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  • 04. Solid Earth::04.04. Geology::04.04.09. Structural geology  (21)
  • 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics  (15)
  • 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics  (15)
  • 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution  (14)
  • 04.06. Seismology
  • Creep observations and analysis
  • Elsevier Science Limited  (51)
  • EGU - Copernicus
  • Wiley
Collection
Keywords
  • 1
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    Wiley
    In:  Bull., Polar Proj. OP-O3A4, Earth Rheology, Isostasy and Eustasy, London, Wiley, vol. 13, no. 4, pp. 125-134, (ISBN 0080419208)
    Publication Date: 1979
    Keywords: Rheology ; Creep observations and analysis ; Lithosphere
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  • 2
    Publication Date: 2021-01-22
    Description: Spectral analysis has been applied to almost thou-sand seismic events recorded at Vesuvius volcano (Naples,southern Italy) in 2018 with the aim to test a new tool fora fast event classification. We computed two spectral pa-rameters, central frequency and shape factor, from the spec-tral moments of order 0, 1, and 2, for each event at sevenseismic stations taking the mean among the three compo-nents of ground motion. The analyzed events consist ofvolcano-tectonic earthquakes, low frequency events and un-classified events (landslides, rockfall, thunders, quarry blasts,etc.). Most of them are of low magnitude, and/or low maxi-mum signal amplitude, therefore the signal to noise ratio isvery different between the low noise summit stations andthe higher noise stations installed at low elevation aroundthe volcano. The results of our analysis show that volcano-tectonic earthquakes and low frequency events are easily dis-tinguishable through the spectral moments values, particu-larly at seismic stations closer to the epicenter. On the con-trary, unclassified events show the spectral parameters valuesdistributed in a broad range which overlap both the volcano-tectonic earthquakes and the low frequency events. Since thecomputation of spectral parameters is extremely easy and fastfor a detected event, it may become an effective tool for eventclassification in observatory practice.
    Description: Published
    Description: 67–74
    Description: 1SR TERREMOTI - Sorveglianza Sismica e Allerta Tsunami
    Description: N/A or not JCR
    Keywords: Vesuvius ; Spectral Analisys ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2021-05-12
    Description: This study presents a series of self-correcting models that are obtained by integrating information about seismicity and fault sources in Italy. Four versions of the stress release model are analyzed, in which the evolution of the system over time is represented by the level of strain, moment, seismic energy, or energy scaled by the moment. We carry out the analysis on a regional basis by subdividing the study area into eight tectonically coherent regions. In each region, we reconstruct the seismic history and statistically evaluate the completeness of the resulting seismic catalog. Following the Bayesian paradigm, we apply Markov chain Monte Carlo methods to obtain parameter estimates and a measure of their uncertainty expressed by the simulated posterior distribution. The comparison of the four models through the Bayes factor and an information criterion provides evidence (to different degrees depending on the region) in favor of the stress release model based on the energy and the scaled energy. Therefore, among the quantities considered, this turns out to be the measure of the size of an earthquake to use in stress release models. At any instant, the time to the next event turns out to follow a Gompertz distribution, with a shape parameter that depends on time through the value of the conditional intensity at that instant. In light of this result, the issue of forecasting is tackled through both retrospective and prospective approaches. Retrospectively, the forecasting procedure is carried out on the occurrence times of the events recorded in each region, to determine whether the stress release model reproduces the observations used in the estimation procedure. Prospectively, the estimates of the time to the next event are compared with the dates of the earthquakes that occurred after the end of the learning catalog, in the 2003–2012 decade.
    Description: Italian Dipartimento della Protezione Civile in the framework of the 2007–2009 Agreement with Istituto Nazionale di Geofisica e Vulcanologia (INGV), project S1: Analysis of the seismic potential in Italy for the evaluation of the seismic hazard.
    Description: Published
    Description: 147-168
    Description: 2T. Tettonica attiva
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: point process ; probabilistic forecasting ; interevent time distribution ; seismogenic sources ; Bayesian inference ; 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::04.06.02. Earthquake interactions and probability ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
    Publication Date: 2021-06-08
    Description: Source parameters of the mainshock (ML=5.3) and of 165 aftershocks (0.8 〈 ML 〈 3.5) of the 2004 Kobarid (Western Slovenia) seismic sequence are investigated in order to determine the corresponding source scaling relations. Data recorded from July to December 2004 by the Friuli and Veneto seismic network (FV), managed by the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS) and installed in Northeastern Italy, are employed to obtain the SH-wave amplitude Fourier spectra of the selected earthquakes. For source spectra computation, we consider only records with significant values of the signal-to-noise ratio and, to account for local amplifications, we compute standard H/V spectral ratios (HVSR) for all the stations of the network. After correction for attenuation effects, source spectra obtained at stations with negligible site effects show a good fit with a ω-square model. We adopt different approaches to compute the source parameters and final results are chosen based on the obtained misfits between observed and theoretical source spectra. For 21 earthquakes of the sequence the obtained results are confirmed by the Empirical Green Function (EGF) technique, applied by estimating the spectral ratios of couples of events with hypocentral distance differences smaller than 500 m and magnitude differences greater than 1. The mainshock of the sequence is characterized by a seismic moment of 3.5x10^16 Nm and a corner frequency of 0.8 Hz, corresponding, in the Brune’s model (1970), to a fault radius of 1465 m and a stress drop of 4.9 MPa. Aftershocks have seismic moments in the range [3.3x10^11, 1.8x10^14] Nm, corner frequencies between 1.9 and 12.4 Hz (Brune radii between 95 and 638 m) and stress drops in the range [0.03, 1.55] MPa. The observed scaling of seismic moment (M0) with the local magnitude (ML) is consistent with the trend: Log M0 = 1.06 ML + 10.56. The Brune radius (rB) increases with the seismic moment according to: Log rB = 0.22 Log M0 - 0.40. Moreover, in spite of the high dispersion that characterizes the estimates of the Brune stress drop (ΔσB), we observe also an increase of ΔσB with M0. The mainshock is characterized by 2.4 x10^12 J radiated energy (ES) and 1.9 MPa apparent stress (σa). Aftershocks have energies between 2.0 x10^5 and 7.4 x10^8 J and apparent stress values increasing with the seismic moment in the range [0.01, 0.48] MPa. Radiated energies increase with seismic moments according to the empirical relationship: Log ES = 1.53 Log M0 - 12.47. The scaling of both ΔσB and σa with M0 in the range of magnitude between 0.8 to 5.3, evidences the non-self-similarity characteristics of the 2004 Kobarid seismic sequence. Similar results have been obtained by previous studies concerning the source parameter scaling of the background seismicity and of other seismic sequences of the area.
    Description: Published
    Description: 58-75
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquakes ; Source parameters ; Scaling law ; Seismic sequences ; Northeastern Italy ; Western Slovenia ; 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
    Publication Date: 2021-06-25
    Description: The 11 March 2011 Tohoku earthquake was the strongest event recorded in recent historic seismicity in Japan. Several researchers reported the deformation and possible mechanism as triggered by a mega thrust fault located offshore at the interface between the Pacific and the Okhotsk Plate. The studies to estimate the deformation in detail and the dynamics involved are still in progress. In this paper, coseismic GPS displacements associated with Tohoku earthquake are used to infer the amount of slip on the fault plane. Starting from the fault displacements configuration proposed by Caltech-JPL ARIA group and Geoazur CNRS, an optimization of these displacements is performed by developing a 3D finite element method (FEM) model, including the data of GPS-acoustic stations located offshore. The optimization is performed for different scenarios which include the presence of topography and bathymetry (DEM) as well as medium heterogeneities. By mean of the optimized displacement distribution for the most complete case (heterogeneous with DEM), a broad slip distribution, not narrowly centered east of hypocenter, is inferred. The resulting displacement map suggests that the beginning of the area of subsidence is not at east of MYGW GPS-acoustic station, as some researchers have suggested, and that the area of polar reversal of the vertical displacement is rather located at west of MYGW. The new fault slip distribution fits well for all the stations at ground and offshore and provides new information on the earthquake generation process and on the kinematics of Northern Japan area.
    Description: Published
    Description: 25-39
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: 2011 Tohoku earthquake ; Fault slip distribution ; Numerical FEM optimization ; Upper plate rebound ; 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::04.03. Geodesy::04.03.08. Theory and Models ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
    Publication Date: 2020-12-15
    Description: The Africa–Eurasia convergence in Sicily and southern Calabria is currently expressed by two different tectonic and geodynamic domains: thewestern region, governed by a roughlyN–S compression generated by a continental collision; the eastern one, controlled by a NW–SE extension related to the south-east-directed expansion of the Calabro–Peloritan Arc. The different deformation pattern of these two domains is accommodated by a right-lateral shear zone (Aeolian–Tindari–Letojanni fault system) which, from the Ionian Sea, north of Mt. Etna, extends across the Peloritani chain to the Aeolian Islands. In this work, we study the evidence of active tectonics characterizing this shear zone, through the analysis of seismic and geodetic data acquired by the INGV networks in the last 15 years. The study is completed by structural and morphological surveys carried out between Capo Tindari and the watershed of the chain. The results allowed defining a clear structural picture depicting the tectonic interferences between the two different geodynamic domains. The results indicate that, besides the regional ~N130°E horizontal extensional stress field, another one, NE–SW-oriented, is active in the investigated area. Both tension axes are mutually independent and have been active up to the present at different times. The coexistence of these different active horizontal extensions is the result of complex interactions between several induced stresses: 1) the regional extension (NW–SE) related to the slab rollback and back-arc extension; 2) the strong uplift of the chain; 3) the accommodation between compressional and extensional tectonic regimes along the Aeolian– Tindari–Letojanni faults, through a SSE–NNW right-lateral transtensional displacement. In these conditions, the greater and recurring uplift activity is not able to induce a radial extensional dynamics, but, under the “directing” action of the shear system, it can only act on the regional extension (NW–SE) and produce the second system of extension (NE–SW).
    Description: Published
    Description: 1-17
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: open
    Keywords: Africa–Eurasia convergence ; Aeolian–Tindari fault system ; Transform activity ; Stress and strain fields ; Multidisciplinary approach ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 7
    Publication Date: 2021-01-27
    Description: We model a fault cross-cutting the brittle upper crust and the ductile lower crust. In the brittle layer the fault is assumed to have stick–slip behaviour, whereas the lower ductile crust is inferred to deform in a steady-state shear. Therefore, the brittle–ductile transition (BDT) separates two layers with different strain rates and structural styles. This contrasting behaviour determines a stress gradient at the BDT that is eventually dissipated during the earthquake. During the interseismic period, along a normal fault it should form a dilated hinge at and above the BDT. Conversely, an over-compressed volume should rather develop above a thrust plane at the BDT. On a normal fault the earthquake is associated with the coseismic closure of the dilated fractures generated in the stretched hangingwall during the interseismic period. In addition to the shear stress overcoming the friction of the fault, the brittle fault moves when the weight of the hangingwall exceeds the strength of the dilated band above the BDT. On a thrust fault, the seismic event is instead associated with the sudden dilation of the previously over-compressed volume in the hangingwall above the BDT, a mechanism requiring much more energy because it acts against gravity. In both cases, the deeper the BDT, the larger the involved volume, and the bigger the related magnitude. We tested two scenarios with two examples from L’Aquila 2009 (Italy) and Chi-Chi 1999 (Taiwan) events. GPS data, energy dissipation and strain rate analysis support these contrasting evolutions. Our model also predicts, consistently with data, that the interseismic strain rate is lower along the fault segment more prone to seismic activation.
    Description: Published
    Description: 160-161
    Description: JCR Journal
    Description: open
    Keywords: faul activation ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
    Publication Date: 2021-03-19
    Description: From simple considerations we propose a revision of the AcceleratingMoment Release (AMR) methodology for improving our knowledge of seismic sequences and then, hopefully in a close future, to reach the capability of predicting the main-shock location and occurrence with sufficient accuracy. The proposed revision is based on the introduction of a “reduced” Benioff strain for the earthquakes of the seismic sequence where, for the same magnitude and after a certain distance from the main-shock epicentre, the closer the events the more they are weighted. In addition,we retain the usual expressions proposed by the ordinary AMRmethod for the estimation of the corresponding main-shock magnitude, although this parameter is the weakest of the analysis. Then, we apply the revised method to four case studies in Italy, three of which are the most recent seismic sequences of the last 9 years culminating with a shallow main-shock, and one is instead a 1995–1996 swarm with no significant main-shock. The application of the R-AMRmethodology provides the best results in detecting the precursory seismic acceleration,when comparedwith those found by ordinaryAMR technique.We verify also the stability of the results in space, applying the analysis to real data with moving circles in a large area around each mainshock epicentre, and the efficiency of the revised technique in time, comparing the results with those obtained when applying the same analysis to simulated seismic sequences.
    Description: Published
    Description: 82–98
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake interaction ; Forecasting and prediction ; Seismicity and tectonics ; Seismic attenuation ; Seismic sequence ; Foreshocks ; 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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  • 9
    Publication Date: 2021-03-02
    Description: This study presents new geological and seismological data that are used to assess the seismic hazard of a sector of the Po Plain (northern Italy), a large alluvial basin hit by two strong earthquakes on May 20 (Mw 6.1) and May 29 (Mw 6.0), 2012. The proposed interpretation is based on high-quality relocation of 5,369 earthquakes ( 'Emilia sequence‘) and a dense grid of seismic profiles and exploration wells. The analysed seismicity was recorded by 44 seismic stations, and initially used to calibrate new one-dimensional and three- dimensional local Vp and Vs velocity models for the area. Considering these new models, the initial sparse hypocenters were then relocated in absolute mode and adjusted using the double-difference relative location algorithm. These data define a seismicity that is elongated in the W-NW to E-SE directions. The aftershocks of the May 20 mainshock appear to be distributed on a rupture surface that dips ~45° SSW, and the surface projection indicates an area ~10 km wide and 23 km long. The aftershocks of the May 29 mainshock followed a steep rupture surface that is well constrained within the investigated volume, whereby the surface projection of the blind source indicates an area ~6 km wide and 33 km long. Multichannel seismic profiles highlight the presence of relevant lateral variations in the structural style of the Ferrara folds that developed during the Pliocene and Pleistocene. There is also evidence of a Mesozoic extensional fault system in the Ferrara arc, with faults that in places have been seismically reactivated. These geological and seismological observations suggest that the 2012 Emilia earthquakes were related to ruptures along blind fault surfaces that are not part of the Pliocene-Pleistocene structural system, but are instead related to a deeper system that is itself closely related to re-activation of a Mesozoic extensional fault system.
    Description: Published
    Description: 107–123
    Description: 5T. Sorveglianza sismica e operatività post-terremoto
    Description: JCR Journal
    Description: restricted
    Keywords: velocity model ; relocated hypocenters ; double-difference locations ; Po Plain ; May 2012 Emilia earthquakes ; reactivated extensional faults ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 10
    Publication Date: 2021-03-10
    Description: Between the October 2011 and the July 2012, several seismic swarms occurred in the Hyblean foreland domain of SE Sicily (Italy) along the Cavagrande Canyon, one of the most impressive fluvial incisions of Sicily. Despite the low magnitude of the events (main shock with M~3.7), they represent the biggest strain release of the Hyblean area over the last ten years. A careful wave-form analysis of the earthquakes revealed that most of them form a family of ―multiplets‖. These findings allow us to reconstruct the attitude of the accountable fault plane by interpolating their highprecision 3D location parameters into a GIS platform. A detailed morpho-structural analysis, performed at the ideal updip projection of the modelled plane, showed that during the Middle-Late Pleistocene the epicentral area has been deformed by a belt of extensional faults, a segment of which matches well with the computer-generated surface. Despite the field evidence, computed focal solutions support contrasting strike-slip kinematics on the same fault plane, clearly indicating a dextral shearing on this pre-existing normal fault. The seismic swarms nucleated on a small rupture area along a ~10 km long, NW-SE trending fault segment, that could be able to generate M~6 earthquakes. Following our analysis and looking at seismicity distribution in the SE portion of Hyblean area, we asses that a stress pattern reorganization occurred all over the Hyblean foreland between the Late Pleistocene and present-day. Change in the trajectory of the max stress axes (from vertical to horizontal) seems to have involved a pre-existing large scale fault configuration with considerable seismotectonic implications.
    Description: Published
    Description: 215-228
    Description: 1T. Geodinamica e interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Hyblean foreland ; seismic sequences ; fault reactivation ; 3D fault modelling ; stress changing ; seismotectonics ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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