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  • AGU  (19)
  • Agu  (9)
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  • 1
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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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  • 2
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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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  • 3
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    Impact of the Minoan tsunami of Santorini. Simulated scenarios in the Eastern Mediterranean (2007)
    Agu
    Details
    Publication Date: 2017-04-04
    Description: We have simulated the impact of the tsunami generated by the Late Bronze Age (LBA) volcanic eruption of Santorini on the Eastern Mediterranean. Two different tsunami triggering mechanisms were considered: a caldera collapse and pyroclastic flows/surges entering the sea. Simulations include the ‘‘worst’’ input conditions in order to evaluate the maximum possible impacts, but also ‘‘lighter’’ input conditions, compatible with the lack of any tsunami trace on the Northern coasts of Crete. In all the simulations, tsunami propagation is mainly confined to the Southern Aegean. Outside the Aegean, the tsunami impact was negligible and not responsible for the slide-slumping of fine-grained pelagic and/or hemipelagic sediments considered the sources of the sporadically located seadeposits in the Ionian Sea and of the widespread megaturbidite deposits localized in the Ionian and Sirte Abyssal Plains.
    Description: Published
    Description: L18607
    Description: JCR Journal
    Description: reserved
    Keywords: Minoan tsunami ; Santorini ; eastern Mediterranean ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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    Reply to comment by Giuliano F. Panza on “Rarely observed short-period (5–10 s) suboceanic Rayleigh waves propagating across the Tyrrhenian Sea” (2007)
    Agu
    In:  Panza, G. F. (2006), Comment on ‘‘Rarely observed short-period (5– 10 s) suboceanic Rayleigh waves propagating across the Tyrrhenian Sea’’ by A. Rovelli et al., Geophys. Res. Lett., 33, L10309, doi:10.1029/2005GL025584.
    Details
    Publication Date: 2017-04-04
    Description: We thank Giuliano F. Panza for the interest demonstrated in our study and for having pointed out the error in Figure 3 of Rovelli et al. [2004, hereinafter referred to as R2004GRL]. In his comment, Panza writes that a similar phenomenon was already reported by him in an old paper. This statement is not correct and we feel that probably we did not emphasized enough the innovative character of R2004GRL. His comment gives us the opportunity of better explaining that the phenomenon we observe in the Tyrrhenian Sea is different from those studied by Panza and coauthors.
    Description: Published
    Description: L10310
    Description: JCR Journal
    Description: reserved
    Keywords: Reply ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
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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)
    Type: article
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  • 6
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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)
    Type: article
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  • 7
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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)
    Type: article
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  • 8
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    Eruption early warning at Vesuvius: The A.D. 1631 lesson (2007)
    Agu
    Details
    Publication Date: 2017-04-04
    Description: Knowledge of past precursor patterns is crucial for the correct interpretation of monitoring data and reliable volcano forecasting. In the case of Vesuvius, one of the world’s riskiest volcanoes, very little information is available about unrest signals following long periods of quiescence. The translation and analysis of three Latin treatises written from eye-witnesses immediately after the A.D. 1631 subplinian eruption allowed us to reconstruct the sequence of precursors. The progression in the signals was remarkably clear starting at least two to three weeks before the event. Widespread gas emission from the ground coupled with deformation was followed by an increase in seismic activity in the eight days before the eruption. Seismicity escalated both in frequency and intensity in the night before the eruption, heralding the opening of fissures on the volcanic cone. The details of phenomena occurring in the medium-term (months before the eruption) are difficult to evaluate, though it is worth noticing that no major tectonic earthquakes were felt in the area of the volcano. Civil protection preparedness plans should be organized in order to complete the evacuation of people in a time span significantly shorter than the duration of expected short-term precursors.
    Description: Published
    Description: L18317
    Description: JCR Journal
    Description: reserved
    Keywords: Vesuvius ; A. D. 1631 ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 9
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    Computer simulations of lava flow paths in the town of Goma, Nyiragongo volcano, Democratic Republic of Congo (2007)
    Agu
    Details
    Publication Date: 2017-04-04
    Description: The 17 January 2002 fissure eruption of Mount Nyiragongo, Democratic Republic of Congo, produced lava flows which entered and devastated the densely inhabited town of Goma. The 2002 and previous 1977 eruptions demonstrate the high level of volcanic risk in the area. We present an analysis of the susceptibility to lava flow invasion in Goma, by means of computer simulations based on the steepest descent path and probabilisticcomputed flow spreading and obstacle overcoming. The DEM is obtained from a topographic map of Goma by using the DEST algorithm. The numerical results show the distribution of probable lava flow paths from possible vents in the investigated topographic domain. Numerical simulations are validated through comparison with the mapped paths of the 2002 lava flows in Goma. The subsequent investigation includes the analysis of (1) hypothetical lava flow paths from ephemeral vents on the edge of the 2002 lava flows, (2) paths from venting along the hypothetical extension of the 2002 fissures, (3) paths in case of lava flow arrival in town from the north, and (4) changes induced by the presence of the solidified 2002 lava field. The results show the susceptibility of the different parts of the town of Goma to be invaded by future lava flows, and reveal the existence of a large area in town with minimum susceptibility and which can be invaded only in case of venting within it. The areas destroyed by the 2002 lava flows are predicted to be characterized by maximum susceptibility to lava flow invasion.
    Description: Published
    Description: B06202
    Description: JCR Journal
    Description: reserved
    Keywords: Computer simulations ; Nyiragongo volcano ; 05. General::05.01. Computational geophysics::05.01.01. Data processing
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 10
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    Lost tsunami (2007)
    Agu
    Details
    Publication Date: 2017-04-04
    Description: Numerical simulations support the occurrence of a catastrophic tsunami impacting all of the eastern Mediterranean in early Holocene. The tsunami was triggered by a debris avalanche from Mt. Etna (Sicily, Italy) which entered the Ionian Sea in the order of minutes. Simulations show that the resulting tsunami waves were able to destabilize soft marine sediments across the Ionian Sea floor. This generated the well-known, sporadically located, ‘‘homogenite’’ deposits of the Ionian Sea, and the widespread megaturbidite deposits of the Ionian and Sirte Abyssal Plains. It is possible that, 8 ka B.P., the Neolithic village of Atlit-Yam (Israel) was abandoned because of impact by the same Etna tsunami. Two other Pleistocenic megaturbidite deposits of the Ionian Sea can be explained by previous sector collapses from the Etna area.
    Description: Published
    Description: L22608
    Description: JCR Journal
    Description: reserved
    Keywords: tsunami ; collapses ; 05. General::05.09. Miscellaneous::05.09.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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