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  • Articles  (29)
  • 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics  (16)
  • 04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques  (14)
  • INGV  (15)
  • Seismological Society of America  (11)
  • Copernicus Publications  (2)
  • Nature Publishing Group
  • 2010-2014  (29)
Collection
  • Articles  (29)
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Years
Year
  • 1
    Publication Date: 2020-12-22
    Description: On 6 April 2009, a magnitude Mw = 6.1 earthquake struck the Abruzzi region in central Italy. Despite its moderate size, the earthquake caused more than 300 fatalities and partially destroyed the city of L’Aquila and many surrounding villages. In this study we present a retrospective analysis of the rapid source parameters determination procedure developed at INGV (Scognamiglio et al. 2009) as applied to the L’Aquila seismic sequence. Our approach consists of two stages: the near real-time determination of the seismic moment tensor, which is already routinely performed for all M≥ 3.5 earthquakes; and the rapid imaging of the rupture history on a finite fault for earthquakes with M≥ 6.0.
    Description: Published
    Description: 892-906
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: moment tensor ; velocity models ; strong-motion ; 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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  • 2
    Publication Date: 2017-04-04
    Description: We describe the automatic (AUTO) and the reviewed (REV) seismic time-domain moment tensor (TDMT) procedures implemented recently at the Istituto Nazionale di Geofisica e Vulcanologia (INGV), Italy. The solutions are obtained from the high-quality data of the recently installed Italian broadband network and of the Mediterranean seismographic network (MedNet). AUTO- and REV-TDMT adopt the long-period full waveform inversion code developed by Dreger and Helmberger (1993). AUTO-TDMT is triggered by local and regional events with magnitude ML 〉=3.5 detected by the INGV seismic center. Moment tensor solutions are available within about 10 min after earthquake location, and they are automatically published on the World Wide Web for solution qualities exceeding a predefined threshold. REV-TDMT solutions are posted on the World Wide Web and included in the INGV-TDMT catalog after manual revision. The catalog we describe has great potential to improve our understanding of the regional seismicity and of the ongoing tectonics because the TDMT solutions are the only moment tensors and moment magnitudes released for Italy for many of the events with ML 〈=4.2.
    Description: This work has been funded by the 2005–2007 DPC-S4 and 2008–2010 DPC-S3 Italian Civil Protection contracts.
    Description: Published
    Description: 2223-2242
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: moment tensor ; 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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  • 3
    Publication Date: 2017-04-04
    Description: The 31 October and 1 November 2002, Molise earthquakes (both MW 5.7) were caused by right-lateral slip between 12 and 20 km depth. These earthquakes are the result of large-scale reactivation of pre-existing, left-lateral, regionally extended E-W structures of Mesozoic age. Although recorded ground motions were generally smaller than expected for typical Italian earthquakes, a recent paper attributes a stress drop as high as 180 bars to the Molise earthquakes. We remark that a high stress drop is in contrast both with the relatively long source duration inferred in previous investigations and with geodetic evidence for a significantly smaller fault slip compared with other Apennines earthquakes having similarly large rupture area (e.g. 1997 Umbria-Marche earthquakes). We analyzed both ground acceleration spectra of the mainshocks and single-station spectral ratios of broad-band seismograms in an extended magnitude range (2.7 ≤ MW ≤ 5.7). Our results show that neither the spectral amplitudes of recorded ground motions nor the spectral ratios can be fit by a high stress drop source. Instead we find that the observations are consistent with a low stress drop, our best estimates ranging between 6 and 25 bars, in agreement with the relatively long source duration and small coseismic slip. We interpret the low stress of the 2002 Molise earthquakes in terms of lower energy release mechanisms due to the reutilization of faults reactivated opposite to their original sense of slip.
    Description: Published
    Description: 307-324
    Description: 4.2. TTC - Modelli per la stima della pericolosità sismica a scala nazionale
    Description: JCR Journal
    Description: partially_open
    Keywords: stress drop ; 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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  • 4
    Publication Date: 2017-04-04
    Description: The introduction of the linear slip–weakening friction law permits the solution of the elasto–dynamic equation for a rupture which develops on a fault, by removing the singularity in the components of stress tensor, thereby ensuring a finite energy flux at the crack tip. With this governing model, largely used by seismologists, it is possible to simulate a single earthquake event but, in absence of remote tectonic loading, it requires the introduction of an artificial procedure to initiate the rupture, i.e, to reach the failure stress point. In this paper, by studying the dynamic rupture propagation and the solutions on the fault and on the free surface, we systematically compare three conceptually and algorithmically different nucleation strategies widely adopted in the literature: the imposition of an initially constant rupture speed, the introduction of a shear stress asperity, and the perturbation to the initial particle velocity field. Our results show that, contrarily to supershear ruptures which tend to “forget” their origins, subshear ruptures are quite sensitive to the adopted nucleation procedure, which can bias the runaway rupture. We confirm that that the most gradual transition from imposed nucleation and spontaneous propagation is obtained by initially forcing the rupture to expand at a properly chosen, constant speed (0.75 times the Rayleigh speed). We also numerically demonstrate that a valid alternative to this strategy is an appropriately smoothed, elliptical shear stress asperity. Moreover, we evaluate the optimal size of the nucleation patch where the procedure is applied; our simulations indicate that its size has to equal the critical distance of Day (1982) in case of supershear ruptures and to exceed it in case of subshear ruptures.
    Description: In press
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: open
    Keywords: Nucleation strategies ; 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: 2017-04-04
    Description: This study investigates the engineering applicability of two conceptually different finite-fault simulation techniques. We focus our attention on two important aspects: first to quantify the capability of the methods to reproduce the observed ground-motion parameters (peaks and integral quantities); second to quantify the dependence of the strong-motion parameters on the variability in the large-scale kinematic definition of the source (i.e., position of the nucleation point, value of the rupture velocity, and distribution of the final slip on the fault). We applied an approximated simulation technique, the deterministic-stochastic method and a broadband technique, the hybrid-integral-composite method, to model the 1984 Mw 5.7 Gubbio, central Italy, earthquake, at five accelerometric stations. We first optimize the position of the nucleation point and the value of the rupture velocity for three different final slip distributions on the fault by minimizing an error function in terms of acceleration response spectra in the frequency band from 1 to 9 Hz. We found that the best model is given by a rupture propagating at about 2:65 km=sec from a hypocenter located approximately at the center of the fault. In the second part of the article we calculate more than 2400 scenarios varying the kinematic source parameters. At the five sites we compute the residuals distributions for the various strongmotion parameters and show that their standard deviations depend on the source parameterization adopted by the two techniques. Furthermore, we show that Arias Intensity (AI) and significant duration are characterized by the largest and smallest standard deviation, respectively. Housner Intensity is better modeled and less affected by uncertainties in the source kinematic parameters than AI. The fact that the uncertainties in the kinematic model affects the variability of different ground-motion parameters in different ways has to be taken into account when performing hazard assessment and earthquake engineering studies for future events.
    Description: Published
    Description: 647-663
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: reserved
    Keywords: ground-motion simulation ; Gubbio 1984 ; ground-motion variability ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
    Publication Date: 2017-04-04
    Description: The introduction of the linear slip–weakening friction law permits the solution of the elasto–dynamic equation for a rupture which develops on a fault, by removing the singularity in the components of stress tensor, thereby ensuring a finite energy flux at the crack tip. With this governing model, largely used by seismologists, it is possible to simulate a single earthquake event but, in absence of remote tectonic loading, it requires the introduction of an artificial procedure to initiate the rupture, i.e, to reach the failure stress point. In this paper, by studying the dynamic rupture propagation and the solutions on the fault and on the free surface, we systematically compare three conceptually and algorithmically different nucleation strategies widely adopted in the literature: the imposition of an initially constant rupture speed, the introduction of a shear stress asperity, and the perturbation to the initial particle velocity field. Our results show that, contrarily to supershear ruptures which tend to “forget” their origins, subshear ruptures are quite sensitive to the adopted nucleation procedure, which can bias the runaway rupture. We confirm that that the most gradual transition from imposed nucleation and spontaneous propagation is obtained by initially forcing the rupture to expand at a properly chosen, constant speed (0.75 times the Rayleigh speed). We also numerically demonstrate that a valid alternative to this strategy is an appropriately smoothed, elliptical shear stress asperity. Moreover, we evaluate the optimal size of the nucleation patch where the procedure is applied; our simulations indicate that its size has to equal the critical distance of Day (1982) in case of supershear ruptures and to exceed it in case of subshear ruptures.
    Description: Published
    Description: 923–940
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Earthquake nucleation ; Computational seismology ; 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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  • 7
    Publication Date: 2017-04-04
    Description: In 1966, the Istituto Internazionale di Vulcanologia (I.I.V.), gave the go ahead to the ambitious project of setting up a seismic network in the southern Tyrrhenian Sea, an area of extraordinary geophysical interest, which until then was not covered by seismic monitoring. At the time, there were single seismic stations on the rest of the italian peninsula. These were inside universities, public and private bodies and at the numerous observatories of the Istituto Nazionale di Geofisica (founded in 1936 by Antonino Lo Surdo and becoming independent of the Consiglio Nazionale delle Ricerche (C.N.R,. in 1945) and still used mechanical seismographs, with masses weighing from 80 up to 1300 Kg. On the Aeolian Islands instead, electromagnetic seismometers were employed from the start. The experimental network, planned in the Willmore laboratories at Edinburgh and tested in the Aeolian Islands over a two-year period, represented the starting point for the Permanent Seismic Network (PSN) of the Southern Tyrrhenian. After the experience of the Laboratorio Internazionale per le Ricerche Vulcanologiche (L.I.R.V. - C.N.R.), of the Istituto di Vulcanologia of the University of Catania, the independent I.I.V. - C.N.R., together with the observatory, was launched in 1969. In the course of the seventies, every island of the Aeolian archipelago, was equipped with at least a seismic station and the 3 sensor systems (triaxial systems) began to become widely used. In the eighties, the “Sismologia Eolie” project was started, aimed at a further develop and update the seismic net. With the wide use of magnetic tape recording, the instrumental data stored could be more readily transported on suitable drums to the main centre in Catania for analysis. Here, Research Units were established in order to prepare the way for enhanced interaction between technical staff and research groups. The instrumental geophysical investigations, progressively extended and in a permanente form to Eastern Sicily and particular around Etna. From the nineties, operations room in Catania was fully active, working 24/24, and ensuring the seismic and volcanic surveillance of Etna, Stromboli and Vulcano. The Geophysical Observatory of Lipari and the main centre of the Institute in Catania, were merged in 2001 into the new Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the network of the Aeolian Islands became an integral part of the Permanent Seismic Network (PSN) of Eastern Sicily and Southern Calabria. Special prominence will be given in the course of this historical reconstruction to the evolution of instrumental seismology, thanks to forty years of continuous input, indispensable for the understanding of the seismogenetic processes in the area, this still represents the chief undertaking of the geophysical observatory on Lipari, whose important scientific but also social role must be acknowledged in the growing interaction between research and civil protection.
    Description: Published
    Description: 1-40
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: N/A or not JCR
    Description: open
    Keywords: L'Osservatorio Geofisico di Lipari ; 04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
    Publication Date: 2017-04-04
    Description: In this paper, we adopt three ground-motion simulation techniques (EXSIM, Motazedian and Atkinson, 2005, DSM, Pacor et al., 2005 and HIC, Gallovič and Brokešová, 2007), with the aim of investigating the different performances in near-fault strong-motion modeling and prediction from past and future events. The test case is the 1980, M 6.9, Irpinia earthquake, the strongest event recorded in Italy. First, we simulate the recorded strong-motion data and validate the model parameters by computing spectral acceleration and peak amplitudes residual distributions. The validated model is then used to investigate the influence of site effects and to compute synthetic ground motions around the fault. Afterward, we simulate the expected ground motions from scenario events on the Irpinia fault, varying the hypocenters, the rupture velocities and the slip distributions. We compare the median ground motions and related standard deviations from all scenario events with empirical ground motion prediction equations (GMPEs). The synthetic median values are included in the median ± one standard deviation of the considered GMPEs. Synthetic peak ground accelerations show median values smaller and with a faster decay with distance than the empirical ones. The synthetics total standard deviation is of the same order or smaller than the empirical one and it shows considerable differences from one simulation technique to another. We decomposed the total standard deviation into its between-scenario and within-scenario components. The larger contribution to the total sigma comes from the latter while the former is found to be smaller and in good agreement with empirical inter-event variability.
    Description: In press
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: restricted
    Keywords: Irpinia 1980 earthquake ; ground-motion simulation ; ground-motion variability ; scenario events ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 9
    Publication Date: 2017-04-04
    Description: In questo lavoro viene descritto il complesso sistema di acquisizione dati della RSM [vedi D’Alema et al., 2011 - in questo volume], costituita da 58 stazioni collegate in tempo reale e 13 stazioni dial-up. I dati delle stazioni in tempo reale sono acquisiti con il programma Seiscomp31; la detezione degli eventi sismici viene eseguita con il programma Earthworm ed infine l’analisi e l’interpretazione degli eventi viene effettuata attraverso il programma SacPicker di Daniele Spallarossa [vedi Spallarossa, 2011 - in questo volume]. La parte di rete dial-up è basata sul sistema Lennartz Mars882 ed è configurata in modo autonomo dalla rete in tempo reale. I dati delle due reti vengono successivamente uniti in un unico dataset ai fini di una interpretazione interattiva congiunta.
    Description: Published
    Description: 124-127
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: N/A or not JCR
    Description: open
    Keywords: rete sismica ; ancona ; acquisizione dati ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
    Publication Date: 2017-04-04
    Description: Da alcuni anni l’INGV e la Regione Marche collaborano nell’azione di monitoraggio sismico del territorio regionale. Nella sede di Ancona del CNT sono acquisiti in tempo reale i segnali sismici di circa 80 stazioni dell’Italia centro-orientale. Si è reso pertanto necessario sviluppare applicativi utili al controllo degli apparati che compongono il sistema di monitoraggio. In particolare, vengono controllati: 1) lo stato di funzionamento delle trasmissioni radio ed ethernet; 2) lo stato dell’alimentazione delle stazioni e il numero di satelliti ricevuti dagli apparati GPS; 3) la quantità di segnale sismico archiviato e i gaps del segnale continuo; 4) i livelli di rumore di fondo e la qualità del segnale sismico.
    Description: Published
    Description: 104-107
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: N/A or not JCR
    Description: open
    Keywords: rete sismica ; ancona ; centro acquisizione ; telecomunicazioni ; qualità segnali ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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