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Castro, Raúl R
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Castro, Raúl R
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- PublicationOpen AccessA review of nonparametric attenuation functions computed for different regions of Italy(1999-08)
; ; ; ; ; ;Castro, R. R.; División Ciencias de la Tierra, CICESE, Baja California, México ;Mucciarelli, M.; Università della Basilicata, Potenza, Italy ;Monachesi, G.; Osservatorio Geofisico Sperimentale di Macerata, Italy ;Pacor, F.; ISMES, Divisione Geofisica, Bergamo, Italy ;Berardi, R.; Ente Nazionale per l'Energia Elettrica (ENEL), Roma, Italy; ; ; ; We used a set of previously published nonparametric attenuation functions to calculate average functions for the Italian region. These nonparametric functions describe the spectral amplitude decay of the S waves as a function of distance for 14 frequencies between 1 and 20 Hz for the regions of Lombardia-Piemonte, Eastern Sicily, Friuli, Marche and the Central Apennines. Since all the attenuation functions were obtained using the same methodology, we were able to make a fair comparison of the attenuation characteristics of the different regions. In general, while the Central Apennines show the strongest amplitude decay for all the frequencies analyzed, the regions of Lombardia and Eastern Sicily show the smallest attenuation. The Marche region also shows a strong amplitude decay, particularly for frequencies f > 3 Hz, and in the frequency band between 1 and 3 Hz the rate of decay of the spectral amplitudes with distance becomes similar to that of the region of Friuli. Since the attenuation functions analyzed represent different geologic and tectonic environments, we used them to calculate an average set of attenuation functions, one per frequency, for the hypocentral distance range between 10 and 120 km. The resulting functions permit a mean attenuation correction to spectral records of S waves in regions of Italy where the specific values of the attenuation parameters are unknown.158 227 - PublicationOpen AccessOverview on the strong motion data recorded during the May-June 2012 Emilia seismic sequence(2013)
; ; ; ; ; ; ; ; ; ; ;Luzi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Pacor, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Ameri, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Puglia, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Burrato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Massa, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Augliera, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Franceschina, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Lovati, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Castro, R.; Departamento de Sismología, División Ciencias de la Tierra, centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Ensenada, Baja California, 22860, México.; ; ; ; ; ; ; ; ; On 20 May 2012, at 02:03:52 GMT, an earthquake with Mw 6.1 (RCMT, http://www.bo.ingv.it/RCMT) occurred in northern Italy striking a densely populated area. The mainshock was followed a few hours later by two severe aftershocks having the same local magnitude (Ml 5.1, 1 and 2 in Figure 1a), and by hundreds of smaller aftershocks. Nine days later, on 29 May, at 07:00:03 GMT, a second event with moment magnitude Mw 6.0 (RCMT, http://www.bo.ingv.it/RCMT) occurred to the west, on an adjacent fault segment. This event was also followed by hundreds of aftershocks, three of them having local magnitude 5.3, 5.2 and 5.1 (3, 4 and 5, respectively, in Figure 1a) (locations from Istituto Nazionale di Geofisica e Vulcanologia, hereinafter INGV, http://iside.rm.ingv.it/; Malagnini et al., 2012; Scognamiglio et al., 2012). Despite the moderate number of casualties if compared to other major events in the Italian history, the economic loss was extremely high, resulting in about EUR 5 billion (AON Benfield, 2012, http://www.aon.com/), as the majority of Italian industrial activities and infrastructures concentrate in this area, the eastern Po plain, which is the largest sedimentary basin in Italy. The mainshocks are associated to two thrust faults with an approximate E-W trend dipping to the South (Figure 1b). The majority of the faults in this region are located in the upper crust, at depths lower than 10 km. The two main shocks are among the strongest earthquakes generated by thrust faults ever recorded in Italy in the instrumental era. The Emilia sequence has been extensively recorded by several strong-motion networks, operating in the Italian territory and neighbouring countries. Some of the networks acquire continuous data streams at their national data centres, which are nodes of EIDA (European Integrated Data Archive, hhtp://eida.rm.ingv.it), a federation of several archives, so that the waveforms can be obtained immediately after the occurrence of an event. Other networks, such as the Italian accelerometric network (RAN), managed by the Italian Department of the Civil Protection (hereinafter DPC), distribute the acceleration waveforms through their web site (http://protezionecivile.gov.it). The data set explored in this study is relative to the six events of the sequence having Ml > 5 (Table 1) and consists in 365 accelerograms recorded within a distance of 200 km from the epicentres, that were provided by the permanent and temporary seismic networks of INGV, the Swiss Seismological Service (SED, http://www.seismo.ethz.ch/index) and the DPC.829 696 - PublicationRestrictedStochastic strong-motion simulation of the Umbria-Marche earthquake of September 1997 (Mw 6): comparison of different approaches(2008)
; ; ; ; ; ; ;Castro, R. R.; Cicese ;Pacor, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Franceschina, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Bindi, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Zonno, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Luzi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia; ; ; ; ; Abstract We simulated strong-motion records from the Umbria–Marche, central Italy, earthquake (Mw 6) of September 1997 using a frequency-dependent S-wave radiation function. We compared the observed acceleration spectra, from strongmotion instruments located in the near field and at regional distances, with those simulated using the stochastic modeling technique of Beresnev and Atkinson (1997, 1998), and modified to account for a frequency-dependent radiation pattern correction. By using the frequency-dependent radiation function previously obtained by Castro et al. (2006), we reduced the overall fitting error of the acceleration spectra by about 9%. In general, we observed that the frequency-dependent radiation pattern correction has a small effect on the spectral amplitudes compared with site effects, which is an important factor controlling the strong-motion records generated by the 1997 Umbria–Marche earthquake. In addition, we modeled the observed ground-motion records using the dynamic corner frequency model of Motazedian and Atkinson (2005) to reproduce the directivity effects, reducing the average error of the spectral amplitudes by 24%. We concluded that although the frequencydependent radiation pattern correction affects the frequency content of the spectral amplitudes simulated, site and directivity effects are more relevant.158 31 - PublicationOpen AccessTask 4 - Garda - Deliverable D13: Scenari di scuotimento al bedrock a vari livelli di complessità(2007-07)
; ; ; ; ; ; ; ; ; ; ; ;Pessina, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Franceschina, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Augliera, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Massa, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Di Giacomo, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Marzorati, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;D'Alema, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Lovati, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Pacor, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Castro, R. R.; CICESE Messico ;Vannoli, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; ; ; ; ; ; ; 179 345 - PublicationOpen AccessDepth-Dependent Shear-Wave Attenuation in Central Apennines, ItalyWe used 1029 earthquakes, with magnitudes ranging from M 3.0 to M 6.5, located in central Apennines, Italy, and recorded by 414 local stations to study the variation of the quality factor QS of shear waves with depth. We first determined average nonparametric attenuation functions in the frequency band from 0.5 to 20 Hz and hypocenter distances less than 155 km to correct the observed acceleration spectra for attenuation effects. Then, we separated source and site effects from the corrected spectral records to determine the changes of QS with depth. We used a 1D local shear-wave velocity model to calculate the travel times of the source-station paths, and we inverted the observed spectra to determine QS in three different depth intervals (0–4 km, 4–10 km and 10–15 km) and five frequencies (0.5, 1, 4, 10 and 20 Hz). We found that QS increases with frequency at all depths considered and tends to have lower values at shallow depths. The average value of QS is consistent with previous studies made in central Italy and can be approximated by QS = 43f0.94. To describe the frequency dependence of QS with depth (H), we determine the following relations: QS = 5.5f1.39, 0.5 ≤ f ≤ 10 Hz and QS = 151.5, f > 10 Hz for 0–4 km, QS = 52f0.87 for 4 < H < 10 km and QS = 51f0.92 for 10 ≤ H ≤ 15 km. We conclude that the Q-depth-dependent model can be useful to improve estimates of source parameters and ground motion prediction in the central Apennines region of Italy.
112 42 - PublicationRestrictedGround motion predictions from empirical attenuation relationships versus recorded data: the case of the 1997-98 Umbria-Marche (Central Italy) strong motion data-set(2006)
; ; ; ; ; ;Bindi, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Luzi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Pacor, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Franceschina, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Castro, R. R.; Centro de Investigacio´n Cientı´fica y de Educacio´n Superior de Ensenada (CICESE); ; ; ; We evaluate the goodness of fit of attenuation relations commonly used for the Italian national territory (Sabetta and Pugliese, 1996) by using the maximum likelihood approaches of Spudich et al. (1999) and Scherbaum et al. (2004). According to the classification scheme proposed by Scherbaum et al. (2004), the Sabetta and Pugliese (1996) relationships show consistent discrepancies between the predicted and the observed peak ground acceleration (PGA) at rock sites in the Umbria- Marche region, central Italy; however, at soft sites the agreement between observations and prediction is satisfactory. The bias of the residuals, computed with the Sabetta and Pugliese (1996) models for PGA, peak ground velocity, (PGV) and pseudovelocity response spectrum (PSV) (for Ml 4–6 and epicentral distances up to 100 km) is negative. This means that on the average, the predictions overestimate the observations, but the overestimation decreases with increasing magnitude. Then, we present regional predictive relations (UMA05) for maximum horizontal PGA, PGV, and 5%-damped PSV, derived from the strong-motion data recorded in the Umbria-Marche area and classified as to four site categories. The UMA05 attenuation relationships for rock sites are log10 (PGA) 2.487 0.534Ml 1.280 log10 (R2 3.942)0.5 0.268 log10 (PGV) 1.803 0.687Ml 1.150 log10 (R2 2.742)0.5 0.300 and log10 (PGA) 2.500 0.544Ml 1.284 log10 Rh 0.292 log10 (PGV) 1.752 0.685Ml 1.167 log10 Rh 0.297, where PGA is measured in fraction of g and PGV in centimeters per second, Ml is the local magnitude in the range 4–6, R is the epicentral distance in the range 1–100 km, and Rh is the hypocentral distance in kilometers. We used the random effect model (Brillinger and Priesler, 1985; Abrahamson and Youngs, 1992; Joyner and Boore, 1993; Joyner and Boore, 1994) to estimate the component of variance related to the earthquake-to-earthquake, station-to-station, and record-to-record variability, and to quantify the benefit of introducing a site classification in the attenuation model to reduce the variance. The introduction of the site classification in the attenuation model allows a reduction of the station-to-station component of variability (from 0.19 to 0.14 for PGA, and from 0.21 to 0.18 for PGV). We also found that the recordto- record component represents the largest contribution to the model uncertainty.187 27 - PublicationRestrictedNear-Source Attenuation and Spatial Variability of the Spectral Decay Parameter Kappa in Central Italy(2022)
; ; ; ; ; ; ;; ;; ; We study the spectral decay parameter κ using S-wave recordings from the central Italy dense regional array. The data set used consists of 266 earthquakes, 353 stations, and 13,952 observations of κ with a mean value of 0.0412 ± 0.0177 within the distance range of 7.1–168.8 km. We model the variation of κ with hypocenter distance r as κ r κ0 κs ̃κ r , in which κ0 and κs represent the near-site and the near-source decay parameters, respectively, and ̃κ r the average κ along the S-wave source-station paths. We first determine ̃κ r with a nonparametric inversion approach and then we solved for κ0 and κs with a second inversion. We found that ̃κ r increases with distance within the whole distance range analyzed (9.2–80.6 km). The near-source decay parameter takes values in the range 0:0 < κs ≤ 0:026 with a mean value of 0.003 ± 0.006, which represents 7.52% of the mean value of the observed κ. The values of the near-site decay parameter vary in the range 0:0035 ≤ κ0 ≤ 0:0823 with a mean value of 0.0298 ± 0.0133, that is, 72.28% of the mean value of the κ observed. We conclude that most of the high- frequency attenuation takes place near the site, because ̃κ r contributes with only 20.2% of the spectral decay. We also investigate the spatial variability of κ by determining ̃κ r within four quadrants that divide the studied region taking as a reference axis the Apennines chain orientation. We found higher values of ̃κ r in the southern quad- rants, where seismicity and faulting are more active, and less attenuation in the more stable northeast quadrant.258 67 - PublicationOpen AccessBody-wave Attenuation in the Region of Garda, Italy(2008-07)
; ; ; ; ;Castro, R.; Cicese, Mexico ;Massa, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Augliera, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Pacor, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia; ; ; We analyzed the spectral amplitude decay with hypocentral distance of P and S waves generated by 76 small magnitude earthquakes (ML 0.9-3.8) located in the Garda region, Central-Eastern Alps, Italy. These events were recorded by 18 stations with velocity sensors, in a distance range between 8 and 120 km. We calculated nonparametric attenuation functions (NAF) and estimated the quality factor Q of both body waves at 17 different frequencies between 2 and 25 Hz. Assuming a homogeneous model we found that the Q frequency dependence of P and S can be approximated with the functions QP=65 f 0.9 and QS=160 f 0.6, respectively. At 2 Hz the QS / QP ratio reaches the highest value of 2.8. At higher frequencies QS/QP varies between 0.7 and 1.7, suggesting that for that frequency band scattering may be an important attenuation mechanism in the region of Garda. To explore the variation of Q with depth, we estimated Q at short (r ≤ 30 km) and intermediate (35-90 km) distance paths. We found that in the shallow crust P waves attenuate more than S (1.3 < QS / QP < 2.5). Moreover, P waves traveling along paths in the lower crust (depths approximately greater than 30 km) attenuate more than S-waves. To quantify the observed variability of Q with depth we considered a 3-layer model and inverted the NAF to estimate Q in each layer. We found that in the crust Q increases with depth. However, in the upper mantle (~40-50 km depth) Q decreases and in particular the high frequency QS (f>9 Hz) has values similar to those estimated for the shallow layer of the crust.214 634 - PublicationOpen AccessAn attenuation study in Southern Italy using local and regional earthquakes recorded by seismic network of Basilicata(2004)
; ; ; ;Castro, R. R.; CICESE, División Ciencias de la Tierra, Departamento de Sismología, Ensenada, Baja California, México ;Gallipoli, M. R.; Istituto di Metodologie per l Analisi Ambientale (IMAA) CNR, Tito Scalo (PZ), Italy ;Mucciarelli, M.; Di.S.G.G., Università degli Studi della Basilicata, Potenza, Italy; ; We determined a set of empirical functions that describe the spectral amplitude decay of S-waves with distance in Southern Italy. We analyzed 32 earthquakes with magnitudes ML 2.0-5.4 and hypocentral distances ranging between 12 and 216 km. We obtained attenuation functions for 14 frequencies(1.0< f<20.0 Hz). We compared these functions with average non-parametric attenuation functions reported by Castro et al. (1999) for different regions of Italy, and we observe that at low frequencies (f<5.0 Hz) the spectral amplitudes from earthquakes in Southern Italy decay faster than the average. However, at high frequencies ( f > 5.0 Hz), the spectral amplitudes are above the average. At higher frequencies ( f > 10 Hz), the attenuation functions obtained for Southern Italy are slightly above the standard deviation of the average attenuation functions. It is possible that in this frequency range (10-20 Hz) site effects may influence the amplitude decay. In order to quantify the attenuation of the S-waves, we estimated the quality factor Q modeling the empirical attenuation functions using the following parametric form: A( f , r)=10/r b·e- pfR/Q ß; where 1.6 = f = 10.0 Hz is the frequency band with minimum effect of instrument and site response, r = 120 km is the distance range where the rate of decay of the spectral amplitudes is approximately constant, R=(r-10) and ß=3.2 km/s. We found that the exponent b=1.0±0.2 in the frequency band analyzed and Q shows a frequency dependence that can be approximated by the function Q=32.1 f 1.7.246 194 - PublicationOpen AccessTemporal Variation of the Spectral Decay Parameter Kappa Detected before and after the 2016 Main Earthquakes of Central Italy(2022)
; ; ; ; ; ; ; ; ; ; ; ; ; We investigated the temporal variation of the spectral decay parameter κ before and after two main earthquakes that occurred in the central Italy region, namely the Amatrice (Mw 6.0) of 24 August 2016 and the Norcia (Mw 6.5) of 30 October 2016 earthquakes. For this analysis, we used seismograms from the central Italy dense seismic array stations, and earthquakes located at hypocenter distances r < 80 km, having magnitudes Mw 3.4–6.5. The dataset consists of 393 events recorded at 92 stations. We estimated, for both earthquake sequences, average functions κ˜(r) that describe the distance dependence of κ along the S-wave source-station paths using acceleration spectra from foreshocks, mainshock, and aftershocks. We observed that there was a regional attenuation drop within approximately two months after the Amatrice earthquake. Then, κ˜(r) tends to return toward the attenuation values observed before the occurrence of the main event, namely to the values of κ˜(r) obtained from the foreshocks, when the earthquake cycle is probably completed. We also estimated the near-source kappa (κs) using aftershocks from 24 August 2016 to 3 September 2016. The results show that the values of κs are lower than those from aftershocks located to the north near the epicenter of the Amatrice earthquake, suggesting that the tectonic stress was probably high near the rupture zone, and that there may be a likely fluid flow of crustal fluids. κ˜(r) obtained from the foreshocks of the Norcia earthquake is like that calculated with the records of the Amatrice aftershocks. Then, κ˜(r) drops to lower attenuation values during the Norcia main event and tends to increase again during the aftershocks. From the analysis of these two earthquake sequences that occurred in a short-time interval in central Italy, we conclude that the temporal variation of κ˜(r) could be a valuable indicator to monitor the earthquake cycle.301 18