Aquila ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics
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    Experimental observation of stick-slip instability fronts (2010)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Stick-slip dynamic instability is a key mechanism governing frictional processes from microscale physics to earthquake faults and landslides; yet challenging questions are stil open about its nucleation and propagation dynamics. We present novel observations on laboratory experimental faults where spontaneously nucleating fractures are produced, describing (1) an initial quasistatic, stable rupture front accelerating to subshear and then intersonic velocity; 2) the arisal of a higher degree of complexity when the friction to prestress ratio is increased on the sliding surface. The complex behaviour includes stop and go sequences, irregular proportion and rerupturing episodes within short-time intervals, implying rapid restrengthening of the surface and the formation of self-healing pulses, reproducing experimentally for the first time a behaviour observed on seismic faults.
    Description: Published
    Description: 697-702
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Fractures and flow; friction; earthquake dynamics; Dynamics and mechanics of faulting ; 04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones
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    The Mw 6.3, 2009 L’Aquila earthquake: source, path and site effects from spectral analysis of strong motion data (2009)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: The strong motion data of 2009 April 6 L’Aquila (Central Italy) earthquake (Mw = 6.3) and of 12 aftershocks (4.1 ≤ Mw ≤ 5.6) recorded by 56 stations of the Italian strong motion network are spectrally analysed to estimate the source parameters, the seismic attenuation, and the site amplification effects. The obtained source spectra for S wave have stress drop values ranging from 2.4 to 16.8 MPa, being the stress drop of the main shock equal to 9.2 MPa. The spectral curves describing the attenuation with distance show the presence of shoulders and bumps, mainly around 50 and 150 km, as consequence of significant reflected and refracted arrivals from crustal interfaces. The attenuation in the first 50 km is well described by a quality factor equal to Q( f ) = 59 f 0.56 obtained by fixing the geometrical spreading exponent to 1. Finally, the horizontal-to-vertical spectral ratio provides unreliable estimates of local site effects for those stations showing large amplifications over the vertical component of motion.
    Description: Published
    Description: 1573–1579
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: open
    Keywords: Generalized inversion ; strong-motion ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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    Rock magnetism and palaeomagnetism of the Montalbano Jonico section (Italy): evidence for late diagenetic growth of greigite and implications for magnetostratigraphy (2010)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: The Montalbano Jonico (MJ) section, cropping out in Southern Italy, represents a potential candidate to define the Lower/Middle Pleistocene boundary and it has been proposed as a suitable Global Stratotype Section and Point (GSSP) of the Ionian Stage (Middle Pleistocene). The MJ section is the only continuous benthic and planktonic δ18O on-land reference in the Mediterranean area for the Mid-Pleistocene transition, spanning an interval between about 1240 and 645 ka. Combined biostratigraphy and sapropel chronology, tephra stratigraphy and complete high-resolution benthic and planktonic foraminiferal stable oxygen isotope records already provide a firm chronostratigraphic framework for the MJ section. However, magnetostratigraphy was still required to precisely locate the Brunhes-Matuyama transition and to mark the GSSP for the Ionian stage. We carried out a palaeomagnetic study of a subsection (Ideale section) of the MJ composite section, sampling 61 oriented cores from 56 stratigraphic levels spread over a ca. 80-m-thick stratigraphic interval that correlates to the oxygen isotopic stage 19 and should therefore include the Brunhes-Matuyama reversal. The palaeomagnetic data indicate a stable and almost single-component natural remanent magnetization (NRM). A characteristic remanent magnetization (ChRM) was clearly identified by stepwise demagnetization of the NRM. The ChRM declination values vary around 0◦ and the ChRM inclination around the expected value (59◦) for a geocentric axial dipole field at the sampling locality. This result indicates that the section has been remagnetized during the Brunhes Chron. A preliminary study of 27 additional not azimuthally oriented hand samples, collected at various levels from other parts of the MJ composite section, indicates that all the samples are of normal polarity and demonstrates that the remagnetization is widespread across the whole exposed stratigraphic sequence. A series of specific rock magnetic techniques were then applied to investigate the nature of the main magnetic carrier in the study sediments, and they suggest that the main magnetic mineral in the MJ section is the iron sulphide greigite (Fe3S4). Scanning electron microscope observations and elemental microanalysis reveal that greigite occurs both as individual euhedral crystals and in iron sulphides aggregates filling voids in the clay matrix. Therefore, we infer that the remagnetization of the section is due to the late-diagenetic growth of greigite under reducing conditions, most likely resulting in the almost complete dissolution of the original magnetic minerals. Iron sulphide formation in the MJ section can be linked to migration of mineralized fluids. Our inferred timing of the remagnetization associated with greigite growth represents the longest remanence acquisition delay documented in greigite-bearing clays of the Italian peninsula so far.
    Description: In press
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: open
    Keywords: Remagnetization ; 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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    A continuous palaeosecular variation record of the last four millennia from the Augusta Bay (Sicily, Italy) (2010)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We present a high-resolution palaeomagnetic and rock magnetic study of two cores, MS06 and MS06-SW (6.7 and 1.1 m long, respectively), collected at 72 m below sea level in the Augusta Bay shelf (Eastern Sicily, Ionian Sea, Italy) about 2.3 kmfrom the coastline. Geophysical surveying carried out in the sampling area highlighted the presence of a homogeneous sedimentary sequence that most likely was deposited after the Last Glacial Maximum and was not affected by anthropogenic disturbances. The two cores penetrated a monotonous mud sedimentary sequence, interrupted at ∼3 m depth by a 3–4-cm-thick volcanic sandy layer that is correlated with the tephra fallout deposit produced by the 122 BC plinian eruption of Mt Etna. This tephra, along with radiocarbon dating of nine marine shells and with radioactive tracers for the uppermost 0.3 m (210Pb and 137Cs), provide the chronological constraints for the stratigraphic sequence that resulted younger than 4500 yr BP. Palaeomagnetic and rock magnetic data show that the sample sequence is magnetically homogeneous. A single peak of high magnetic mineral concentration is present and corresponds to the volcanic sandy layer. Palaeomagnetic data allowed the identification of a well-defined characteristic remanent magnetization that provides a high-resolution record of palaeosecular variation (PSV) at the sampling site. The reconstructed PSV curve is in good agreement with the available regional reference PSV curves and with the prediction from recent PSV modelling for Europe. The palaeomagnetic data obtained in this study on the one hand support and refine the age model for the cores, derived from other independent constraints, and on the other hand provide an original high-resolution PSV curve that can serve as a reference for the central Mediterranean over the last 4 ka.
    Description: In press
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: Palaeomagnetic secular variation ; Palaeointensity ; Marine magnetics and palaeomagnetics ; Europe ; 04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism
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    Tropical Pacific-North Pacific teleconnection in a coupled GCM: Remote and local effects (2011)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: The connection between Tropical Pacific and North Pacific variability is investigated in a state-of-the art coupled ocean-atmosphere model, comparing two 20th century simulations at T30 and T106 atmospheric horizontal resolutions. Despite a better simulation of the frequency and the spatial distribution of the Tropical Pacific anomalies associated with the El Nino Southern Oscillation (ENSO) in the high-resolution experiment, the response in the North Pacific is scarcely different from the low-resolution experiment where the ENSO variability is weaker and at higher than observed frequency. In the North Pacific, the response of surface atmospheric fields to the variability in the Tropical Pacific appears to be affected by local coupling processes significantly different in the two experiments. The coupling between sea level pressure (SLP) and sea surface temperature (SST) in the North Pacific as well as the influence of the Tropical Pacific SST has been measured here by means of the ‘coupled manifold’ technique. In the low-resolution case the SLP variances linked to the fraction of North Pacific SST not influenced by the Tropical Pacific are weak suggesting that the remote influence is strong, consistently with the observations. On the contrary, in the high-resolution experiment the fractions and the patterns of the SLP variances due to the Tropical Pacific SST and those linked to the North Pacific SST are comparable. In the latter case, model systematic errors in the northwestern Pacific influences the local coupling processes thus triggering the remote response. We conclude that an increased atmospheric horizontal resolution does not reduce the coupled model systematic errors in the representation of the teleconnection between the North and the Tropical Pacific and that the validation of coupled models has to consider both remote and local processes.
    Description: Published
    Description: 1640-1653
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: open
    Keywords: Tropical Pacific-North Pacific teleconnection ; ENSO ; coupled GCMs ; 01. Atmosphere::01.01. Atmosphere::01.01.02. Climate ; 01. Atmosphere::01.01. Atmosphere::01.01.04. Processes and Dynamics ; 03. Hydrosphere::03.01. General::03.01.03. Global climate models
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    Volcanic edifice weakening via devolatilization reactions (2011)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Edifice instability, that can result in catastrophic flank collapse, is a fundamental volcanic hazard. The subvolcanic basement can encourage such instability, especially if it is susceptible to mechanical weakening by devolatilization reactions near magmatic temperatures. For this reason, understanding how the physical and chemical properties of representative lithologies deteriorate at high temperatures is potentially highly relevant for volcanic hazard mitigation. This is particularly true for sedimentary rock, commonly found underlying volcanic edifices worldwide, that undergo rapid deterioration even under modest temperatures. Therefore, here we present the first experimental study of devolatilization reactions, induced by magmatic temperatures, on sedimentary rock comprising a subvolcanic basement. Our results show that, for a marly limestone representative of the basement at Mt Etna, devolatilization reactions, namely the dehydroxylation of clay minerals and the decarbonation of calcium carbonate, result in a dramatic reduction of mechanical strength and seismic velocities. These temperature-driven reactions can promote volcanic instability at stresses much lower than previously estimated.
    Description: Published
    Description: 1073–1077
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: reserved
    Keywords: Phase transitions ; Experimental volcanism ; 04. Solid Earth::04.01. Earth Interior::04.01.04. Mineral physics and properties of rocks
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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    Optimal fault resolution in geodetic inversion of coseismic data (2011)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-03
    Description: With the continued growth in availability of DInSAR and GPS data, space based geodesy has been widely applied to image the coseismic displacement field and to retrieve the static dislocation over the fault plane for almost all the significant earthquakes of the past two decades. This is performed by linear data inversion over a set of subfaults, generally characterized by a constant and predefined or manually adjusted dimensions. In this paper we propose a new algorithm to automatically retrieve an optimized fault subdivision in the linear inversion of coseismic geodetic data. The code iteratively keeps the parameter resolution close to a predefined high value. We first discuss the rationale supporting our algorithm and, after a detailed description of its implementation, we analyze the advantages of its introduction in the data inversion. The algorithm was tested against an exhaustive range of synthetic and real datasets and fault mechanisms. Among them, we present the results for the Mw 6.2, 2009 L’Aquila (Central Italy) earthquake and compare the new and previously published slip distributions showing the disappearance of misleading slip pattern and the increased resolution for shallower zones.
    Description: Published
    Description: 529-538
    Description: 1.10. TTC - Telerilevamento
    Description: JCR Journal
    Description: open
    Keywords: fault modelling ; geodetic data inversion ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy
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  • 62
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    Fault geometry, coseismic-slip distribution and Coulomb stress change associated with the 2009 April 6, Mw 6.3, L’Aquila earthquake from inversion of GPS displacements (2011)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: The 2009 April 6, Mw= 6.3 L’Aquila earthquake occurred within a complex system of NW–SE trending normal faults in the Abruzzi Central Apennines (Italy). We analyse the coseismic deformation as measured by 〉70 global positioning system (GPS) stations, both from continuous and survey-mode networks, providing unprecedented details for a moderate normal faulting earthquake in Italy from GPS measurements. We use rectangular, uniform-slip, dislocations embedded in an elastic, homogeneous and isotropic half-space and a constrained, non-linear optimization algorithm, to solve for the best-fitting rectangular dislocation geometry and coseismic-slip distribution. We use a bootstrap approach to investigate uncertainties in the model parameters and define confidence bounds for all the inverted parameters. The rupture occurred on a N129°E striking and 50° southwestward dipping normal fault, in agreement with geological observations of surface breaks along the Paganica fault. Our distributed slip model exhibits a zone of relatively higher slip (〉60 cm) between ∼1.5 and ∼11 km depth, along a roughly downdip, NW–SE elongated patch, confined within the fault plane inverted assuming uniform-slip. The highest slip, of the order of ∼1 m, occurred on a ∼16 km2 area located at ∼5 km depth, SE of the mainshock epicentre. The analysis of model resolution suggests that slip at depth below ∼5 km can be resolved only at a spatial scale larger than 2 km, so a finer discretization of different asperities within the main patch of coseismic-slip is not allowed by GPS data. We compute the coseismic Coulomb stress changes in the crustal volume affected by the major aftershocks, and compare the results obtained from the uniform-slip and the heterogeneous-slip models. We find that most of the large aftershocks occurred in areas of Coulomb stress increase of 0.2–13 bar and that a deepening of the slip distribution down to a depth greater than 6 km in the SE part of the fault plane, in agreement with the inverted slip model, can explain the deepest, April 7, Mw 5.3 aftershock.
    Description: Published
    Description: 473-489
    Description: 1.9. Rete GPS nazionale
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: Satellite geodesy ; Space geodetic surveys ; Earthquake ground motions ; Earthquake source observations ; Earthquake interaction, forecasting, and prediction ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 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::04.06.02. Earthquake interactions and probability ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
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  • 63
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    The effect of directivity in PSHA framework (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We propose a method to introduce a refined representation of the ground motion in the framework of the Probabilistic Seismic Hazard Analysis (PSHA). This study is especially oriented to the incorporation of a priori information about source parameters, by focusing on the directivity effect and its influence on seismic hazard maps. Two strategies have been followed. One considers the seismic source as an extended source, and it is valid when the PSHA seismogenetic sources are represented as fault segments. We show that the incorporation of variables related to the directivity effect can lead to variations up to 30% of the hazard level, in terms of spectral acceleration response at 5 sec., exceeding probability of 10% in 50 years. The second one concerns the more general problem of the seismogenetic areas, where each point is a seismogenetic source having the same chance of enucleate a seismic event. In our proposition the point source is associated to the rupture-related parameters, defined using a statistical description. As an example, we consider a source point of an area characterized by strike slip faulting style. With the introduction of the directivity correction the modulation of the hazard map reaches values up to 100%. The introduction of directivity does not increase uniformly the hazard level, but acts more like a redistribution of the estimation that is consistent with the fault orientation. A general increase appears only when no a-priori information is available. However, nowadays good a-priori knowledge exists on style of faulting, dip and orientation of faults associated to the majority of the seismogenetic zones of the present seismic hazard maps. Following this method, all the information collected may be easily converted to obtain a more comprehensive and meaningful probabilistic Seismic Hazard formulation.
    Description: Published
    Description: 616-626
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: reserved
    Keywords: Earthquake ground motion ; Earthquake source observation ; Probabilistic Seismic Hazard ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
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  • 64
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    Microstructures of melt inclusions in anatectic metasedimentary (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: The occurrence of crystallized and glassy melt inclusions (MI) in high-grade, partially melted metapelites and metagraywackes has opened up new possibilities to investigate anatectic processes. The present study focuses on three case studies: khondalites from the Kerala Khondalite Belt (India), the Ronda migmatites (Spain), and the Barun Gneiss (Nepal Himalaya). The results of a detailed microstructural investigation are reported, along with some new microchemical data on the bulk composition of MI. These inclusions were trapped within peritectic garnet and ilmenite during crystal growth and are therefore primary inclusions. They are generally isometric and very small in size, mostly £15 lm, and only rarely reaching 30 lm; they occur in clusters. In most cases inclusions are crystallized ( nanogranites ) and contain a granitic phase assemblage with quartz, feldspar and one or two mica depending on the particular case study, commonly with accessory phases (mainly zircon, apatite, rutile). In many cases the polycrystalline aggregates that make up the nanogranites show igneous microstructures, e.g. granophyric intergrowths, micrographic quartz in K-feldspar and cuneiform rods of quartz in plagioclase. Further evidence for the former presence of melt within the investigated inclusions consists of melt pseudomorphs, similar to those recognized at larger scale in the host migmatites. Moreover, partially crystallized inclusions are locally abundant and together with very small (£8 lm) glassy inclusions may occur in the same clusters. Both crystallized and partially crystallized inclusions often display a diffuse nanoporosity, which may contain fluids, depending on the case study. After entrapment, inclusions underwent limited microstructural modifications, such as shape maturation, local necking down processes, and decrepitation (mainly in the Barun Gneiss), which did not influence their bulk composition. Re-homogenized nanogranites and glassy inclusions show a leucogranitic and peraluminous composition, consistent with the results of partial melting experiments on metapelites and metagraywackes. Anatectic MI should therefore be considered as a new and important opportunity to understand the partial melting processes.
    Description: Published
    Description: 303-322
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: JCR Journal
    Description: restricted
    Keywords: garnet ; melt inclusions ; melt microstructures ; migmatites ; nanogranite ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology
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  • 65
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    Ground deformation at calderas driven by fluid injection: modelling unrest episodes at Campi Flegrei (Italy) (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-03
    Description: Campi Flegrei collapse caldera (Italy) is a high-risk volcanic area located close to Naples and includes part of the densely populated city. This area is characterised by large up and down ground displacements. The last large uplift episode caused 3.5 m of cumulative vertical displacement at the centre of the town of Pozzuoli, during the period 1969–1984. Up and down ground movements in this area often occur without intercurring eruptions and are similar to what is observed at other calderas worldwide. Here, however, they appear more evident and amplified. Understanding the mechanism of such movements is crucial for hazard assessment and eruption forecast, mainly due to this densely populated area. This paper presents a detailed model for ground displacements due to deep fluid injection in shallower layers. Such a model explains in a natural way the occurrence of uplift and subsidence without eruptions. We show that it is possible to fit observed ground deformation in this area with a thermofluid dynamical model. The model obtained is also consistent with other observations like microgravity changes, changes in CO2 flux, etc. Here, we suggest that significant uplift and subsidence at calderas can be due to effects of deep fluid injections other than magma. At Campi Flegrei, however, a partial magmatic contribution at the origin of the observed episodes cannot be excluded.
    Description: Published
    Description: 833–847
    Description: JCR Journal
    Description: restricted
    Keywords: Numerical approximations and analysis; Hydrothermal systems; Explosive volcanism; Calderas ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous
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  • 66
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    Mantle viscosity inference: a comparison between Simulated Annealing and Neighbourhood Algorithm inversion methods (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Two direct search methods, simulated annealing and neighbourhood algorithm, are applied to the inversion of the viscosity profile of the mantle using relative sea level time-histories for the Hudson Bay region. In problems characterized by a low-dimensional model space (Nd = 2 in this study), the two inversion methods show comparable performances. When a larger number of dimensions is involved (specifically Nd = 6), we directly show that simulated annealing is less effective than neighbourhood algorithm in overcoming the obstacles that are found in the model space when our specific data set is employed. This study confirms that modifications of the conventional Monte Carlo inversion method, such as simulated annealing and neighbourhood algorithm, are viable tools to determine the viscosity profile of the mantle, which, until recently, has been mainly tackled by means of linearized techniques.
    Description: Published
    Description: 890-900
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: mantle viscosity ; simulated annealing ; neighbourhood algorithm ; postglacial rebound ; 04. Solid Earth::04.01. Earth Interior::04.01.03. Mantle and Core dynamics
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  • 67
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    Some insights on the occurrence of recent volcanic eruptions of Mount Etna volcano (Sicily, Italy) (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-03
    Description: In the first part of this work, we make use of two non-parametric statistical pattern recognition algorithms and a multiple regression analysis to analyse seismic clusters occur ring around Mount Etna, Italy. The aim is to determine if the onset of flank eruptions at Mount Etna is linked to variations in the regional seismicity at a timescale of few weeks. From the analysis, we find that the discrimination between clusters preceding flank eruptions and clusters not related in time to flank activity is mainly linked to the volume output of the previous flank eruption, in some cases together with the time elapsed from its end. Instead, we do not find any difference in the seismicity features characterizing different types of clusters, except for a very small contribution of the number of seismic events in the clusters. This result does not confirm the existence, suggested in the past, of a direct link between the regional state of stress at a timescale of few weeks and the occurrence of flank eruptions on Mount Etna volcano. On the contrary, the result suggests that a prominent role in the flank eruption occur rence is played by the re-charging of the feeding system. In the second part of this study we analyse the relationship between the magma volume erupted in an eruption and the interevent time following it, finding that a ‘time-predictable model’ satisfactorily describes the occurrence of eruptions at Mount Etna in the last decades. The latter analysis is car ried out both on the flank eruption catalogue only, and on the complete catalogue of flank and summit eruptions, with comparable results.
    Description: Published
    Description: 1203–1218
    Description: JCR Journal
    Description: restricted
    Keywords: flank eruptions ; Mount Etna volcano ; regional tectonic stress ; statistical pattern recognition ; time predictability ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
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  • 68
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    The Italian present-day stress map (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-03
    Description: In this paper, we present a significant update of the Italian present-day stress data compilation not only to improve the knowledge on the tectonic setting of the region or to constrain future geodynamic models, but also to understand the mechanics of processes linked to faulting and earthquakes. In this paper, we have analysed, revised and collected new contemporary stress data from borehole breakouts and we have assembled earthquake and fault data. In total, 206 new quality-ranked entries complete the definition of the horizontal stress orientation and tectonic regime in some areas, and bring new information mainly in Sicily and along the Apenninic belt. Now the global Italian data set consists of 715 data points, including 499 of A–C quality, representing an increase of 37 per cent compared to the previous compilation. The alignment of horizontal stresses measured in some regions, closely matches the ∼N–S first- order stress field orientation of ongoing relative crustal motions between Eurasia and Africa plates. The Apenninic belt shows a diffuse extensional stress regime indicating a ∼NE–SW direction of extension, that we interpret as related to a second-order stress field. The horizontal stress rotations observed in peculiar areas reflect a complex interaction between first-order stress field and local effects revealing the importance of the tectonic structure orientations. In particular, in Sicily the new data delineate a more complete tectonic picture evidencing adjacent areas characterized by distinct stress regime: northern offshore of Sicily and in the Hyblean plateau the alignment of horizontal stresses is consistent with the crustal motions, whereas different directions have been observed along the belt and foredeep.
    Description: Published
    Description: 705–716
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: Downhole methods; Seismicity and tectonics; Crustal structure; Europe. ; borehole breakouts, earthquakes, faults ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress
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  • 69
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    Magma chambers emplaced in carbonate substrate: petrogenesis of skarn and cumulate rocks and implication on CO2-degassing in volcanic areas (2012)
    Oxford University Press
    Details
    Publication Date: 2017-04-04
    Description: Crystal-rich lithic clasts occurring in volcanic deposits are key tools to understand processes of storage, cooling, and fractionation of magmas in pre-eruptive volcanic systems. These clasts, indeed, represent snapshots of the magma-chamber/host-rock interface before eruptions and provide information on crystallization, differentiation, and degrees of interaction between magma and wall-rocks. In this study, with the aim to shed light on magma-carbonate interaction and CO2 emission in volcanic areas, we focused on the petrology of cumulate and skarn rocks by using as case study a suite of mafic and calcite-bearing lithic clasts from the Colli Albani Volcanic District. By means of phase relations, bulk rock chemistry, phase compositions, and stable isotope data we have recognized different types of cumulates and skarns. Cumulates containing either clinopyroxene±olivine associated with Cr-bearing spinel or glass+phlogopite have been divided in primitive and differentiated, respectively. Primitive cumulates originate at the interface between a relatively primitive magma and carbonate-bearing rocks and show evidences of olivine instability (i.e. heteradcumulate texture) due to carbonate assimilation. Differentiated cumulates, characterized by Ca-rich olivines, phlogopite, and glass containing calcite, form from a differentiated magma in a system open to CaO-contamination. Skarns has been divided in exoskarns, characterized by xenomorphic texture and abundant calcite, and endoskarns, characterized by hypidiomorphic texture, Ca-Tschermak-rich mineral phases, and interstitial glass. Exoskarns formed by means of solid state reactions in a dolostone protolith whereas endoskarns crystallized at subliquidus temperature from a silicate melt that experienced exoskarns assimilation. Our study evidences that magma-carbonate interaction can not be considered a one step process exhausting just after the formation of skarn shells. Magma and carbonate rocks, when in contact, continuously interact leading to the formation of exoskarns, endoskarns, cumulates (primitive and differentiated ones), and differentiated melts. Finally, by means of oxygen and carbon isotope compositions of calcite in equilibrium with skarns, we demonstrate that carbonate assimilation represents a source of massive CO2 degassing mechanism due to the consumption of calcite and removing of CO2 during the decarbonation process.
    Description: Sapienza Universita' di Roma INGV-DPC [Project V 3.1, Colli Albani].
    Description: Published
    Description: 2307-2332
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: reserved
    Keywords: magma/carbonate interaction ; CO2 degassing ; c umulate and skarn ; Colli Albani ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology
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  • 70
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    Complexity of the rupture process during the 2009 L’Aquila, Italy, earthquake (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: In this study, we investigate the rupture history of the April 6th 2009 (Mw 6.1) L’Aquila normal faulting earthquake by using a nonlinear inversion of strong motion, GPS and DInSAR data. Both the separate and joint inversion solutions reveal a complex rupture process and a heterogeneous slip distribution. Slip is concentrated in two main asperities: a smaller shallow patch of slip located up-dip from the hypocenter and a second deeper and larger asperity located southeastward along strike direction. The key feature of the source process emerging from our inverted models concerns the rupture history, which is characterized by two distinct stages. The first stage begins with rupture nucleation and with up-dip propagation at relatively high (∼ 4.0 km/s), but still sub-shear, rupture velocity. The second stage starts nearly 2.0÷2.5 seconds after nucleation and it is characterized by the along strike rupture propagation. The largest and deeper asperity fails during this stage of the rupture process. The rupture velocity is larger in the up-dip than in the along-strike direction. The up-dip and along-strike rupture propagation are separated in time and associated with a Mode II and a Mode III crack, respectively. The comparison between the source models inferred in this study with the Poisson ratio anomalies in the crustal volume containing the fault plane (Di Stefano et al., 2011) allows the interpretation of the delay in along-strike rupture propagation in terms of a structural control of the rupture history. Our results show that the L’Aquila earthquake featured a very complex rupture, with strong spatial and temporal heterogeneities suggesting a strong frictional and/or structural control of the rupture process.
    Description: Published
    Description: 607-621
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: restricted
    Keywords: Inverse theory;Earthquake dynamics;Earthquake ground motions;Earthquake source observations;Body waves;Rheology and friction of fault zones ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous
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  • 71
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    Directional resonance variations across the Pernicana Fault, Mt Etna, in relation to brittle deformation fields (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: The Pernicana Fault (PF) is the main structural element of Mt Etna and the northern boundary of a section sliding to the southeast. Observed ground motion records in the damage zone of the PF show strong variations of directional resonance in the horizontal plane. The observed resonance directions exhibit an abrupt rotation of azimuth by about 30◦ across the fault, varying from N166◦ on the north side to N139◦ on the south. We interpret the directional resonance observations in terms of changes in the kinematics and deformation fields on the opposite sides of the fault. The northern side is affected primarily by the left-lateral strike-slip movement, whereas the southern side, that is subjected also to sliding, is under a dominant extensional stress regime. Brittle deformation models based on the observed kinematic field predict different sets of fractures on the opposite sides of the fault: synthetic cleavages and extensional fractures are expected to dominate in the northern and southern sides, respectively. These two fracture fields have different orientations (N74◦ and N42◦, respectively) and both show a near-orthogonal relation (∼88◦ in the northern sector and ∼83◦ to the south) with the azimuth of the observed directional resonance. We conclude that the direction of the largest resonance motions is sensitive to and has transversal relationship with the dominant fracture orientation. The directional amplification is inferred to be produced by stiffness anisotropy of the fault damage zone, with larger seismic motions normal to the fractures.
    Description: Published
    Description: 986–996
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake ground motions; Site effects; Wave propagation ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
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  • 72
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    Assessing annual global M6+ seismicity forecasts (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We consider a seismicity forecast experiment conducted during the last 4 yr. At the beginning of each year, three models make a 1-yr forecast of the distribution of large earthquakes everywhere on the Earth. The forecasts are generated and the observations are collected in the Collaboratory for the Study of Earthquake Predictability (CSEP). We apply CSEP likelihood measures of consistency and comparison to see how well the forecasts match the observations, and we compare results from some intuitive reference models. These results illustrate some undesirable properties of the consistency tests: the tests can be extremely sensitive to only a few earthquakes, and yet insensitive to seemingly obvious flaws—a na ̈ıve hypothesis that large earthquakes are equally likely everywhere is not always rejected. The results also suggest that one should check the assumptions of the so-called T and W comparison tests, and we illustrate some methods to do so. As an extension of model assessment, we explore strategies to combine forecasts, and we discuss the implications for operational earthquake forecasting. Finally, we make suggestions for the next generation of global seismicity forecast experiments.
    Description: Published
    Description: 422-431
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: probabilistic forecasting ; statistical seismology ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability
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  • 73
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    The hydrological signature of a seismogenic source: coseismic hydrological changes in response to the 1915 Fucino (Central Italy) earthquake (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: The M ∼ 7 1915 Fucino (Central Italy) earthquake represents one of the most destructive seismic events ever occurred in the Italian Peninsula. Several seismogenic faults have been proposed in the past decades as the source of the earthquake by means of different approaches and techniques that lead to a variety of speculations about the source mechanism and the fault location, often contrasting with one another. The 1915 earthquake produced a remarkable data set of 73 coseismic hydrological changes in the near and intermediate field that consist in variation of the flow of streams and springs, liquefaction, rise of water temperature and turbidity. In this paper, we study the coseismic water level changes induced by the 1915 earthquake in the near field to provide convincing clues on the geometry of the earthquake causative fault. We model the coseismic strain field induced by seventeen individual faults proposed through different approaches, and compare its pattern with the distribution of streamflow changes. We find: (i) clues on the most probable geometry of the earthquake causative fault. Best fits between modelled deformation and observed data are displayed by sources (derived by geological or seismological data) that share several distinctive features, as they are ∼135◦-striking, SW-dipping, 25–30-km-long normal faults located along the eastern side of the Fucino basin. These data point to the Serrone Fault and the Parasano Fault as the most likely causative structures and support the hypothesis that the coseismic ruptures observed in the field represented primary surface faulting. On the contrary, our calculations show that the Pescina Fault and the Ventrino Fault are secondary faults from the perspective of the hydrological response. Finally, one of the best scoring potential sources (from geological data) is a multifaulting system that considers the presence, in the central-western part of the basin, of fault splays synthetic and antithetic to the main seismogenic structures; therefore, we infer for these splays a possible active involvement in a 1915-like seismogenic process; (ii) evidence against a number of seismogenic structures that were previously associated with the earthquake. In particular, the plots of coseismic strain induced by sources uniquely derived by macroseismic or geodetic data prove to be inconsistent with the polarities of the hydrological signatures. Also, sources mainly characterized by reverse faulting and/or by right-lateral strike-slip component are discarded and (iii) as a final remark, we maintain that the study of the hydrological signatures of earthquake strain can offer an alternative tool in the investigation of the historical seismicity, to estimate the focal mechanism of major earthquakes capable of giving rise to a consistent data set of hydrological data.
    Description: Published
    Description: 1374-1388
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: 1915 Fucino earthquake ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous
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    Discriminating among distinct source models of the 1908 Messina Straits earthquake by modelling intensity data through full wavefield seismograms (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Macroseismic intensities are the only available data for most historical earthquakes and often represent the unique source of information for crucial events in the definition of seismic hazard. In this paper, we attempt at getting insight into source characteristics by reproducing the observed intensity field. As a test case, we study the source of 1908 Messina Straits earthquake ( M W = 7.1), by testing three distinct fault models deduced from the analysis of geodeticdata.Startingfromthestaticslipdistribution,wedevelop kinematicsourcemodelsfor the investigated fault and compute full waveform synthetic seismograms in a 1-D structural model, also accounting for anelastic attenuation. Then, we convert both computed peak- ground acceleration (PGA) and peak-ground velocity (PGV) to macroseismic intensity at 100 selected sites, by means of specific empirical relations for the Italian region. By comparing the original data separately with PGA- and PGV-based intensity fields, we discriminate among the tested faults and determine the best values for the investigated kinematic parameters of the source. We also perform a misfit analysis for the best source model, in order to investigate the dependence of the results on the selected parametrization. The results of the analysis indicate that among the tested models, the one characterized by an east-dipping fault, with strike- oriented NS slightly rotated clockwise, better explains the observed macroseismic field of the 1908 Messina Straits earthquake. Besides, the fracture nucleated at the southern end of the fault and ruptured northward, producing considerable directivity effects. This is in agreement with the published results obtained from the investigation of the historical seismograms. We alsodeterminerealisticvalues fortherupturevelocityand therise-time.Ourstudyconfirms the greatpotentialofthemacroseismicdata,demonstratingthattheycontainenoughinformationto constrain important characteristics of the fault, which can be retrieved by using complex source models and computing complete wavefield. Moreover, we also show that the simultaneous comparison of both PGA- and PGV-based synthetic macroseismic fields with the original intensities provides tighter constraints for discriminating among different source models, with respect to what attainable from each of them
    Description: Published
    Description: 164-173
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake ground motions; Earthquake source observations. ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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    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-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We analyzed a broad region around L’Aquila in search of seismogenic faults similar to that responsible for the 6 April 2009 earthquake (Mw 6.3). Having the lessons learned from this earthquake in mind, we focused on adjacent areas displaying similar morphotectonic, geological and structural evidence. The basin running from Barisciano to Civitaretenga-Navelli, notably located near the southeastern edge of the 2009 aftershock pattern, appears to be one of such areas. We collected morphotectonic and structural data indicating that this basin is underlain by a major active normal fault (San Pio Fault). All the observations are very much reminiscent of the morphotectonic, geological and structural setting of area struck by the L’Aquila earthquake, suggesting that the newly identified fault has the potential for a Mw 6.2-6.4 shock.
    Description: Published
    Description: Pages: 108–115
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: partially_open
    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
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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    Horizontal polarization of ground motion in the Hayward fault zone (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We investigate shear wave polarization in the Hayward fault zone near Niles Canyon, Fremont, CA. Waveforms of 12 earthquakes recorded by a seven-accelerometer seismic array around the fault are analysed to clarify directional site effects in the fault damage zone. The analysis is performed in the frequency domain through H/V spectral ratios with horizontal components rotated from 0◦ to 180◦, and in the time domain using the eigenvectors and eigenvalues of the covariance matrix method employing three component records. The near-fault ground motion tends to be polarized in the horizontal plane. At two on-fault stations where the local strike is N160◦, ground motion polarization is oriented N88 ± 19◦ and N83 ± 32◦, respectively. At a third on-fault station, the motion is more complex with horizontal polarization varying in different frequency bands. However, a polarization of N86 ± 7◦, similar to the results at the other two on-fault stations, is found in the frequency band 6–8 Hz. The predominantly high-angle polarization from the fault strike at the Hayward Fault is consistent with similar results at the Parkfield section of the San Andreas Fault and the Val d’Agri area (a Quaternary extensional basin) in Italy. In all these cases, comparisons of the observed polarization directions with models of fracture orientation based on the fault movement indicate that the dominant horizontal polarization is near-orthogonal to the orientation of the expected predominant cracking direction. The results help to develop improved connections between fault mechanics and near-fault ground motion.
    Description: Published
    Description: 1255–1272
    Description: JCR Journal
    Description: open
    Keywords: Earthquake ground motions. ; Interface waves ; Site effects ; Wave propagation ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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    Land subsidence along the Ionian coast of SE Sicily (Italy), detection and analysis via Small Baseline Subset (SBAS) multitemporal differential SAR interferometry (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We present the results of a multi-temporal, differential interferometric synthetic aperture radar (DInSAR) analysis aiming to identify active surface deformation phenomena in southeastern Sicily. The study area has been chosen because of its strong seismicity, high concentration of industrial and agricultural activities, and high density of people living in the coastal area. Furthermore, the morphology, lithology and climatic feature of this sector of the Hyblean foreland are suitable for an interferometric analysis, providing a high coherence over the area. We used the Small BAseline Subset (SBAS) multitemporal DInSAR technique from Berardino et al., 2002, to calculate mean ground velocity maps and displacement time series from a large data set of European Remote Sensing Satellites (ERS 1-2) images spanning the time period 1992-2000. The reliability of the DInSAR results was tested calculating the EastSAR and UpSAR values over two permanent global positioning system (GPS) stations in the area, and comparing them with the EastGPS and UpGPS values. The residuals between GPS and DInSAR velocities were 1 and 0.6 mm/yr for the Up and East components, respectively. Four main subsiding areas, previously undetected, have been identified, in correspondence of the towns of Augusta, Siracusa, Priolo, and Villasmundo. The observed deformation phenomena are located within coastal structural basins, filled with Pleistocene and Holocence deposits, except the Villasmundo land subsidence which is located on the Hyblean plateau. The measured deformation rates reach values up to -18 mm/yr in Augusta, -6 mm/yr in Siracusa, -5 mm/yr in Villasmundo and -4.5 mm/yr in Priolo. The examination of velocity profiles, time series, and geological data allows us to relate all the detected deformation patterns primarily to groundwater over-exploitation. A multi-dimensional interpolation with kriging was performed to obtain a field subsidence map. A first order elastic deformation model was used to simulate the peculiar features of the Villasmundo subsidence
    Description: ASI-SIGRIS project. ESA Cat1 3769. MIUR Fondo per il sostegno dei giovani.
    Description: Published
    Description: 273-286
    Description: 1.10. TTC - Telerilevamento
    Description: JCR Journal
    Description: partially_open
    Keywords: subsidence ; InSAR ; 05. General::05.08. Risk::05.08.02. Hydrogeological risk
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    Earthquake sequences of the last millennium in L'Aquila and surrounding regions (central Italy) (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We have analysed the history of seismic activity in the region of L'Aquila to compare the 2009 sequence with previous ones. Historical catalogues are exhaustive for large shocks, but not for small earthquakes and swarms. Our original compilation highlights repeated seismic sequences from 1315 ad to present. In the 20th century, at least 23 sequences affected the Abruzzi region, 8 of which were very close to L'Aquila. In previous centuries, we found evidence of at least 13 sequences around L'Aquila, with maximum magnitude ∼4 to ∼5. Only three sequences were followed by stronger shocks (1461, 1703 and 2009). However, many strong events of the region (1349, 1762, 1915, 1950) were not preceded by foreshocks. We describe here the last of these sequences (1985) showing its strong similarity with the 2009 one, except its final evolution (no large event in 1985). Our analysis suggests that seismic sequences alone cannot be considered straight forerunners of incoming strong events.
    Description: Published
    Description: 52–61
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: L’Aquila earthquake ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
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    Dissolved gases in brackish thermal waters: an improved analytical method (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: An improved method based on equilibrium partitioning between water samples and an inert host gas, introduced after sampling, is proposed for determining multiple species of dissolved gases in brackish water. The method itself, and the most convenient equations for describing gas solubilities in brackish waters, is described in detail. The method allows the rapid characterization of several sites and represents a useful tool for geochemical surveys. A comparison between replicate samples analyzed using different procedures demonstrates the efficiency of the method and indicates that the abundances of the main dissolved gases can be obtained, which can then be used to determine underlying geochemical processes. A Microsoft Excel worksheet is provided to easily calculate the concentration of dissolved gas species.
    Description: Published
    Description: 236-244
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: JCR Journal
    Description: restricted
    Keywords: brackish thermal waters ; dissolved gases ; 03. Hydrosphere::03.03. Physical::03.03.01. Air/water/earth interactions
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    Isostatic rebound following the Alpine deglaciation: impact on the sealevel variations and vertical movements in the Mediterranean region (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: The present-day sea level variations and geodetically observed ground deformations in the Mediterranean area are normally ascribed to the combined effect of tectonic or human-driven subsidence and postglacial uplift as a result of the melting of the major Pleistocene ice sheets. However, another potential cause of deformation, only marginally considered to date, is the melting of the glacier that covered the Alps during the last glacial maximum (LGM). The aim of this paper is to predict the long-term sea level variations induced by the melting of both the late-Pleistocene and Alpine ice sheets and compare our results with the relative sea level (RSL) observations available in the Mediterranean region. This task is accomplished solving the sea level equation (SLE) for a spherically symmetric viscoelastic Earth. Our analysis shows that the melting of the Alpine glacier has marginally affected the Holocene sea level variations in the near-field sites in southern France (Marseilles and Roussillon) and the central Tyrrhenian sea (Civitavecchia), and that the RSL predictions are significantly sensitive to the chronology of the remote ice aggregates. The computations, which are performed using a specific mantle viscosity profile consistent with global observations of RSL rise, show that the uplift rate driven by the Alpine isostatic readjustment may account for up to 1/3 of the rates observed at GPS stations in the western portion of the chain. Our results suggest that a thorough modelization of both near- and far-field ice sheets is necessary to gain a better insight into the present-day deformations and sea level variations in the Mediterranean region.
    Description: Published
    Description: 137-147
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Alpine glacier ; glacial rebound ; mantle viscosity ; sea level variations ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
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    Stress-induced temperature variations in groundwater of the Monferrato area (north-western Italy) (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Although characterized by low seismicity, the Monferrato area of north-western Italy was affected by earthquakes, of magnitude M5.1 and M4.8, in 2000 and 2001. At the same time, marked changes were recorded in water temperature and chemistry in several wells within the epicentral area. In May 2004, an automatic network for the continuous monitoring of groundwater was installed in selected wells to study the phenomenon. Here, we report on data collected during a 3-year period of groundwater monitoring. During the first year, episodes of water heating (by up to 20°C) were observed in one monitored well. The temporal analysis of the seismic activity recorded in the area revealed as almost all seismic events occurred during the period of elevated water temperatures. The similar timing of earthquakes and groundwater-temperature anomalies suggests that both may be triggered by the same processes acting in the crust.
    Description: Published
    Description: 142-149
    Description: JCR Journal
    Description: reserved
    Keywords: groundwater monitoring ; pore fluid pressure; ; tectonic stress ; 03. Hydrosphere::03.02. Hydrology::03.02.02. Hydrological processes: interaction, transport, dynamics ; 03. Hydrosphere::03.02. Hydrology::03.02.04. Measurements and monitoring
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    Joint observation of coherent coda waves at surface and underground arrays (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Local and regional seismicity jointly recorded by two dense small aperture arrays, one installed at surface and one at 1.3 km depth, constitutes an interesting data set useful for coda observations. Applying array techniques to earthquakes recorded at the two arrays we measure slowness, backazimuth and correlation coefficient of the coherent coda wave signals in five frequency bands in the range 1–10 Hz. Slowness distributions show marked differences between surface and underground, with slow signals at surface (slowness greater than 1.0 s km−1) that are not observed underground. We interpret these coherent signals as surface waves produced by the interaction of body waves with the free surface characterized by rough topography. The backazimuth values measured in the frequency bands centred at 1.5 and 3 Hz are almost uniformly distributed between 0 and 360◦, while those measured at higher frequencies show different distributions between surface and underground. On the contrary, the earthquake envelopes show very similar coda shapes between surface and underground recordings, with an almost constant coda-amplitude ratio (between 4 and 8) in a wide frequency range.
    Description: Published
    Description: 367-371
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: JCR Journal
    Description: restricted
    Keywords: Coda waves ; Wave scattering and diffraction ; Wave propagation ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
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    Spatial distribution of intrinsic and scattering seismic attenuation in active volcanic islands – II: Deception Island images (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: In this work, we present regional maps of the inverse intrinsic quality factor (Qi −1), the inverse scattering quality factor (Qs −1) and total inverse quality factor (Qt −1) for the volcanic environment of Deception Island (Antarctica). Our attenuation study is based on diffusion approximation, which permits us to obtain the attenuation coefficients for every single couple source-receiver separately. The data set used in this research is derived from an active seismic experiment using more than 5200 offshore shots (air guns) recorded at 32 onshore seismic stations and four ocean bottom seismometers. To arrive at a regional distribution of these values, we used a new mapping technique based on a Gaussian space probability function. This approach led us to create ‘2-D probabilistic maps’ of values of intrinsic and scattering seismic attenuation. The 2-D tomographic images confirm the existence of a high attenuation body below an inner bay of Deception Island. This structure, previously observed in 2-D and 3-D velocity tomography of the region, is associated with a massive magma reservoir. Magnetotelluric studies reach a similar interpretation of this strong anomaly. Additionally, we observed areas with lower attenuation effects that bear correlation with consolidated structures described in other studies and associated with the crystalline basement of the area. Our calculations of the transport mean-free path and absorption length for intrinsic attenuation gave respective values of ≈950 m and 5 km, which are lower than the values obtained in tectonic regions or volcanic areas such as Tenerife Island. However, as observed in other volcanic regions, our results indicate that scattering effects dominate strongly over the intrinsic attenuation.
    Description: This work has been partially supported by the Spanish project Ephestos, CGL2011–29499-C02–01, by the EU project EC-FP7 MEDiterranean SUpersite Volcanoes (MED-SUV), by the Basque Government researcher training program BFI09.277 and by the Regional project ‘Grupo de Investigaci´on en Geof´ısica y Sismolog´ıa de la Junta de Andaluc´ıa, RNM104.’ Edoardo del Pezzo was partly supported by DPC-INGV projects UNREST SPEED and V2 (Precursori).
    Description: Published
    Description: 1957-1969
    Description: 3.1. Fisica dei terremoti
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: restricted
    Keywords: Seismic attenuation; ; Seismic tomography ; Volcano seismology ; Wave scattering and diffraction ; Wave propagation ; 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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    The stress field in Europe: optimal orientations with confidence limits (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: This article has been accepted for publication in Geophysical Journal International ©: The Authors 2003. Published by Oxford University Press on behalf of The Royal Astronomical Society. All rights reserved.
    Description: In this study, we modify and extend a data analysis technique to determine the stress orientations between data clusters by adding an additional constraint governing the probability algorithm. We apply this technique to produce a map of the maximum horizontal compressive stress (S_Hmax) orientations in the greater European region (including Europe, Turkey and Mediterranean Africa). Using the World Stress Map dataset release 2008, we obtain analytical probability distributions of the directional differences as a function of the angular distance, θ. We then multiply the probability distributions that are based on pre-averaged data within θ〈3° of the interpolation point and determine the maximum likelihood estimate of the S_Hmax orientation. At a given distance, the probability of obtaining a particular discrepancy decreases exponentially with discrepancy. By exploiting this feature observed in the World Stress Map release 2008 dataset, we increase the robustness of our S_Hmax determinations. For a reliable determination of the most likely S_Hmax orientation, we require that 90% confidence limits be less than ±60° and a minimum of three clusters, which is achieved for 57% of the study area, with small uncertainties of less than ±10° for 7% of the area. When the data density exceeds 0.8×10^-3 data/km2, our method provides a means of reproducing significant local patterns in the stress field. Several mountain ranges in the Mediterranean display 90° changes in the S_Hmax orientation from their crests (which often experience normal faulting) and their foothills (which often experience thrust faulting). This pattern constrains the tectonic stresses to a magnitude similar to that of the topographic stresses.
    Description: This work was supported by the DPC-INGV 2008-2010 S1 project, the EU-FP7 project “Seismic Hazard Harmonization in Europe” (SHARE; Grant agreement no. 226967), and project MIUR-FIRB "Abruzzo" (code: RBAP10ZC8K_003).
    Description: Published
    Description: 3.1. Fisica dei terremoti
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: 4.2. TTC - Modelli per la stima della pericolosità sismica a scala nazionale
    Description: JCR Journal
    Description: partially_open
    Keywords: Neotectonics ; Seismicity and tectonics ; Fractures and faults ; Intra-plate processes ; Plate motions ; Dynamics: gravity and tectonics ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 05. General::05.02. Data dissemination::05.02.99. General or miscellaneous
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    Location and magnitudes of earthquakes in Central Asia from seismic intensity data: model calibration and validation (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: macroseismic intensity data. A set of 2373 intensity observations from 15 earthquakes is analysed to calibrate non-parametric models for the source and attenuation with distance, the distance being computed from the instrumental epicentres located according to the International Seismological Centre (ISC) catalogue. In a second step, the non-parametric source model is regressed against different magnitude values (e.g. MLH, mb, MS, Mw) as listed in various instrumental catalogues. The reliability of the calibrated model is then assessed by applying the methodology to macroseismic intensity data from 29 validation earthquakes for which bothMLH and mb are available from the Central Asian Seismic Risk Initiative (CASRI) project and the ISC catalogue. An overall agreement is found for both the location and magnitude of these events, with the distribution of the differences between instrumental and intensity-based magnitudes having almost a zero mean, and standard deviations equal to 0.30 and 0.44 for mb and MLH, respectively. The largest discrepancies are observed for the location of the 1985, MLH = 7.0 southern Xinjiang earthquake, whose location is outside the area covered by the intensity assignments, and for the magnitude of the 1974, mb = 6.2 Markansu earthquake, which shows a difference in magnitude greater than one unit in terms of MLH. Finally, the relationships calibrated for the non-parametric source model are applied to assign different magnitude-scale values to earthquakes that lack instrumental information. In particular, an intensity-based moment magnitude is assigned to all of the validation earthquakes.
    Description: Published
    Description: 710-724
    Description: 5.1. TTC - Banche dati e metodi macrosismici
    Description: JCR Journal
    Description: restricted
    Keywords: seismicity and tectonics: seismic attenuarion; Asia ; 04. Solid Earth::04.06. Seismology::04.06.05. Historical seismology
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    Strain rate relaxation of normal and thrust faults in Italy (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We find that geodetic strain rate (SR) integrated with the knowledge of active faults points out that hazardous seismic areas are those with lower SR, where active faults are possibly approaching the end of seismic cycle. SR values estimated from GPS velocities at epicentral areas of large historical earthquakes in Italy decrease with increasing elapsed time, thus highlighting faults more prone to reactivation. We have modelled an exponential decrease relationship between SR and the time elapsed since the last largest earthquake, differencing historical earthquakes according to their fault rupture style. Then, we have estimated the characteristic times of relaxation by a non-linear inversion, showing that events with thrust mechanism exhibit a characteristic time (∼ 990 yr) about three times larger than those with normal mechanism. Assuming standard rigidity and viscosity values we can infer an average recurrence time of about 600 yr for normal faults and about 2000 yr for thrust faults.
    Description: Published
    Description: 815-820
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: Seismic cycle ; Seismicity and tectonics ; Transient deformation ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
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    A comparison among general orthogonal regression methods applied to earthquake magnitude conversions (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Until a decade ago, regression analyses for conversions between different types of magnitude were using only the ordinary least squares method,which assumes that the independent variable is error free, or the simple orthogonal regression method,which assumes equal uncertainties for the two variables. The recent literature became aware of the inadequacy of such approaches and proposes the use of general orthogonal regression methods that account for different uncertainties of the two regression variables. Under the common assumption that only the variance ratio η between the dependent and independent variables is known, we compared three of such general orthogonal regression methods that have been applied to magnitude conversions: the chi-square regression, the general orthogonal regression, and the weighted total least squares. Although their formulations might appear quite different, we show that, under appropriate conditions, they all compute almost exactly the same regression coefficients and very similar (albeit slightly different) formal uncertainties. The latter are in most cases smaller than those estimated by bootstrap simulation but the amount of the deviation depends on the data set and on the assumed variance ratio.
    Description: European Union project SHARE (Seismic Hazard Harmonization in Europe) within the ambit of Task 3.1‘European Earthquake Database’.
    Description: Published
    Description: 1135-1151
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake source observations; Statistical seismology ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
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    Volcanic hot spot detection from optical multispectral remote sensing data using artificial neural networks (2014)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: This paper describes an application of artificial neural networks for the recognition of volcanic lava flow hot spots using remote sensing data. Satellite remote sensing is a very effective and safe way to monitor volcanic eruptions in order to safeguard the environment and the people affected by such natural hazards. Neural networks are an effective and well-established technique for the classification of satellite images. In addition, once well trained, they prove to be very fast in the application stage. In our study a back propagation neural network was used for the recognition of thermal anomalies affecting hot lava pixels. The network was trained using the three thermal channels of the Advanced Very High Resolution Radiometer (AVHRR) sensor as inputs and the corre- sponding values of heat flux, estimated using a two thermal component model, as reference outputs. As a case study the volcano Etna (Eastern Sicily, Italy) was chosen, and in particular the effusive eruption which took place during the month of 2006 July. The neural network was trained with a time-series of 15 images (12 nighttime images and 3 daytime images) and validated on three independent data sets of AVHRR images of the same eruption and on two relative to an eruption occurred the following month. While for both nighttime and daytime validation images the neural network identified the image pixels affected by hot lava with a 100 per cent success rate, for the daytime images also adjacent pixels were included, apparently not interested by lava flow. Despite these performance differences under different illumination conditions, the proposed method can be considered effective both in terms of classification accuracy and generalization capability. In particular our approach proved to be robust in the rejection of false positives, often corresponding to noisy or cloudy pixels, whose presence in multispectral images can often undermine the performance of traditional classification algorithms. Future work shall address application of the proposed method to data acquired with a high temporal resolution, such as those provided by the spinning enhanced visible and infrared imager sensor on board the Meteosat second generation geostationary satellite.
    Description: Published
    Description: 1525-1535
    Description: 5V. Sorveglianza vulcanica ed emergenze
    Description: JCR Journal
    Description: restricted
    Keywords: Image processing ; Neural networks ; fuzzy logic ; Remote sensing of volcanoes ; Hot-spot detection ; Mt. Etna ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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    Decarbonation and thermal microcracking under magmatic P-T-fCO2 conditions: the role of skarn substrata in promoting volcanic instability (2014)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We present a systematic study on the influence of pressure (0.1–600 MPa), temperature (750– 1200 ◦C), carbon dioxide fugacity (logfCO2 = −4.41 to 3.60) and time (2–12 hr) on the chemical and physical properties of carbonate rock. Our experiments aim to reproduce the conditions at the periphery of magma chamber where carbonate host rock is influenced by, but not readily assimilated by, magma. This permits the investigation of the natural conditions at which circulating fluids/gases promote infiltration reactions typical of metasomatic skarns that can involve large volumes of subvolcanic carbonate basements. Results show that, providing that carbon dioxide is retained in the pore space, decarbonation does not proceed at any magmatic pressure and temperature. However, when the carbon dioxide is free to escape, decarbonation can occur rapidly and is not hindered by a low initial porosity or permeability. Together with carbon dioxide and lime, portlandite, a mineral commonly found in voluminous metasomatic skarns, readily forms during carbonate decomposition. Post-experimental analyses highlight that thermal microcracking, a result of the highly anisotropic thermal expansion of calcite, exerts a greater influence on rock physical properties (porosity, ultrasonic wave velocities and elastic moduli) than decarbonation. Our data suggest that this will be especially true at the margins of dykes or magma bodies, where temperatures can reach up to 1200 ◦C. However, rock compressive strength is significantly reduced by both thermal cracking and decarbonation, explained by the relative weakness of lime + portlandite compared to calcite, and an increase in grain size with increasing temperature. Metasomatic skarns, whose petrogenetic reactions may involve a few tens of cubic kilometres, could therefore represent an important source of volcanic instability.
    Description: Published
    Description: 369-380
    Description: 2R. Laboratori sperimentali e analitici
    Description: JCR Journal
    Description: restricted
    Keywords: Volcanic hazards and risks ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 90
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    An experiment of muon radiography atMt Etna (Italy) (2014)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Interactions of conduit geometry with gas–liquid flows control volcanic activity, implying that the evaluation of volcanic hazards requires quantitative understanding of the inner structure of the volcano. The more established geophysical imaging techniques suffer from inherent ambiguity, may require spatially dense measurements in active areas and may not provide sufficient spatial resolution in the uppermost part of the conduit system. It is thus desirable to develop new imaging techniques allowing a better spatial resolution of a volcano's upper feeding system, with reduced ambiguity and a low level of risk for operators. Muon particles can be utilized to image the internal density distribution of volcanic structures. The principle of muon radiography is essentially the same as X-ray radiography, except for substituting penetrating particles in place of photons. Muons are more attenuated by higher density parts inside the target and thus information about its inner structure are obtained from the differential muon absorption. We report on a muon-imaging experiment that was conducted at Mt Etna in 2010. The target structure was one of the summit craters of the volcano. This experiment was performed using a muon telescope suitably designed to withstand the harsh conditions in the summit zone of a high volcano. We found a marked difference between synthetic and observed attenuation of muons through the target. This discrepancy is likely due to the bias on the observed flux, arising from false muon tracks. They are caused by low-energy particles that, by chance, hit simultaneously the two matrixes of the telescope, leading to detection of a false positive. We separated the useful from the unwanted signal through a first-order model of the background noise. The resulting signal is compared with the corresponding synthetic flux. Eventually, we found regions of higher- and lower-than-expected muon flux, that are possibly related to inner features of the target crater.
    Description: Published
    Description: 633-643
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Tomography; Volcano monitoring; Volcanic hazards and risks ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 91
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    Numerical evidences enabling to reconcile gravity and height changes in volcanic areas (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Gravity and height changes, reflecting magma accumulation in subsurface chambers, are evaluated using Finite Element models in order to resolve controversial relationships observed in some volcanic areas. When significant gravity changes occur without any significant deformation, or vice versa, it is often difficult, if not impossible, to jointly explain the observations using the popular Mogi model. Here we explore whether these discrepancies can be explained by magma compressibility and source geometry effects. Compression of resident magma and expansion of the chamber wall act concurrently to accommodate newly added magma. Gravity-height ratios are found to mainly depend on: (i) geometry of the sources, which control the volume expansion of the chamber, (ii) magma compressibility, which affects the contraction of the magma resident in the chamber, and (iii) depth of the sources. Our numerical results show that, when magma compressibility and non-spherical sources are taken into account, significant gravity variations can, indeed, be successfully reconciled with negligible height changes. This may be the case at Etna volcano, where gravity changes (about 40 miuGal) without any significant deformation (below 5 cm) were observed during the 1994-1995 inflation period. The numerical results point to the accumulation of a 1.4x10^10 kg mass into an elongated source simulating a shallow storage region supplying the summit craters.
    Description: Published
    Description: 164-173
    Description: 4V. Vulcani e ambiente
    Description: JCR Journal
    Description: restricted
    Keywords: numerical modeling, gravity and height changes ; 04. Solid Earth::04.03. Geodesy::04.03.05. Gravity variations
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  • 92
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    On the present-day crustal stress, strain-rate fields and mantle anisotropy pattern of Italy (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We present an up-to-date high resolution picture of the ongoing crustal deformation field of Italy, based on an extensive combination of permanent and non-permanent GPS observations carried out since 1994. In addition, we present an updated map of contemporary SHmax orientations computed by a multidisciplinary data set of well-constrained stress indicators, including both published results and novel analyses. The comparison of stress and geodetic strain-rates directions reveals that both patterns are near-parallel over a large part of the investigated area, highlighting that crustal stress and surface deformation are driven by the same mechanism. The comparison of the azimuthal patterns of surface strain and mantle deformation shows a modest correlation on the Alps and a low correlation along the Apennines chain and the Calabro-Peloritan Arc. Along the Apennines chain, this feature suggests the occurrence of significant strain partitioning and crust–mantle mechanical decoupling. Along the Calabro-Peloritan Arc, the apparent low correlation reflects a different mantle–crust mechanism of deformation to the ongoing subduction and rollback of the Ionian slab. In addition, the superposition of regional/local effects related to second-order sources (crustal lateral density changes, strength contrasts), which at regional/local scale modulate the crustal stress/strain-rate pattern, cannot be ruled out.
    Description: Published
    Description: 969-985
    Description: 1T. Geodinamica e interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Plate motions ; Seismic anisotropy ; Kinematics of crustal and mantle deformation ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 93
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    Seismic Q estimates in Umbria-Marche (central Italy): hints for the retrieval of a new attenuation law for seismic risk (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: In the Umbria Marche (Central Italy) region an important earthquake sequence occurred in 1997, characterized by nine earthquakes with magnitudes in the range between 5 and 6, that caused important damages and causalities. In the present paper we separately estimate intrinsic- and scattering- Q −1 parameters, using the classical MLTWA approach in the assumption of a half space model. The results clearly show that the attenuation parameters Qi −1 and Qs −1 are frequency dependent. This estimate is compared with other attenuation studies carried out in the same area, and with all the other MLTWA estimates obtained till now in other tectonic environments in the Earth. The bias introduced by the half space assumption is investigated through numerical solutions of the Energy Transport equation in the more realistic assumption of a heterogeneous crust overlying a transparent mantle, with a Moho located at a depth ranging between 35 and 45 km below the surface. The bias introduced by the half space assumption is significant only at high frequency. We finally show how the attenuation estimates, calculated with different techniques, lead to different PGA decay with distance relationships, using the well known and well proven Boore’s method. This last result indicates that care must be used in selecting the correct estimate of the attenuation parameters for seismic risk purposes. We also discuss the reason why MLTWA may be chosen among all the other available techniques, due to its intrinsic stability, to obtain the right attenuation parameters.
    Description: Published
    Description: 1370-1382
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: open
    Keywords: Seismic attenuation ; scattering ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 94
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    The seismogenic structure of the 2013–2014 Matese seismic sequence, Southern Italy: implication for the geometry of the Apennines active extensional belt (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Seismological, geological and geodetic data have been integrated to characterize the seismogenic structure of the late 2013-early 2014 moderate energy (maximum local magnitude MLmax = 4.9) seismic sequence that struck the interior of the Matese Massif, part of the Southern Apennines active extensional belt. The sequence, heralded by a ML = 2.7 foreshock, was characterized by two main shocks with ML = 4.9 and ML = 4.2, respectively, which occurred at a depth of ∼17–18 km. The sequence was confined in the 10–20 km depth range, significantly deeper than the 1997–1998 sequence which occurred few km away on the northeastern side of the massif above ∼15 km depth. The depth distribution of the 2013–14 sequence is almost continuous, albeit a deeper (16–19 km) and a shallower (11–15 km) group of events can be distinguished, the former including the main shocks and the foreshock. The epicentral distribution formed a ∼10 km long NNW–SSE trending alignment, which almost parallels the surface trace of late Pliocene–Quaternary southwest-dipping normal faults with a poor evidence of current geological and geodetic deformation. We built an upper crustal model profile for the eastern Matese massif through integration of geological data, oil exploration well logs and seismic tomographic images. Projection of hypocentres on the profile suggests that the seismogenic volume falls mostly within the crystalline crust and subordinately within the Mesozoic sedimentary cover of Apulia, the underthrust foreland of the Southern Apennines fold and thrust belt. Geological data and the regional macroseismic field of the sequence suggest that the southwest-dipping nodal plane of the main shocks represents the rupture surface that we refer to here as the Matese fault. The major lithological discontinuity between crystalline and sedimentary rocks of Apulia likely confined upward the rupture extent of the Matese fault. Repeated coseismic failure represented by the deeper group of events in the sequence, activated in a passive fashion the overlying ∼11–15 km deep section of the upper crustal normal faults. We consider the southwest-dipping Matese fault representative of a poorly known type of seismogenic structures in the Southern Apennines, where extensional seismogenesis and geodetic strain accumulation occur more frequently on NE-dipping, shallower-rooted faults. This is the case of the Boiano Basin fault located on the northern side of the massif, to which the 1997–1998 sequence is related. The close proximity of the two types of seismogenic faults at the Matese Massif is related to the complex crustal architecture generated by the Pliocene–early Pleistocene contractional and transpressional tectonics.
    Description: Published
    Description: 823-837
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: partially_open
    Keywords: Seismicity and tectonics ; Continental tectonics: extensional ; Crustal structure ; 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::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
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  • 95
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    Empirical conversion between teleseismic magnitudes (mb and Ms) and moment magnitude (Mw) at the Global, Euro-Mediterranean and Italian scale (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We analysed the conversion problem between teleseismic magnitudes (Ms and mb) provided by the Seismological Bulletin of the International Seismological Centre and moment magni- tudes (Mw) provided by online moment tensor (MT) catalogues using the chi-square general orthogonal regression method (CSQ) that, differently from the ordinary least-square regres- sion method (OLS), accounts for the measurement errors of both the predictor and response variables. To account for the non-linearity of the relationships, we used two types of curvilin- ear models: (i) the exponential model (EXP), recently proposed by the authors of the Global Catalogue sponsored by the Global Earthquake Model (GEM) Foundation and (ii) a connected bilinear (CBL) model, similar to that proposed by Ekstro ̈m & Dziewonski, where two different linear trends at low and high magnitudes are connected by an arc of circle that preserves the continuity of the function and of its first derivative at the connecting points. For Ms, we found that the regression curves computed for a global data set (GBL) are likely to be biased by the incompleteness of global MT catalogues for Mw 〈5.0–5.5. In fact, the GBL curves deviate significantly from a similar regression curve computed for a Euro-Mediterranean data set (MED) integrated with the data provided by two regional MT catalogues including many more events with Mw 〈 5.0–5.5. The GLB regression curves overestimate the Mw proxies computed from Ms up to 0.5 magnitude units. Hence for computing Mw proxies at the global scale of Ms ≤ 5.5, we suggest to adopt the coefficients obtained from the MED regression. The analysis of the frequency–magnitude relationship of the resulting Mw proxy catalogues confirms the validity of this choice as the behaviour of b-value as a function of cut-off magnitude of the GBL data set is much more stable using such approach. The incompleteness of Mw’s provided from MT global catalogues also affects the mb GBL data set but in this case the use of the CSQ regression method, in place of the OLS, mitigates the bias and then, at low magnitudes, the EXP regression curve computed from the more complete MED data set almost coincides with that computed from the GBL data set. Our results also indicate that the slope at low magnitudes of the Mw–Ms relationship is substantially consistent with the hypothesized theoretical value of 2/3 for Ms 〈 5.0 while the slope of the Mw–mb relationship at high magnitudes probably reaches the theoretically expected value of 2 only in the proximity of the upper limit of mb determinations in our data set (mb = 7.2).
    Description: Published
    Description: 805–828
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake source observations ; Statistical seismology ; 05. General::05.02. Data dissemination::05.02.02. Seismological data
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  • 96
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    Reddish Metagranites from the Gennargentu Igneous Complex (Sardinia, Italy): insight into metasomatism induced by magma mingling (2015)
    Oxford University Press
    Details
    Publication Date: 2017-04-04
    Description: The mineralogy of thermometamorphic granites is relatively simple, making it possible to track the spatial distribution of chemical and mineralogical variations in these rocks and investigate the processes that underpin these metamorphic reactions.We have undertaken a detailed investigation of metagranites from the contact aureole that fringes a quartz diorite intrusion of Late Permian age, emplaced into Carboniferous peraluminous granites of the Gennargentu Igneous Complex (Sardinia, Italy). New data are presented including the petrography of metagranites within a 500 m zone adjacent to the quartz diorite intrusion, the compositions of minerals and bulk-rocks, and the oxygen isotope compositions of separated minerals. We have used these data to assess the mobility of elements, expressed as oxide, in the aureole, and the physical conditions of fluid-assisted thermometamorphism. Modal variations and the oscillatory zoning of plagioclase demonstrate that the shallow (P 200MPa) quartz diorite intrusion was emplaced through a number of magmatic injections.The border zone of the quartz diorite intrusion presents evidence of two main processes: hybridization between andesite and rhyolite magmas and volatile saturation of the mingled magma. Modal differences in the contact zone with respect to the protolith (i.e. peraluminous granite), variations in mineral composition, temperature constraints and K2O, Na2O, SiO2 and Al2O3 indicate that a relatively large volume of the host granite (up to 400 m from the contact) was metasomatized by high-temperature (650^3508C) fluids derived from the mingled zone of the quartz diorite intrusion. In detail, the metasomatic K2O-rich fluid reacted with albite to form K-feldspar, and triggered the recrystallization of quartz and plagioclase to higher calcium concentrations. The progressive increase in the MgO/(MgOþFeO) of chlorite closer to the contact indicates that this phase also recrystallized. The iron released during chlorite recrystallization was buffered by hematite formation in the pores of metasomatic K-feldspar. The Gennargentu metagranites provide evidence that metasomatic fluids can play a major role in driving metamorphic reactions in contact aureoles. For instance, the expected increase of Ca in plagioclase owing to thermal equilibration was not achieved in the high-T zone of the aureole because of fluid-assisted removal of cations.We conclude that caution should be taken when interpreting the processes that underpin contact metamorphism in terms of thermally driven, ionic diffusion alone, because the role of fluids may be significant, if not overwhelming, in the domains closest to the magmatic source.
    Description: Published
    Description: 839-859
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: contact metamorphism ; metasomatism ; red metagranites ; oxygen isotopes ; Gennargentu Igneous Complex ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology
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  • 97
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    Comment on ‘Are the source models of the M 7.1 1908 Messina Straits earthquake reliable? Insights from a novel inversion and sensitivity analysis of levelling data’ by M. Aloisi, V. Bruno, F. Cannav ` o, L. Ferranti, M. Mattia, C. Monaco and M. Palano (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: In a recent paper, important issues were raised about the identification of the fault responsible for the 1908 Messina Straits earthquake. Starting with a reanalysis of the available original geodetic data, the authors aimed to demonstrate that both of the fault–plane orientations derived by the focal mechanism are compatible with the measurements. On these grounds, and based on geological considerations, they argued in favour of the Armo fault—a high-angled structure on the Calabrian side of the Messina Straits—as responsible for the 1908 earthquake. We indicate here that their analysis has some pitfalls that produce questionable results, and that render their conclusions unreliable. Moreover, especially when dealing with such old events and data, we consider that it is more prudent not to derive conclusions on the basis of a single data set, as all of the available information should be included in any interpretation. Indeed, when the joint results of the seismological and geodetic analyses are taken into account, a consistent and robust source model can be derived that indicates that a low-angle, east-dipping fault is the most likely source of this 1908 Messina Straits earthquake
    Description: Published
    Description: 1399-1402
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake source observations; Seismicity and tectonics; Europe ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
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  • 98
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    Deformation of the western Indian plate boundary: insights from differential and multi-aperture InSAR data inversion of the 2008, Baluchistan (Western Pakistan) seismic sequence (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: In this study,we use Differential Synthetic Aperture Radar Interferometry (DInSAR) and multiaperture interferometry (MAI) to constrain the sources of the three largest events of the 2008 Baluchistan (western Pakistan) seismic sequence, namely two Mw 6.4 events only 12 hr apart and an Mw 5.7 event that occurred 40 d later. The sequence took place in the Quetta Syntaxis, the most seismically active region of Baluchistan, tectonically located between the colliding Indian Plate and the Afghan Block of the Eurasian Plate. Surface displacements estimated from ascending and descending ENVISAT ASAR acquisitions were used to derive elastic dislocation models for the sources of the two main events. The estimated slip distributions have peak values of 120 and 130 cm on a pair of almost parallel and near-vertical faults striking NW–SE, and of 50 cm and 60 cm on two high-angle faults striking NE–SW. Values up to 50 cm were found for the largest aftershock on an NE–SW fault located between the sources of the main shocks. The MAI measurements, with their high sensitivity to the north–south motion component, are crucial in this area to accurately describe the coseismic displacement field. Our results provide insight into the deformation style of the Quetta Syntaxis, suggesting that right-lateral slip released at shallow depths on large NW fault planes is compatible with left-lateral activation on smaller NE–SW faults.
    Description: Published
    Description: 25-39
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: Radar interferometry ; Satellite geodesy ; Seismicity and Tectonics ; Continental margins: convergent ; Earthquake interaction, forecasting and prediction ; Earthquake source observation ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
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  • 99
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    Monitoring of crustal seismic velocity variations in the L'Aquila fault zone inferred from noise cross-correlation (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: The relative seismic velocity variations possibly associated to large earthquakes can be readily monitored via cross-correlation of seismic noise. In a recently published study, more than 2 yr of continuous seismic records have been analysed from three stations surrounding the epicentre of the 2009 April 6, Mw 6.1 L’Aquila earthquake, observing a clear decrease of seismic velocities likely corresponding to the co-seismic shaking. Here, we extend the analysis in space, including seismic stations within a radius of 60 km from the main shock epicentre, and in time, collecting 5 yr of data for the six stations within 40 km of it. Our aim is to investigate how far the crustal damage is visible through this technique, and to detect a potential post-seismic recovery of velocity variations. We find that the co-seismic drop in velocity variations extends up to 40 km from the epicentre, with spatial distribution (maximum around the fault and in the north– east direction from it) in agreement with the horizontal co-seismic displacement detected by global positioning system (GPS). In the first few months after L’Aquila earthquake, the crust’s perturbation in terms of velocity variations displays a very unstable behaviour, followed by a slow linear recovery towards pre-earthquake conditions; by almost 4 yr after the event, the co-seismic drop of seismic velocity is not yet fully recovered. The strong oscillations of the velocity changes in the first months after the earthquake prevent to detect the fast exponential recovery seen by GPS data. A test of differently parametrized fitting curves demonstrate that the post-seismic recovery is best explained by a sum of a logarithmic and a linear term, suggesting that processes like viscoelastic relaxation, frictional afterlip and poroelastic rebound may be acting concurrently.
    Description: Published
    Description: 604-6011
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: restricted
    Keywords: Time-series analysis; Interferometry; Computational seismology; Europe ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
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  • 100
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    Active extension in Val d’Agri area, Southern Apennines, Italy: implications for the geometry of the seismogenic belt. (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2020-02-24
    Description: Integration of geologic, geomorphologic and seismologic data sets is used to reconstruct the recent tectonic evolution and active deformation pattern in the Val d’Agri area, located in the seismically active axial sector of the Southern Apennines (Italy). The western portion of the Apennines thrust belt has been affected by Pliocene–Quaternary extension during easterly roll-back and crustal delamination of the Adriatic slab. The bulk of Quaternary extension has been accommodated bySW-dipping oblique and normal faults,which have attained mature morphologic and structural features and, nowadays, separate mountain ranges from intermontane basins. However, in the present seismogenic belt, coseismic faulting locally occurs on NE-dipping structures, which might cut the inherited Pleistocene landscape. In theVal d’Agri basin, in spite of the large Early–Middle Pleistocene, displacement occurred on SW-dipping faults bordering its eastern flank, our investigations show that the recent basin evolution has been controlled by a NE-dipping fault system (Monti della Maddalena fault system, MMFS). This fault system cuts across the Monti della Maddalena range, west of the Agri valley and has not yet created an evident tectonic landscape. Notwithstanding, fault motion since the Middle Pleistocene might explain geomorphologic and hydrographic anomalies of the Agri river and its valley, where fault-controlled subsidence has captured the river course and produced an aggrading plain within a regional uplift context. Recent and ongoing motion is documented by fault scarplets in loose deposits, 14C ages of palaeosols and the spatial relation with low to moderate instrumental seismicity. Results from fault kinematic analysis are compatible with fault-plane solutions of local and regional seismic events, and indicate ∼NE–SW oriented extension. Recognition of the MMFS as a potential seismogenic fault increases the longitudinal extent of the NE-dipping, morphologically immature seismic sources in the Southern Apennines and argues against the range-bounding fault model for active extension in the region. The regional size of the NE-dipping seismogenic belt may result from impingement of a mantle wedge beneath the Apenninic chain and possibly track the external front of crustal delamination.
    Description: Published
    Description: 591-609
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: active tectonics ; crustal deformation ; earthquakes ; geomorphology ; normal faulting ; 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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