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Maggi, C.
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Maggi, C.
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- 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 - PublicationRestrictedSeismotectonic of Southern Apennines from recent passive seismic experiments(2011-03)
; ; ; ; ; ;Frepoli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Maggi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Cimini, G. B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Marchetti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ; ; We used data of local earthquakes collected during two recent passive seismic experiments carried out in southern Italy in order to study the seismotectonic setting of the Lucanian Apennine and the surrounding areas. Based on continuous recordings of the temporary stations we extracted over 15,600 waveforms, which were hand-picked along with those recorded by the permanent stations of the Italian national seismic network obtaining a dense, high-quality dataset of P- and S-arrival times. We examined the seismicity occurring in the period 2001–2008 by relocating 566 out of 1047 recorded events with magnitudes ML ≥1.5 and computing 162 fault-plane solutions. Earthquakes were relocated using a minimum one-dimensional velocity model previously obtained for the region and a Vp/Vs ratio of 1.83. Background seismicity is concentrated within the upper crust (between 5 and 20km of depth) and it is mostly clustered along the Lucanian Apennine chain axis. A significant feature extracted from this study relates to the two E–W trending clusters located in the Potentino and in the Abriola–Pietrapertosa sector (central Lucania region). Hypocentral depths in both clusters are slightly deeper than those observed beneath the Lucanian Apennine. We suggest that these two seismic features are representative of the transition from the inner portion of the chain to the external margin characterized by dextral strike-slip kinematics. In the easternmost part of the study area, below the Bradano foredeep and the Apulia foreland, seismicity is generally deeper and more scattered. The sparse seismicity localized in the Sibari Plain, in the offshore area along the northeastern Calabrian coast and in the Taranto Gulf is also investigated thanks to the new recordings. This seismicity shows hypocenters between 12 and 20km of depth below the Sibari Plain and is deeper (foci between 10 and 35km of depth) in the offshore area of the Taranto Gulf. 102 well-constrained fault-plane solutions, showing predominantly normal and strike-slip character with tensional axes (T-axes) generally NE oriented, were selected for the stress tensor analysis. We investigated stress field orientation inverting focal mechanism belonging to the Lucanian Apennine and the Pollino Range, both areas characterized by a more concentrated background seismicity.255 44 - PublicationOpen AccessRECENT SEISMICITY (2000-2007) IN THE TIBURTINI-PRENESTINI MOUNTAINS REGION (LATIUM, ITALY)(2007-09-14)
; ; ; ; ; ; ;Frepoli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Pagliuca, N. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Maggi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Marchetti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Marra, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Pirro, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; ; ; ; ; ; ; ; ;Boncio, P.; Universita’ degli Studi “G. D’annunzio” Chieti ;Caputo, R.; University of Basilicata; A detailed knowledge of the seismicity distribution enables us to gain a better understanding of the recent tectonic evolution and the present-day state of stress of the Tiburtini and Prenestini Mountains region, whose seismic importance is related with the nearness to the town of Rome. It has been carried out an analysis of the seismicity of the region using the data recorded by the permanent stations belonging to the Italian National Seismic Network (RSNC) from 2000, and subsequently integrated with data of local seismic network from 2003 to 2007. The increase of the number of stations in the last years allow us to obtain better quality earthquake localization as before done. We have produced a large database of re-picked events collecting arrival times of P and S waves of local earthquakes with magnitude larger than 2.0, belonging to the 2000-2007 period. The work is subdivided into three step. The first one consists in the determination of the VP/VS ratio using the modified Wadati method. In the second step we perform the analysis of the 1D velocity model that better approximates the structure of the crust in the studied area using the VELEST code (Kissling et al., 1995). Finally, we have the step with earthquake locations and focal mechanisms computation using the first motion polarities method. Fault plane solutions are selected following the two quality factors defined by the FPFIT code (Reasenberg and Oppenheimer, 1985). For the determination of the regional stress field it is used the focal mechanism inversion method elaborated by Gephart and Forsyth (1984). These results are compared with those available from the historical seismicity that struck the region under study.139 137 - PublicationRestrictedRecent seismicity and crustal stress field in the Lucanian Apennines and surrounding areas (Southern Italy): Seismotectonic implications(2009-01-01)
; ; ; ; ; ;Maggi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Frepoli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Cimini, G. B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Console, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ; ; We analyzed the instrumental seismicity of Southern Italy in the area including the Lucanian Apennines and Bradano foredeep, making use of the most recent seismological data base available so far. P- and S-wave arrival times, recorded by the Italian National Seismic Network (RSNC) operated by the Istituto Nazionale di Geofisica e Vulcanologia (INGV), were re-picked along with those of the SAPTEX temporary array deployed in the region in the period 2001–2004. For some events located in the upper Val d'Agri, we also used data from the Eni-Agip oil company seismic network. We examined the seismicity occurred during the period between 2001 and 2006, considering 514 events with magnitudes M≥2.0. We computed the VP/VS ratio obtaining a value of 1.83 and we carried out an analysis for the one-dimensional (1D) velocity model that approximates the seismic structure of the study area. Earthquakes were relocated and, for well- recorded events, we also computed 108 fault plane solutions. Finally, using 58 solutions, the most constrained, we computed regional stress field in the study area. Earthquake distribution shows three main seismic regions: the westernmost (Lucanian Apennines) characterized by high background seismicity, mostly with shallow hypocenters, the easternmost below the Bradano foredeep and the Murge with deeper and more scattered seismicity, and finally the more isolated and sparse seismicity localized in the Sila Range and in the offshore area along the northeastern Calabrian coast. Focal mechanisms computed in this work are in large part normal and strike-slip solutions and their tensional axes (T-axes) have a generalized NE–SW orientation. The denser station coverage allowed us to improve hypocenters determination compared to those obtained by using only RSNC data, for a better characterization of the crustal and subcrustal seismicity in the study area.234 41 - PublicationRestrictedSeismicity, seismogenic structures, and crustal stress fields in the greater Rome area (central Italy)(2010-12-02)
; ; ; ; ; ; ; ;Frepoli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Marra, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Maggi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Marchetti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Nardi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Pagliuca, N. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Pirro, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; ; ; ; ; ; Instrumental seismicity of the greater Rome area is analyzed using the most recent seismological database. The aim of this study is to identify potential seismogenic structures responsible for the moderate seismicity that characterizes this sector, where no surface faulting is expected on the basis of the absence of strong local earthquakes, as evidenced by the 2000‐year‐long historical record. Nevertheless, in light of the great value and the high vulnerability of the architectural and monumental patrimony of Rome, even the occurrence of moderate events imposes a careful assessment of the hazard, linked to the presence of active faults that are undetectable by means of classic geological field investigation. Seismic data here analyzed belong to the period 1997–2008 and show local magnitude (ML) ranging from 1.5 to 4.7. To better constrain the hypocentral depths, we computed the Vp/Vs ratio using a modified Wadati method and the minimum 1‐D velocity model that approximates the seismic structure of the study area. Moreover, we applied a double difference hypocentral determination technique to improve earthquake locations. Most of the located seismicity appears to be concentrated within seven main clusters. Spatial distribution of the seismicity allowed us to identify several seismogenic structures, corresponding to previously undetected or only supposed active faults. The stress tensor obtained by inverting the focal mechanisms computed in this study is in agreement with the NE–SW extensional tectonic stress active in the inner chain of the Apennines, although there is evidence of some local stress field heterogeneities.264 45 - 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 AccessModello di velocità 1D e distribuzione della microsismicità nell’area dei Monti Tiburtini-Prenestini e Simbruini (Appennino centrale).(2007-11-13)
; ; ; ; ; ; ;Frepoli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Pagliuca, N. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Maggi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Marchetti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Marra, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Pirro, M.; ; ; ; ; ;; EVA, C.We analyzed the seismicity of the Tiburtini, Prenestini and Simbruini Mountains region, whose seismic importance is related with the nearness to the town of Rome. It has been carried out an analysis of the seismicity of the region using the data recorded by the permanent stations belonging to the Italian National Seismic Network (RSNC) from 2000, and subsequently integrated with data of local seismic network from 2003 to 2007. The increase of the number of stations in the last years allow us to obtain better quality earthquake localization as before done. We have produced a large database of re-picked events collecting arrival times of P and S waves of local earthquakes with magnitude larger than 2.0, belonging to the 2000-2007 period. We computed an average Vp/Vs ratio using a modified Wadati method (Chatelain, 1978) obtaining a value of 1.85. To better constrain the hypocentral depths we performed an analysis to find the best P-wave one-dimensional (1D) velocity model for the crustal seismic structure of the study area, using the VELEST algorithm (Kissling et al., 1995).161 181