Laura Peruzza | Istituto Nazionale di Oceanografia e Geofisica Sperimentale (original) (raw)
Papers by Laura Peruzza
Bulletin of Earthquake Engineering, 2016
A procedure is here proposed to score probabilistic seismic hazard estimates provided by ergodic ... more A procedure is here proposed to score probabilistic seismic hazard estimates provided by ergodic models by a comparison with accelerometric observations available during a control period. The procedure allows accounting for the potential bias induced by spatial correlation of hazard estimates due to the use of ground motion prediction equations in the modeling. Since this bias depends on the specific topological features of the studied system (relative positions of seismic sources and accelerometric control sites), numerical simulations are considered to correct it. An application of the above procedure is proposed for Italy where some probabilistic seismic hazard estimates have been provided in the last years, and where 76 accelerometric sites have been operating for more than 25 years. It is shown that, at least as the case study concerns, the amount of spatial correlation in the hazard estimates is relatively weak, it depends on the GMPE used in computations and increases with the exceedance probabilities and with the period of the acceleration response spectrum.
We perform aftershock probabilistic seismic hazard analysis (APSHA) of the ongoing aftershock seq... more We perform aftershock probabilistic seismic hazard analysis (APSHA) of the ongoing aftershock sequence following the Amatrice August 24th, 2016 Central Italy earthquake. APSHA is a time-dependent PSHA calculation where earthquake occurrence rates decrease after the occurrence of a mainshock following an Omori-type decay. In this paper we propose a fault source model based on preliminary evidence of the complex fault geometry associated with the mainshock. We then explore the possibility that the aftershock seismicity is distributed either uniformly or non-uniformly across the fault source. The hazard results are then computed for short-intermediate exposure periods (1-3 months, 1 year). They are compared to the background hazard and intended to be useful for post-earthquake safety evaluation.
We perform a series of sensitivity tests showing the impact of fault geometry, GMPE, seismicity d... more We perform a series of sensitivity tests showing the impact of fault geometry, GMPE, seismicity distribution, and topography on the hazard results. The examples below are all computed for an exposure period of 1-year, where we assign a G-R distribution to the fault surface, which is modelled as a series of point sources (Mmin=3.5, Mmax=5.5, b=1.0). The scalar seismic moment rate of the fault is the same for each computation.
Alcune decine di copie del volume in cartaceo ancora disponibili, per fondi di archivio. Se inter... more Alcune decine di copie del volume in cartaceo ancora disponibili, per fondi di archivio.
Se interessati a riceverle, scrivere indicando motivazione e indirizzo. Rispondero' nei limiti della disponibilità
Résumé/Abstract This paper presents the results of an analysis showing the effect of different as... more Résumé/Abstract This paper presents the results of an analysis showing the effect of different assumptions of magnitude recurrence and time dependence on probabilistic seismic hazard assessment for the Abruzzo area. The focus is on alternative peak ground ...
Bulletin of the …, 2006
We defined a seismogenic model for central Italy based on three layers of sources and computed th... more We defined a seismogenic model for central Italy based on three layers of sources and computed the relative seismic-hazard maps. One layer is constituted by individual structures liable to generate major earthquakes (M Ն5.5). We defined them as seismogenic boxes by using geological information in terms of plan projection of active faults; the seismicity rates associated with an individual source are based on the geometry and kinematics of the fault; the recurrence model is controlled by the earthquake-source association, and, when possible, we defined the occurrence time of the last major event, using it in a time-dependent approach. Another layer is given by the instrumental seismicity analysis of the past two decades, which allows us to evaluate the background seismicity (M ϳϽ5.5); using a sliding-window selection of events, we defined a model of regular adjacent cells of variable a and b values of the Gutenberg-Richter relation. The last layer utilizes all the instrumental earthquakes and the historical events not correlated to known structures (4.5 Ͻ M ϳϽ6), by separating them into seismotectonic provinces shaped on a geological-structural basis. The seismic-hazard computations first use this layered model in a traditional probabilistic scheme. The results indicate a narrow belt of peak ground acceleration (PGA) higher than 0.30g (with standard deviation in attenuation functions) in the axial part of the Apennine chain, with a maximum spot of PGA Ͼ0.40g southeast of the area damaged by the 1997-1998 Umbria-Marche sequence (PGA expected not to be exceeded in 50 years at 90% probability level). The background seismicity gives a nonnegligible contribution to the hazard, at least for first damage levels. Then, a simplified time-dependent hypothesis has been introduced for the individual sources alone, computing the conditional probability of occurrence of characteristic earthquakes for each source by Brownian passage time distributions. Adopting equivalent fictitious seismicity rates, we obtained maps referring to the next 50 years by using traditional codes. These results show that the contribution of the recently active sources vanishes, and the most hazardous sites are now located south of L'Aquila and in the Sulmona area. We consider that the methodology and results obtained are useful for seismic risk reduction strategies.
Mem. Soc. Geol. Ital, 2002
In the last few years, Italy has been facing the problem of a new generation of hazard maps, with... more In the last few years, Italy has been facing the problem of a new generation of hazard maps, with the transition from standard probabilistic seismic hazard estimates to time-dependent seismic hazard assessments. These innovative methodologies require the detailed knowledge of the parameters of individual sources (seismogenic structures), so that some constraints on the seismicity characterisation, based on independent geological evidence, can be introduced.
Bulletin of Earthquake Engineering, 2011
After the April 6th 2009 L’Aquila earthquake (M w 6.3), where 306 people died and a further 60,00... more After the April 6th 2009 L’Aquila earthquake (M w 6.3), where 306 people died and a further 60,000 were displaced, seismic microzoning investigations have been carried out for towns affected by a macroseismic intensity equal to or greater than 7 MCS. Based upon seismotectonic data, historical seismicity and strong motion records, we defined input spectra to be used in the numerical simulations of seismic microzoning in four key municipalities, including the town of L’Aquila. We adopted two main approaches: uniform hazard response spectra are obtained by a probabilistic seismic hazard assessment introducing some time-dependency for individual faults on the study area; a deterministic design spectrum is computed from magnitude/distance pairs extracted by a stationary probabilistic analysis of historical intensities. The uniform hazard spectrum of the present Italian building code represents the third, less restrictive, response spectrum to be used for the numerical simulations in seismic microzoning. Strong motions recordings of the main shock of the L’Aquila sequence enlighten the critical role played by both the local response and distances metric for sites located above a seismogenic fault; however, these time-histories are compatible with the uncertainties of a deterministic utilization of ground motion predictive equations. As recordings at very near field are rare, they cannot be neglected while defining the seismic input. Disaggregation on the non-Possonian seismotectonic analysis and on the stationary site-intensity estimates reach very similar results in magnitude-distance pairs identification; we interpret this convergence as a validation of the geology-based model by historical observations.
La presente relazione descrive l’attivit`a svolta nel 2012 dall’Istituto Nazionale di Oceanografi... more La presente relazione descrive l’attivit`a svolta nel 2012 dall’Istituto Nazionale di Oceanografia e di Geofisica Sperimentale–OGS per conto della Regione Veneto nell’ambito della Convenzione n. 24106 - DGR n. 3801 del 09/12/2009 relativa alla gestione della Rete Sismometrica del Veneto (RSV), allo studio della sismicit`a regionale ed alla ricerca sismologica a fini di protezione civile. In particolare, la Convenzione prevedeva: 1. Gestione e manutenzione ordinaria e straordinaria della rete sismometrica della Regione; 2. Aggiornamento e/o riconfigurazione della rete sismometrica della Regione; 3. Realizzazione di una stazione sismometrica da porre in profondit`a in un sito di pianura reso disponibile dalla Regione; 4. Elaborazione e trasmissione automatica e in tempo reale dei dati parametrici dei terremoti di interesse per la Regione; 5. Servizio di sorveglianza, allerta, reperibilit`a e pronto intervento e supporto scientifico nel caso di evento sismico; 6. Prosecuzione dello stu...
Il Gruppo Nazionale per la Difesa dai Terremoti (GNDT) viene costituito presso il Consiglio Nazio... more Il Gruppo Nazionale per la Difesa dai Terremoti (GNDT) viene costituito presso il Consiglio Nazionale delle Ricerche (C.N.R.) con il Decreto Interministeriale del 7 luglio 1983, e riconfermato periodicamente con decreti ministeriali.
L'idea di progetto è nata nell'estate del 1999 in una situazione davvero molto particolare: (i) u... more L'idea di progetto è nata nell'estate del 1999 in una situazione davvero molto particolare: (i) un lungo periodo di ripensamento del settore della ricerca sui terremoti, seguito al terremoto umbro-marchigiano del 1997-1998; (ii) il nostro ente (GNDT -Gruppo Nazionale per la Difesa dai Terremoti) in crisi pesante e commissariato; (iii) al suo interno un gruppo di ricercatori precari (mediamente da oltre 10 anni) decisamente a rischio; (iv) sullo sfondo l'imminente nascita dell'INGV.
A seguito della crisi sismica che ha devastato L'Aquila, dalla fine di maggio 2009 OGS e Universi... more A seguito della crisi sismica che ha devastato L'Aquila, dalla fine di maggio 2009 OGS e Università di Chieti hanno installato una piccola rete sismometrica locale composta da 6 stazioni temporanee configurate per la registrazione in continuo. La distanza media tra le stazioni (di 10-15 km) e la geometria di rete (che attualmente utilizza anche i dati di due stazioni INGV e che a breve integrerà le osservazioni delle stazioni della Rete Abruzzese triggerate) consentono di individuare e localizzare, nell'area del bacino di Sulmona, a ovest del Massiccio della Maiella, eventi sismici finora non rilevati dalla Rete Sismica Nazionale Centralizzata.
An empirical scoring test on PSHA in Italy has been realized in the frame of the Project S2-2012 ... more An empirical scoring test on PSHA in Italy has been realized in the frame of the Project S2-2012 (https://sites.google.com/site/ingvdpc2012progettos2/home), the first annual phase of researches funded by the 2012-2021 Agreement between the National Civil Defence Department (DPC) and National Institute of Geophysics and Volcanology (INGV). The test is based on the comparison of outcomes provided by ten time-independent hazard models at about 70 accelerometric sites in Italy, characterized by a long recording history (>25 years). Maxima observed Peak Ground Accelerations (PGA) in a control period have been compared with the hazard estimates, after that a site-specific correction has been applied accordingly to the Italian and European regulations. In particular, by considering a control period of 25 years, we compared the number of sites where reference PGA values (i.e., the PGA values characterized by a given exceedance probability) have been empirically exceeded, with the one expected on the basis of the relevant hazard model. This comparison allows scoring the most effective computational models and identifying those providing outcomes in contrast with observations, that should therefore be discarded. The analysis shows that most of hazard estimates so far proposed for Italy are not in contrast with observations gathered in the 1979-2004; some models, however, perform significantly better than the others do, but the same computational scheme can perform very differently, depending on the region considered and on the average return time analysed. The models collected span about 20 years of PSHA practice in Italy and Europe; not necessarily the most recent models perform better than the older ones. The site-specific characterization of accelerometric stations is a critical element for which additional studies should been planned in the future.
Bulletin of Earthquake Engineering, 2016
A procedure is here proposed to score probabilistic seismic hazard estimates provided by ergodic ... more A procedure is here proposed to score probabilistic seismic hazard estimates provided by ergodic models by a comparison with accelerometric observations available during a control period. The procedure allows accounting for the potential bias induced by spatial correlation of hazard estimates due to the use of ground motion prediction equations in the modeling. Since this bias depends on the specific topological features of the studied system (relative positions of seismic sources and accelerometric control sites), numerical simulations are considered to correct it. An application of the above procedure is proposed for Italy where some probabilistic seismic hazard estimates have been provided in the last years, and where 76 accelerometric sites have been operating for more than 25 years. It is shown that, at least as the case study concerns, the amount of spatial correlation in the hazard estimates is relatively weak, it depends on the GMPE used in computations and increases with the exceedance probabilities and with the period of the acceleration response spectrum.
We perform aftershock probabilistic seismic hazard analysis (APSHA) of the ongoing aftershock seq... more We perform aftershock probabilistic seismic hazard analysis (APSHA) of the ongoing aftershock sequence following the Amatrice August 24th, 2016 Central Italy earthquake. APSHA is a time-dependent PSHA calculation where earthquake occurrence rates decrease after the occurrence of a mainshock following an Omori-type decay. In this paper we propose a fault source model based on preliminary evidence of the complex fault geometry associated with the mainshock. We then explore the possibility that the aftershock seismicity is distributed either uniformly or non-uniformly across the fault source. The hazard results are then computed for short-intermediate exposure periods (1-3 months, 1 year). They are compared to the background hazard and intended to be useful for post-earthquake safety evaluation.
We perform a series of sensitivity tests showing the impact of fault geometry, GMPE, seismicity d... more We perform a series of sensitivity tests showing the impact of fault geometry, GMPE, seismicity distribution, and topography on the hazard results. The examples below are all computed for an exposure period of 1-year, where we assign a G-R distribution to the fault surface, which is modelled as a series of point sources (Mmin=3.5, Mmax=5.5, b=1.0). The scalar seismic moment rate of the fault is the same for each computation.
Alcune decine di copie del volume in cartaceo ancora disponibili, per fondi di archivio. Se inter... more Alcune decine di copie del volume in cartaceo ancora disponibili, per fondi di archivio.
Se interessati a riceverle, scrivere indicando motivazione e indirizzo. Rispondero' nei limiti della disponibilità
Résumé/Abstract This paper presents the results of an analysis showing the effect of different as... more Résumé/Abstract This paper presents the results of an analysis showing the effect of different assumptions of magnitude recurrence and time dependence on probabilistic seismic hazard assessment for the Abruzzo area. The focus is on alternative peak ground ...
Bulletin of the …, 2006
We defined a seismogenic model for central Italy based on three layers of sources and computed th... more We defined a seismogenic model for central Italy based on three layers of sources and computed the relative seismic-hazard maps. One layer is constituted by individual structures liable to generate major earthquakes (M Ն5.5). We defined them as seismogenic boxes by using geological information in terms of plan projection of active faults; the seismicity rates associated with an individual source are based on the geometry and kinematics of the fault; the recurrence model is controlled by the earthquake-source association, and, when possible, we defined the occurrence time of the last major event, using it in a time-dependent approach. Another layer is given by the instrumental seismicity analysis of the past two decades, which allows us to evaluate the background seismicity (M ϳϽ5.5); using a sliding-window selection of events, we defined a model of regular adjacent cells of variable a and b values of the Gutenberg-Richter relation. The last layer utilizes all the instrumental earthquakes and the historical events not correlated to known structures (4.5 Ͻ M ϳϽ6), by separating them into seismotectonic provinces shaped on a geological-structural basis. The seismic-hazard computations first use this layered model in a traditional probabilistic scheme. The results indicate a narrow belt of peak ground acceleration (PGA) higher than 0.30g (with standard deviation in attenuation functions) in the axial part of the Apennine chain, with a maximum spot of PGA Ͼ0.40g southeast of the area damaged by the 1997-1998 Umbria-Marche sequence (PGA expected not to be exceeded in 50 years at 90% probability level). The background seismicity gives a nonnegligible contribution to the hazard, at least for first damage levels. Then, a simplified time-dependent hypothesis has been introduced for the individual sources alone, computing the conditional probability of occurrence of characteristic earthquakes for each source by Brownian passage time distributions. Adopting equivalent fictitious seismicity rates, we obtained maps referring to the next 50 years by using traditional codes. These results show that the contribution of the recently active sources vanishes, and the most hazardous sites are now located south of L'Aquila and in the Sulmona area. We consider that the methodology and results obtained are useful for seismic risk reduction strategies.
Mem. Soc. Geol. Ital, 2002
In the last few years, Italy has been facing the problem of a new generation of hazard maps, with... more In the last few years, Italy has been facing the problem of a new generation of hazard maps, with the transition from standard probabilistic seismic hazard estimates to time-dependent seismic hazard assessments. These innovative methodologies require the detailed knowledge of the parameters of individual sources (seismogenic structures), so that some constraints on the seismicity characterisation, based on independent geological evidence, can be introduced.
Bulletin of Earthquake Engineering, 2011
After the April 6th 2009 L’Aquila earthquake (M w 6.3), where 306 people died and a further 60,00... more After the April 6th 2009 L’Aquila earthquake (M w 6.3), where 306 people died and a further 60,000 were displaced, seismic microzoning investigations have been carried out for towns affected by a macroseismic intensity equal to or greater than 7 MCS. Based upon seismotectonic data, historical seismicity and strong motion records, we defined input spectra to be used in the numerical simulations of seismic microzoning in four key municipalities, including the town of L’Aquila. We adopted two main approaches: uniform hazard response spectra are obtained by a probabilistic seismic hazard assessment introducing some time-dependency for individual faults on the study area; a deterministic design spectrum is computed from magnitude/distance pairs extracted by a stationary probabilistic analysis of historical intensities. The uniform hazard spectrum of the present Italian building code represents the third, less restrictive, response spectrum to be used for the numerical simulations in seismic microzoning. Strong motions recordings of the main shock of the L’Aquila sequence enlighten the critical role played by both the local response and distances metric for sites located above a seismogenic fault; however, these time-histories are compatible with the uncertainties of a deterministic utilization of ground motion predictive equations. As recordings at very near field are rare, they cannot be neglected while defining the seismic input. Disaggregation on the non-Possonian seismotectonic analysis and on the stationary site-intensity estimates reach very similar results in magnitude-distance pairs identification; we interpret this convergence as a validation of the geology-based model by historical observations.
La presente relazione descrive l’attivit`a svolta nel 2012 dall’Istituto Nazionale di Oceanografi... more La presente relazione descrive l’attivit`a svolta nel 2012 dall’Istituto Nazionale di Oceanografia e di Geofisica Sperimentale–OGS per conto della Regione Veneto nell’ambito della Convenzione n. 24106 - DGR n. 3801 del 09/12/2009 relativa alla gestione della Rete Sismometrica del Veneto (RSV), allo studio della sismicit`a regionale ed alla ricerca sismologica a fini di protezione civile. In particolare, la Convenzione prevedeva: 1. Gestione e manutenzione ordinaria e straordinaria della rete sismometrica della Regione; 2. Aggiornamento e/o riconfigurazione della rete sismometrica della Regione; 3. Realizzazione di una stazione sismometrica da porre in profondit`a in un sito di pianura reso disponibile dalla Regione; 4. Elaborazione e trasmissione automatica e in tempo reale dei dati parametrici dei terremoti di interesse per la Regione; 5. Servizio di sorveglianza, allerta, reperibilit`a e pronto intervento e supporto scientifico nel caso di evento sismico; 6. Prosecuzione dello stu...
Il Gruppo Nazionale per la Difesa dai Terremoti (GNDT) viene costituito presso il Consiglio Nazio... more Il Gruppo Nazionale per la Difesa dai Terremoti (GNDT) viene costituito presso il Consiglio Nazionale delle Ricerche (C.N.R.) con il Decreto Interministeriale del 7 luglio 1983, e riconfermato periodicamente con decreti ministeriali.
L'idea di progetto è nata nell'estate del 1999 in una situazione davvero molto particolare: (i) u... more L'idea di progetto è nata nell'estate del 1999 in una situazione davvero molto particolare: (i) un lungo periodo di ripensamento del settore della ricerca sui terremoti, seguito al terremoto umbro-marchigiano del 1997-1998; (ii) il nostro ente (GNDT -Gruppo Nazionale per la Difesa dai Terremoti) in crisi pesante e commissariato; (iii) al suo interno un gruppo di ricercatori precari (mediamente da oltre 10 anni) decisamente a rischio; (iv) sullo sfondo l'imminente nascita dell'INGV.
A seguito della crisi sismica che ha devastato L'Aquila, dalla fine di maggio 2009 OGS e Universi... more A seguito della crisi sismica che ha devastato L'Aquila, dalla fine di maggio 2009 OGS e Università di Chieti hanno installato una piccola rete sismometrica locale composta da 6 stazioni temporanee configurate per la registrazione in continuo. La distanza media tra le stazioni (di 10-15 km) e la geometria di rete (che attualmente utilizza anche i dati di due stazioni INGV e che a breve integrerà le osservazioni delle stazioni della Rete Abruzzese triggerate) consentono di individuare e localizzare, nell'area del bacino di Sulmona, a ovest del Massiccio della Maiella, eventi sismici finora non rilevati dalla Rete Sismica Nazionale Centralizzata.
An empirical scoring test on PSHA in Italy has been realized in the frame of the Project S2-2012 ... more An empirical scoring test on PSHA in Italy has been realized in the frame of the Project S2-2012 (https://sites.google.com/site/ingvdpc2012progettos2/home), the first annual phase of researches funded by the 2012-2021 Agreement between the National Civil Defence Department (DPC) and National Institute of Geophysics and Volcanology (INGV). The test is based on the comparison of outcomes provided by ten time-independent hazard models at about 70 accelerometric sites in Italy, characterized by a long recording history (>25 years). Maxima observed Peak Ground Accelerations (PGA) in a control period have been compared with the hazard estimates, after that a site-specific correction has been applied accordingly to the Italian and European regulations. In particular, by considering a control period of 25 years, we compared the number of sites where reference PGA values (i.e., the PGA values characterized by a given exceedance probability) have been empirically exceeded, with the one expected on the basis of the relevant hazard model. This comparison allows scoring the most effective computational models and identifying those providing outcomes in contrast with observations, that should therefore be discarded. The analysis shows that most of hazard estimates so far proposed for Italy are not in contrast with observations gathered in the 1979-2004; some models, however, perform significantly better than the others do, but the same computational scheme can perform very differently, depending on the region considered and on the average return time analysed. The models collected span about 20 years of PSHA practice in Italy and Europe; not necessarily the most recent models perform better than the older ones. The site-specific characterization of accelerometric stations is a critical element for which additional studies should been planned in the future.