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Console, Rodolfo
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- PublicationOpen AccessImplications of earthquake recurrence models to the seismic hazard estimates in the marmara region, Turkey(2014)
; ; ; ; ; ; ; ;; In this study, we show the effect of time-independent and time-dependent occurrence models on the seismic hazard estimations. The time-dependency is introduced by 1) the Brownian Passage Time (BPT) probability model that is based on a simple physical model of the earthquake cycle 2) the fusion of the BPT renewal model (BPT+ΔCFF) with a physical model that considers the earthquake probability perturbation for interacting faults by static Coulomb stress changes. To do so, we calculate the probability of occurrence of earthquakes Mw > 6.5 for individual fault sources in the Marmara region for the 5-10-30 and 50-year periods (starting from January 1, 2013). We treat the uncertainties in the fault parameters (e.g. slip rate, characteristic magnitude and aperiodicity) of the statistical distribution associated to each examined fault source by a Monte Carlo technique. Then the probabilities of occurrence for the next characteristic earthquake are calculated from three different models (Poisson, BPT, and BPT+ΔCFF) considering the 10th, 50th and 90th percentiles of the Monte Carlo distribution. In order to evaluate the impact of the earthquake probability models to ground motion hazard we attempt to calculate the fault-based probabilistic seismic hazard maps (PSHA) of mean Peak Ground Acceleration (PGA) having 10% probability of exceedance in 50 years on rock site condition. We note that in the present study we did not take in to account the ground motion variability caused by the different GMPE choices. In fact only one GMPE model is chosen as defined by Akkar and Cagnan (2010) (hereafter, AC10) for the active shallow crustal region for assessing the ground shaking hazard in the Marmara region in order to avoid those variability’s effect the final seismic hazard estimations in the study region. We observed that the impact of the different occurrence models on the seismic hazard estimate of selected sites is quite high: the hazard may increase by more than 70% or decrease by as much as 70%, depending on the applied model. We demonstrated that the estimated average recurrence time and the associated magnitude together with the elapsed time are crucial parameters in the earthquake probability calculations.768 101 - PublicationRestrictedPhysics-Based Simulation of Spatiotemporal Patterns of Earthquakes in the Corinth Gulf, Greece, Fault System(2022)
; ; ; ; ; ; ; ; ; A physics-based earthquake simulation algorithm for modeling the long-term spatiotemporal process of strong (M ≥ 6.0) earthquakes in Corinth Gulf area, Greece, is employed and its performance is explored. The underlying physical model includes the rate- and state-dependent frictional formulation, along with the slow tectonic loading and coseismic static stress transfer. The study area constitutes a rapidly extending rift about 100 km long, where the deformation is taken up by eight major fault segments aligned along its southern coastline, and which is associated with several strong (M ≥ 6.0) earthquakes in the last three centuries, since when the historical earthquake catalog is complete. The recurrence time of these earthquakes and their spatial relation are studied, and the simulator results reveal spatiotemporal properties of the regional seismicity such as pseudoperiodicity as well as multisegment ruptures of strong earthquakes. As the simulator algorithm allows the display of the stress pattern on all the single elements of the fault, we are focusing on the time evolution of the stress level before, during, and after these earthquakes occur. In this respect, the spatiotemporal variation of the stress and its heterogeneity appear to be correlated with the process of preparation of strong earthquakes in a quantitative way.147 2 - PublicationRestrictedRelocation of Earthquakes by Source‐Specific Station Corrections in Iran(2015-09)
; ; ; ; ; ; ; ; ;Accurate earthquake locations are crucial for investigating seismogenic processes, as well as for applications like verifying compliance to the Comprehensive Nuclear‐Test‐Ban Treaty. Modeling errors of calculated travel times, in addition to the density of the stations, their epicentral distances, and their azimuthal coverage, may have the effect of shifting the computed epicenters far from the real locations, regardless of the accuracy in picking seismic phase arrivals. In the present study, we compare the regional locations for one set of earthquakes obtained by arrival times reported by the Iranian Seismological Center with teleseismic locations obtained by arrival times reported by the International Seismological Center. We found location differences on the order of 10–20 km or larger, affecting both epicentral coordinates and depths. Average travel‐time residuals to each station of the global network were computed for a set of sources located in the study area. We show that systematic shifts of hypocentral coordinates, as well as the sizes of their error ellipses, can be substantially reduced by applying source‐specific station corrections. Finally, the validity of the calibration method was confirmed by a test carried out on a dataset different from that used for computing the travel‐time corrections. This study includes an analysis of the effect of removing arrival times of critical stations from the dataset used for the locations, showing that this effect is largely reduced by the application of travel‐time corrections.475 29 - PublicationRestrictedForeshock statistics and their possible relationship to earthquake prediction in the italian regionThis study focuses on the foreshocks of earthquake sequences recorded by the Italian national seismological network between 1975 and 1991. We consider as foreshocks events exceeding a given threshold magnitude that follow a period of quiescence and come before a mainshock occurring within a given time-distance range. The total number of potential foreshocks identified by the algorithm depends on the size and the duration of the predefined quiescence area, whereas the number of mainshocks preceded by foreshocks depends also on the size of the area in which the event is expected and the duration of the alarm period. Our aim was to optimize the choice of the parameters defining potential foreshocks as precursors of stronger earthquakes, in order to improve their validity and reliability. A preliminary investigation carried over the whole Italian territory allowed the definition of zones where foreshocks-mainshocks series are likely to occur. One of these zones is an area of about 32,000 km^2 in Central Italy including a total of 2671 events of M >= 2.5, where there is a significant tendency of moderate shocks to be followed at short distance and in short time by larger shocks. Our method would lead to issuing 63 alarms with the optimal definition of foreshocks as events of magnitude exceeding 3.0 after at least 80 days of quiescence in an area of 140 km radius. The rate of occurrence for mainshocks of magnitude exceeding 4.0 during the following 48 hours, in the specified area of 30 km radius, is 6 of 23 events. The corresponding probability gain is about 150. For comparison, another larger zone (Po Valley) with 453 events of M >= 2.5 exhibits only a rate of I of 82 precursors. In this area most events are single shocks. Our analysis shows that the foreshock activity can be regarded as a significant earthquake precursor, so suggesting that real time observation of seismicity can be used to improve the quality of an earthquake prediction system.
83 4 - PublicationOpen AccessTemporal Variations of Seismicity Rates and Gutenberg–Richterb-Values for a Stochastic Declustered Catalog: An Example in Central Italy(2023)
; ; ; ; ; ; ; ;; ; ; ; ; One important aspect of the seismicity is the spatiotemporal clustering; hence, the distinction between independent and triggered events is a critical part of the analysis of seismic catalogs. Stochastic declustering of seismicity allows a probabilistic distinction between these two kinds of events. Such an approach, usually performed with the epidemic‐type aftershock sequence (ETAS) model, avoids the bias in the estimation of the frequency–magnitude distribution parameters if we consider a subset of the catalog, that is, only the independent or the triggered events. In this article, we present a framework to properly include the probabilities of any event to be independent (or triggered) both in the temporal variation of the seismic rates and in the estimation of the b‐value of the Gutenberg–Richter law. This framework is then applied to a high‐definition seismic catalog in the central part of Italy covering the period from April 2010 to December 2015. The results of our analysis show that the seismic activity from the beginning of the catalog to March 2013 is characterized by a low degree of clustering and a relatively high b‐value, whereas the following period exhibits a higher degree of clustering and a smaller b‐value.52 73 - PublicationOpen AccessApplication of an ensemble earthquake rate model in Italy, considering seismic catalogs and fault moment release(2020)
; ; ; ; ; ; ; We develop an ensemble earthquake rate model that provides spatially variable time-independent (Poisson) long-term annual occurrence rates of seismic events throughout Italy, for magnitude bin of 0.1 units from Mw ≥4.5 in spatial cells of 0.1° x 0.1°. We weighed seismic activity rates of smoothed seismicity and fault-based inputs to build our earthquake rupture forecast model, merging it into a single ensemble model. Both inputs adopt a tapered Gutenberg-Richter relation with a single b-value and a single corner magnitude estimated by earthquakes catalog. The spatial smoothed seismicity was obtained using the classical kernel smoothing method with the inclusion of magnitude dependent completeness periods applied to the Historical (CPTI15) and Instrumental seismic catalogs. For each seismogenic source provided by the Database of the Individual Seismogenic Sources (DISS), we computed the annual rate of the events above Mw4.5, assuming that the seismic moments of the earthquakes generated by each fault are distributed according to the tapered Gutenberg-Richter relation with the same parameters of the smoothed seismicity models. Comparing seismic annual rates of the catalogs with those of the seismogenic sources, we realized that there is a good agreement between these rates in Central Apennines zones, whereas the seismogenic rates are higher than those of the catalogs in the north east and south of Italy. We also tested our model against the strong Italian earthquakes (Mw5.5+), in order to check if the total number (N-test) and the spatial distribution (S-test) of these events was compatible with our model, obtaining good results, i.e. high p-values in the test. The final model will be a branch of the new Italian seismic hazard map.259 112 - PublicationOpen AccessNew insights on seismicity pattern in the Lucanian Apennines (Southern Italy) and minimum 1D velocity model(2007-04-15)
; ; ; ; ; ;Maggi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Cimini, G. B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Console, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Frepoli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; We analyzed the seismicity of Southern Italy in the area including Lucanian Apennines and Bradano foredeep, making use of the most recent seismological data base available so far. We re-picked P- and S-wave arrival times recorded by the Italian National Seismic Network (RSNC), operated by the Istituto Nazionale di Geofisica e Vulcanologia (INGV), the SAPTEX temporary array (2001-2004), and the local Eni-Agip seismic network located in the upper Agri Valley. We examined the seismicity of this area in the period between 2001 and 2006, considering events that have magnitudes greater than 2.0. Firstly, we computed the VP /VS ratio using a modified Wadati method, obtaining a value of 1.83. Secondly, through the use of the Velest code, we carried out an analysis for the one-dimensional (1D) velocity model that approximates the seismic structure of the study area. We relocated the earthquakes and for well recorded events we also computed the focal mechanisms. The denser station coverage allows us to obtain improved hypocenters with respect to those obtained by using only RSNC data. The distribution of events shows two main different domains: the westernmost characterizing the chain, mostly with shallow earthquakes, and the easternmost below the Bradano foredeep, with deeper seismicity. Fault-plane solutions were used for stress inversion. The results of this analysis are consistent with the hypothesis that the Lucanian Apennines is generally characterized by NE-SW extension.166 628 - PublicationOpen AccessTRAVEL-TIME SOURCE SPECIFIC STATION CORRECTION IMPROVES LOCATION ACCURACY(CTBTO, 2013-06-17)
; ; ; ; ; ; ;Alessandra, Giuntini; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Valerio, Materni; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Stefano, Chiappini; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Roberto, Carluccio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Rodolfo, Console ;Massimo, Chiappini; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ; ; ;; CTBTOAccurate earthquake locations are crucial for investigating seismogenic processes, as well as for applications like verifying compliance to the Comprehensive Test Ban Treaty (CTBT). Earthquake location accuracy is related to the degree of knowledge about the 3-D structure of seismic wave velocity in the Earth. It is well known that modeling errors of calculated travel times may have the effect of shifting the computed epicenters far from the real locations by a distance even larger than the size of the statistical error ellipses, regardless of the accuracy in picking seismic phase arrivals. We have developed a method of seismic location to minimize this systematic shifts affecting hypocentral locations. These method is based on the fact that such shifts are quite similar for events for which the hypocenters are close to each other with respect to their distance from the recording stations. So this method is based on a set of Ground Truth events recorded by a dense local seismic network in seismically active regions. The applications concern seismic sequences recorded in Italy and Iran. We show that mislocations of the order of 10-20 km affecting the epicenters, as well as larger mislocations in hypocentral depths, calculated from a global seismic network can be effectively removed by applying source-specific station corrections applied to the standard IASPEI91 travel times. This method is valid only for the area where calibration events are located but it is valid for any subset of the station network used for the calibration.329 197 - PublicationOpen AccessStudy of recent seismicity in the area of Southern Apennines(2007-06-26)
; ; ; ; ; ;Maggi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Cimini, G. B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Console, R. ;Frepoli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; ; ; ;In questo lavoro è stata effettuata una dettagliata analisi della sismicità dell’Italia meridionale in particolare della zona comprendente l’Appennino lucano e l’avanfossa bradanica. Sono stati utilizzati i tempi d’arrivo delle fasi P e S di terremoti locali registrati dalla Rete Sismica Nazionale (RSNC), dalla rete temporanea SAPTEX (2001-2004) (Cimini et al., 2006), e dalla rete locale dell’Eni-Agip operante nella Val d’Agri, registrate nel periodo 2001-2006. In questo modo è stato creato un database costituito da 7570 fasi P e 4956 fasi S, associate a 514 eventi con magnitudo maggiore di 2.0. Lo studio realizzato consiste nel: 1) Calcolo del rapporto VP/VS utilizzando il metodo di Wadati modificato (Chatelain, 1978), ottenendo un valore di 1.83 (Fig.1) leggermente superiore a quello ottenuto da studi precedenti; 2) Analisi del profilo di velocità 1D che meglio approssima la struttura crostale dell’area studiata (Fig.2) utilizzando il codice VELEST (Kissling et al., 1995) e tre modelli iniziali ottenuti da studi precedenti (Chiarabba and Frepoli, 1997; Cassinis et al., 2003; Chiarabba at al., 2005; Frepoli et al., 2005). 3) Localizzazione ipocentrale, calcolo dei meccanismi focali e campo di stress. Le localizzazioni ipocentrali calcolate sono prevalentemente di qualità A(243) e B(59), così come definite dal programma HYPOELLIPSE (Lahr, 1989). Rispetto a quelle ottenute utilizzando i dati della sola rete RSNC, esse risultano avere profondità ipocentrali piú vincolate ed errori di localizzazione inferiori. Considerando la distribuzione della sismicità in Fig.3 si possono distinguere tre zone principali: una situata nella parte ovest della catena appenninica, caratterizzata soprattutto da eventi piú superficiali; una situata in corrispondenza dell’avanfossa bradanica caratterizzata da una sismicità sparsa e da eventi piú profondi; ed infine un gruppo di eventi sparsi localizzati nell’area della Sila, separati da quelli esistenti nella zona del monte Pollino da un evidente gap sismico. Seguendo la procedura di calcolo dei meccanismi focali, col metodo delle polarità dei primi arrivi, ne sono stati selezionati 69 in base ai due fattori di qualità definiti dal codice FPFIT (Reasenberg and Oppenheimer, 1985). Le soluzioni ottenute sono in gran parte normali e trascorrenti con gli assi T che descrivono una generalizzata estensione dell’Appennino lucano in direzione NE-SW. Per la determinazione del campo di stress regionale è stata utilizzata la tecnica di inversione elaborata da Gephart & Forsyth (1984). I risultati ottenuti sono coerenti con i precedenti studi nella stessa area.191 392 - PublicationOpen AccessBåth's law and the self-similarity of earthquakes(2003)
; ; ; ; ; ; ; We revisit the issue of the so-called Bath’s law concerning the difference D1 between the magnitude of the main shock and the second largest shock in the same sequence. A mathematical formulation of the problem is developed with the only assumption being that all the events belong to the same self-similar set of earthquakes following the Gutenberg– Richter magnitude distribution. This model shows a substantial dependence of D1 on the magnitude thresholds chosen for the main shocks and the aftershocks and in this way partly explains the large D1 values reported in the past. Analysis of the New Zealand and Preliminary Determination of Epicenters (PDE) catalogs of shallow earthquakes demonstrates a rough agreement between the average D1 values predicted by the theoretical model and those observed. Limiting our attention to the average D1 values, Ba ̊th’s law does not seem to strongly contradict the Gutenberg–Richter law. Nevertheless, a detailed analysis of the D1 distribution shows that the Gutenberg–Richter hypothesis with a constant b-value does not fully explain the experimental observations. The theoretical distribution has a larger proportion of low D1 values and a smaller proportion of high D1 values than the experimental observations. Thus, Ba ̊th’s law and the Gutenberg–Richter law cannot be completely reconciled, although based on this analysis the mismatch is not as great as has sometimes been supposed.116 51