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  • AGU  (19)
  • Wiley  (3)
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  • 1
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    Italian and Alpine three-dimensional crustal structure imaged by ambient-noise surface-wave dispersion (2015)
    Wiley
    Details
    Publication Date: 2015-12-09
    Description: We derive the 3D crustal structure (S wave velocity) underneath Italy and the Alpine region, expanding and exploiting the database of ambient noise Rayleigh-wave phase- and group-velocity of verbeke et al . [2012]. We first complement the database of verbeke et al . [2012] with a dense set of new ambient-noise-based phase-velocity observations. We next conduct a suite of linear least squares inversion of both phase- and group-velocity data, resulting in 2D maps of Rayleigh-wave phase and group velocity at periods between 5 and 37 s. At relatively short periods, these maps clearly reflect the surface geology of the region, e.g. low velocity zones at the Po Plain; at longer periods, deeper structures such as Moho topography under Alps and Apennines, and lower-crust anomalies are revealed. Our phase- and group-velocity models are next inverted via the Neighbourhood Algorithm to determine a set of one-dimensional shear-velocity models (one per phase/group-velocity pixel), resulting in a new three-dimensional model of shear velocity ( υ S ) parameterized in the same way as the European reference crustal model EPcrust [ Molinari and Morelli, 2011]. We also show how well υ S is constrained by phase and group dispersion curves. The model shows the low velocity area beneath the Po Plain and the Molasse basin; the contrast between the low-velocity crust of the Adriatic domain and the high-velocity crust of the Tyrrhenian domain is clearly seen, as well as an almost uniform crystalline crust beneath the Alpine belt. Our results are discussed from the geological/geodynamical standpoint, and compared to those of other, interdisciplinary studies. This article is protected by copyright. All rights reserved.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    The influence of non-uniform ambient noise on crustal tomography in Europe (2013)
    Wiley
    Details
    Publication Date: 2013-03-02
    Description: [1]  Ambient-noise seismology is of great relevance to high-resolution crustal imaging, thanks to the unprecedented dense data coverage it affords in regions of little seismicity. Under the assumption of uniformly distributed noise sources, it has been used to extract the Green’s function between two receivers. We determine the imprint of this assumption by means of wave propagation and adjoint methods in realistic 3D Earth models. In this context, we quantify the sensitivity of ambient-noise cross correlations from central Europe with respect to noise-source locations and shear wavespeed structure. We use ambient noise recorded over one year at 196 stations, resulting in a database of 864 cross-correlations. Our mesh is built upon a combined crustal and 3D tomographic model. We simulate synthetic ambient-noise cross-correlations in different frequency bands using a 3D spectral-element method. Traveltime cross-correlation measurements in these different frequency bands define the misfit between synthetics and observations as a basis to compute sensitivity kernels using the adjoint method. We perform a comprehensive analysis varying geographic station and noise-source distributions around the European seas. The deterministic sensitivity analysis allows for estimating where the starting crustal model shows better accordance with our dataset and gain insight into the distribution of noise sources in the European region. This highlights the potential importance to consider localized noise distributions for tomographic imaging and forms the basis of a tomographic inversion in which the distribution of noise sources may be treated as a free parameter similar to earthquake tomography.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    A new dyke intrusion style for the Mount Etna May 2008 eruption modelled through continuous tilt and GPS data (2009)
    Wiley
    Details
    Publication Date: 2009-08-01
    Print ISSN: 0954-4879
    Electronic ISSN: 1365-3121
    Topics: Geosciences
    Published by Wiley
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  • 4
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    An EGF technique to infer the rupture velocity history of a small magnitude earthquake (2008)
    AGU
    Details
    Publication Date: 2021-05-11
    Description: An empirical Green’s function (EGF) technique has been developed to detect the rupture velocity history of a small earthquake. The assumed source model is a circular crack that is characterized by a single and unipolar moment rate function (MRF). The deconvolution is treated as an inverse problem in the time domain, which involves an assumed form of the moment rate function (MRF). The source parameters of the MRF are determined by adopting a global nonlinear inversion scheme. A thorough synthetic study on both synthetic and real seismograms allowed us to evaluate the degree of reliability of the retrieved model parameters. The technique was applied to four small events that occurred in the Umbria-Marche region (Italy) in 1997. To test the hypothesis of a single rupture process, the inversion results were compared with those arising from another EGF technique, which assumes a multiple rupture process. For each event, the best fit model was selected using the corrected Akaike Information Criterion. For all the considered events the most interesting result is that the selected best fit model favors the hypothesis of a single faulting process with a clear variability of the rupture velocity during the process. For the studied events, the maximum rupture speed can even approach the P-wave velocity at the source, as theoretically foreseen in studies of the physics of the rupture and recently observed for high-magnitude earthquakes.
    Description: Published
    Description: B10314
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: EGF technique ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
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    Potential Field modeling of collapse-prone submarine volcanoes in the southern Tyrrhenian Sea (Italy) (2010)
    AGU
    Details
    Publication Date: 2021-07-14
    Description: Hydrothermal alteration may weaken volcanic rocks, causing the gravitational instability of portions of active volcanoes with potentially hazardous collapses. Here we show high‐resolution multibeam, magnetic and gravity surveys of the Marsili seamount, the largest active volcano of Europe located in the southern Tyrrhenian back‐arc basin. These surveys reveal zones with exceptionally low densities and with vanishing magnetizations, due probably to the comminution of basalts during hyaloclastic submarine eruptions and to their post‐eruptive hydrothermal alteration. The location of these regions correlates with morphological data showing the occurrence of past collapses. Similar evidence has been obtained from pre existing data at Vavilov Seamount, another older volcanic system in the Tyrrhenian back‐arc basin. Here a large volume of at least 50 km3 may have collapsed in a single event from its 40 km long western flank. Given the similarities between these volcanoes, a large collapse event may also be expected at Marsili.
    Description: Published
    Description: L03305
    Description: 2.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attive
    Description: 3.4. Geomagnetismo
    Description: JCR Journal
    Description: reserved
    Keywords: Marsili Seamount ; Gravity anomalies ; Magnetic anomalies ; Tyrrhenian Sea ; 04. Solid Earth::04.02. Exploration geophysics::04.02.02. Gravity methods ; 04. Solid Earth::04.04. Geology::04.04.04. Marine geology ; 04. Solid Earth::04.05. Geomagnetism::04.05.04. Magnetic anomalies ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
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    History of glacial terminations from the Tiber River, Rome: Insights into glacial forcing mechanisms (2008)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We document the aggradational history of the Tiber River delta through the last 17,000 years by means of 17 new 14C ages from peat or wood collected from the delta sediment. An abrupt change in sediment clast size, grading from gravel to clay, occurred between 13.63 (±0.20) and 12.80 (±0.15) ka, indicating that it was synchronous with the last glacial termination, with no appreciable phase lag. Knowing this phase relationship enables us to reduce the magnitudes of age uncertainties for aggradational sections corresponding to glacial terminations IX through III, which we had dated previously by 40Ar/39Ar methods. Glacial terminations VIII, VI, and IV precede beyond 95% confidence the ages predicted by Northern Hemisphere summer insolation maxima. Additionally, we find that each of these seven glacial terminations follows particularly mild insolation minima, which we suggest may be regarded as the preconditioning factor to trigger a glacial termination.
    Description: Published
    Description: PA2205
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: reserved
    Keywords: climate changes ; 01. Atmosphere::01.01. Atmosphere::01.01.03. Pollution ; 03. Hydrosphere::03.01. General::03.01.06. Paleoceanography and paleoclimatology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    Reply to comments by E.Galili et al. on “Holocene Tsunami's from Mount Etna and the fate of Israeli Neolithic Communities” (2008)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: No abstract
    Description: Published
    Description: L08312
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: reserved
    Keywords: landslide tsunami ; Mt. Etna ; paleo-tsunami deposits ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Coseismic deformation of the destructive April 6, 2009 L’Aquila earthquake (central Italy) from GPS data (2010)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: On April 6, 2009, 01:32:39 GMT, the city of L’Aquila was struck by a Mw 6.3 earthquake that killed 307 people, causing severe destruction and ground cracks in a wide area around the epicenter. Four days before the main shock we augmented the existing permanent GPS network with five GPS stations of the Central Apennine Geodetic Network (CaGeoNet) bordering the L’Aquila basin. The maximum horizontal and vertical coseismic surface displacements detected at these stations was 10.39 ± 0.45 cm and 15.64 ± 1.55 cm, respectively. Fixing the strike direction according to focal mechanism estimates, we estimated the source geometry with a non linear inversion of the geodetic data.Our best fitting fault model is a 13 15.7 km2 rectangular fault,SW-dipping at 55.3 ± 1.8 , consistent with the position of observed surface ruptures. The estimated slip (495 ± 29 mm) corresponds to a 6.3 moment magnitude, in excellent agreement with seismological data.
    Description: Published
    Description: L17307
    Description: 1.9. Rete GPS nazionale
    Description: JCR Journal
    Description: reserved
    Keywords: L'Aquila Earthquake ; GPS ; 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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  • 9
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    The large earthquake on 29 June 1170 (Syria, Lebanon, and central southern Turkey) (2007)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: On 29 June 1170 a large earthquake hit a vast area in the Near Eastern Mediterranean, comprising the present-day territories of western Syria, central southern Turkey, and Lebanon. Although this was one of the strongest seismic events ever to hit Syria, so far no in-depth or specific studies have been available. Furthermore, the seismological literature (from 1979 until 2000) only elaborated a partial summary of it, mainly based solely on Arabic sources. The major effects area was very partial, making the derived seismic parameters unreliable. This earthquake is in actual fact one of the most highly documented events of the medieval Mediterranean. This is due to both the particular historical period in which it had occurred (between the second and the third Crusades) and the presence of the Latin states in the territory of Syria. Some 50 historical sources, written in eight different languages, have been analyzed: Latin (major contributions), Arabic, Syriac, Armenian, Greek, Hebrew, Vulgar French, and Italian. A critical analysis of this extraordinary body of historical information has allowed us to obtain data on the effects of the earthquake at 29 locations, 16 of which were unknown in the previous scientific literature. As regards the seismic dynamics, this study has set itself the question of whether there was just one or more than one strong earthquake. In the former case, the parameters (Me 7.7 ± 0.22, epicenter, and fault length 126.2 km) were calculated. Some hypotheses are outlined concerning the seismogenic zones involved.
    Description: Published
    Description: B07304
    Description: 3.10. Sismologia storica e archeosismologia
    Description: JCR Journal
    Description: reserved
    Keywords: Historical earthquakes ; Syria ; Lebanon ; central southern Turkey ; seismogenic source ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.05. Historical seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
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    Reappraisal of the fossil methane budget and related emission from geologic sources (2008)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: Converging evidence from new top-down and bottomup estimates of fossil "radiocarbon-free" methane emissions indicates that natural geologic sources account for a substantial component of the atmospheric methane budget. Comparing emission estimates based on atmospheric 14CH4 ("radiomethane") with geologic emissions from seepage, including terrestrial macroseeps, microseepage, marine seeps, and geothermal/volcanic emissions from the Earth’s crust, shows that such "geo-CH4" sources can be conservatively estimated at 53 ± 11 Tg yr 1 globally. This makes geo-CH4 second in importance to wetlands as a natural methane source. Such a new appraisal can easily be accommodated within the uncertainty of the global methane budget as recently compiled, and recognizes the importance of geophysical out-gassing of methane generated within the lithosphere. We propose a new coherent contemporary budget in which 30 ± 5% (based on atmospheric radiomethane measurements) of the global source of 582 ± 87 Tg yr 1 has fossil origin, both natural and anthropogenic.
    Description: Published
    Description: L09307
    Description: 3.8. Geofisica per l'ambiente
    Description: JCR Journal
    Description: reserved
    Keywords: methane ; greenhouse-gas ; lithosphere degassing ; 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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