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de Lorenzo, Salvatore
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de Lorenzo, Salvatore
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- PublicationOpen AccessSeismicity of the Gargano promontory (Southern Italy) after 7 years of local seismic network operation: Data release of waveforms from 2013 to 2018(2021-04)
; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ;; ; ; ;; The University of Bari (Italy), in cooperation with the National Institute of Geophysics and Volcanology (INGV) (Italy), has installed the OTRIONS micro-earthquake network to better understand the active tectonics of the Gargano promontory (Southern Italy). The OTRIONS network operates since 2013 and consists of 12 short period, 3 components, seismic stations located in the Apulian territory (Southern Italy). This data article releases the waveform database collected from 2013 to 2018 and describes the characteristics of the local network in the current configuration. At the end of 2018, we implemented a cloud infrastructure to make more robust the acquisition and storage system of the network through a collaboration with the RECAS-Bari computing centre of the University of Bari (Italy) and of the National Institute of Nuclear Physics (Italy). Thanks to this implementation, waveforms recorded after the beginning of 2019 and the station metadata are accessible through the European Integrated Data Archive (EIDA, https://www.orfeus-eu.org/data/eida/nodes/INGV/).295 32 - PublicationOpen AccessSeismogenic Structure Orientation and Stress Field of the Gargano Promontory (Southern Italy) From Microseismicity Analysis(2021-04)
; ; ; ; ; ; ; ; ; ; ; Historical seismic catalogs report that the Gargano Promontory (southern Italy) was affected in the past by earthquakes with medium to high estimated magnitude. From the instrumental seismicity, it can be identified that the most energetic Apulian sequence occurred in 1995 with a main shock of MW = 5.2 followed by about 200 aftershocks with a maximum magnitude of 3.7. The most energetic earthquakes of the past are attributed to right-lateral strike-slip faults, while there is evidence that the present-day seismicity occur on thrust or thrust-strike faults. In this article, we show a detailed study on focal mechanisms and stress field obtained by micro-seismicity recorded from April 2013 until the present time in the Gargano Promontory and surrounding regions. Seismic waveforms are collected from the OTRIONS Seismic Network (OSN), from the Italian National Seismic Network (RSN), and integrated with data from the Italian National Accelerometric Network (RAN) in order to provide a robust dataset of earthquake localizations and focal mechanisms. The effect of uncertainties of the velocity model on fault plane solutions (FPS) has been also evaluated indicating the robustness of the results. The computed stress field indicates a deep compressive faulting with maximum horizontal compressive stress, SHmax, trending NW-SE. The seismicity pattern analysis indicates that the whole crust is seismically involved up to a depth of 40 km and indicates the presence of a low-angle seismogenic surface trending SW-NE and dipping SE-NW, similar to the Gargano–Dubrovnik lineament. Shallower events, along the eastern sector of the Mattinata Fault (MF), are W-E dextral strike-slip fault. Therefore, we hypothesized that the seismicity is locally facilitated by preexisting multidirectional fractures, confirmed by the heterogeneity of focal mechanisms, and explained by the different reactivation processes in opposite directions over the time, involving the Mattinata shear zone.59 63 - PublicationOpen AccessIs the dependence on the temperature of the friction important in stress triggering phenomena? The case of the 2000 Iceland seismic sequence(2012-04)
; ; ; ; ;Bizzarri, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Crupi, P.; Università degli Studi di Bari ;de Lorenzo, S.; Università degli Studi di Bari ;Loddo, M.; Università degli Studi di Bari; ; ; We perform numerical experiments by using a mass–spring fault model subject to an external coseismic stress perturbation due to a remote seismic event happening on another fault, the causative fault. In particular, the aim of this study is to investigate the instantaneous fault interaction and possible triggering that happens when a fault perturbed by a stress change fails before the so–called unperturbed instability. As a realistic example we focus our attention on the instantaneous dynamic triggering phenomena occurred during the 17 June 2000 south Iceland seismic sequence in the South Iceland Seismic Zone (SISZ, Reykjanes Peninsula). The main event (Ms 6.6) was followed by three large events within a few tens of seconds (8, 26 and 30 s, respectively) located in a neighborhood of several tens of km. Among them the 26 s event was the best constrained (Bizzarri and Belardinelli, 2008). In the present study, conditions to simulate the instantaneous dynamic triggering connected to the former three events, have been investigated using the simple 1–D spring–slider analogue model representing a fault governed by the rate– and state–dependent friction laws. In previous studies suitable constitutive parameters of the modeled fault which allow the instantaneous triggering of the three events, have been found (Antonioli et al., 2006) and, furthermore, it was also shown how the dynamics of the 26 s event strongly depends on the assumed constitutive law and stress conditions (Bizzarri and Belardinelli, 2008) by considering the Dieterich–Ruina (DR henceforth) and the Ruina–Dieterich (RD henceforth) governing laws. In this context take place the present study original contribution that is to better understand if the conditions of instantaneous dynamic triggering (focusing on the case of the 26 s triggered event) provide any significant differences if modeled with a different rate– and state–dependent governing equation, the Chester and Higgs law (CH henceforth; see Chester and Higgs, 1992; Bizzarri, 2010b; Bizzarri, 2010c) which accounts for the thermal effect for frictional heating which may occur during seismic sliding.125 98 - PublicationOpen Access3D-Kernel Based Imaging of an Improved Estimation of (Qc) in the Northern Apulia (Southern Italy)(2021)
; ; ; ; ; ; ; ; ; ; ; We investigate crustal seismic attenuation by the coda quality parameter (Qc) in the Gargano area (Southern Italy), using a recently released dataset composed of 191 small earthquakes (1.0 ≤ ML ≤ 2.8) recorded by the local OTRIONS and the Italian INGV seismic networks, over three years of seismic monitoring. Following the single back-scattering theoretical assumption, Qc was computed using different frequencies (in the range of 2–16 Hz) and different lapse times (from 10 to 40 s). The trend of Qc vs. frequency is the same as that observed in the adjacent Umbria-Marche region. Qc at 1 Hz varies between 11 and 63, indicating that the area is characterized by active tectonics, despite the absence of high-magnitude earthquakes in recent decades. The 3D mapping procedure, based on sensitivity kernels, revealed that the Gargano Promontory is characterized by very low and homogeneous Qc at low frequencies, and by high and heterogeneous Qc at high frequencies. The lateral variations of Qc at 12 Hz follow the trend of the Moho in this region and are in good agreement with other geophysical observations.49 36 - PublicationOpen AccessQβ, Qc, Qi, Qs of the Gargano Promontory (Southern Italy)(2023-08)
; ; ; ; ; ; ; ;; ;; ; ;We have provided the first estimate of scat- tering and intrinsic attenuation for the Gargano Prom- ontory (Southern Italy) analyzing 190 local earthquakes with M L ranging from 1.0 to 2.8. To separate the intrin- sic Q i and scattering Q s quality factors with the Wen- nerberg approach (1993), we have measured the direct S waves and coda quality factors ( Q 𝛽 , Q c ) in the same volume of crust. Q 𝛽 parameter is derived with the coda normalization method (Aki 1980) and Q c factor is derived with the coda envelope decay method (Sato 1977). We selected the coda envelope by performing an automatic picking procedure from T start = 1.5T S up to 30 s after origin time (lapse time T L ). All the obtained quality factors clearly increase with frequency. The Q c values correspond to those recently obtained for the area. The estimated Q i are comparable to the Q c at all frequencies and range between 100 and 1000. The Q s parameter shows higher values than Q i , except for 8 Hz, where the two estimates are closer. This implies a pre- dominance of intrinsic attenuation over the scattering attenuation. Furthermore, the similarity between Q i and Q c allows us to interpret the high Q c anomaly previ- ously found in the northern Gargano Promontory up to a depth of 24 km, as a volume of crust characterized by very low seismic dumping produced by conversion of seismic energy into heat. Moreover, most of the earth- quake foci fall in high Q i areas, indicating lower level of anelastic dumping and a brittle behavior of rocks.39 10 - PublicationRestricted2D kernel-based imaging of coda-Q space variations in the Gargano Promontory (Southern Italy)(2019)
; ; ; ; ; ; ; Crustal seismic attenuation in the Gargano Promontory (Southern Italy) was inferred by analyzing coda waves of about one hundred small magnitude earthquakes recorded by the OTRIONS local seismic network. Coda attenuation Qc was computed using the Sato (1977) model, i.e. the assumption of single back-scattering, at different lapse times and at different frequencies. Average Qc is comparable with the same quantity measured in the adjacent area of the Umbria–Marche region (central Italy). A recent kernel-based imaging technique for Qc was then applied and the results evidence a well confined zone located South West of the investigated area, showing a sharp Qc anomaly. While Qc cannot be directly related to the physical properties of the propagation medium, its spatially-dependent modeling allows an interpretation in the light of other geophysical and geological information. Our results were then interpreted following the two extreme hypotheses according to which Qc could be representative of the effect of only intrinsic attenuation or of only scattering from the heterogeneities. Both the hypothesis correlate with the observation of anomalies in several geophysical parameters, such as heat flow, magnetic field, gravity, density, seismic velocity in the southwestern Gargano. Moreover, the Qc images support the results obtained in a recent study that shows clear variations in the rheological properties of the Gargano. The results obtained at local scale confirm and detail previous regional scale studies on attenuation and highlight for the first time the presence of a positive Qc anomaly in the south-western part of the Gargano Promontory.89 2 - PublicationRestrictedFault plane orientations of microearthquakes at Mt. Etna from theinversion of P-wave rise times(2010)
; ; ; ; ; ;de lorenzo, S.; Dipartimento di Geologia e Geofisica & Centro Interdipartimentale per il Rischio Sismico e Vulcanico, Università di Bari, Italy ;Giampiccolo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Martinez-Arevalo, C.; Departamento de Volcanología, Museo Nacional de Ciencias Naturales, CSIC, Madrid Spain ;Patanè, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Romeo, A.; Dipartimento di Geologia e Geofisica & Centro Interdipartimentale per il Rischio Sismico e Vulcanico, Università di Bari, Italy; ; ; ; A crucial point in the analysis of tectonic earthquakes occurring in a volcanic area is the inference of the orientation of the structures along which the ruptures occur. These structures represent zones of weakness which could favor the migration of melt toward the surface and the assessment of their geometry is a fundamental step toward efficient evaluation of volcanic risk. We analyzed a high-quality dataset of 171 lowmagnitude, tectonic earthquakes that occurred at Mt. Etna during the 2002–2003 eruption. We applied a recently developed technique aimed at inferring the source parameters (source size, dip and strike fault) and the intrinsic quality factor Qp of P waves from the inversion of rise times. The technique is based on numerically calibrated relationships among the rise time of first P waves and the source parameters for a circular crack rupturing at a constant velocity. For the most of the events the directivity source effect did not allow us to constrain the fault plane orientation. For a subset of 45 events with well constrained focal mechanisms we were able to constrain the “true” fault plane orientation. The level of resolution of the fault planes was assessed through a non linear analysis based on the random deviates technique. The significance of the retrieved fault plane solutions and the fit of the assumed source model to data were assessed through a χ-square test. Most of the retrieved fault plane solutions agree with the geometrical trend of known surface faults. The inferred source parameters and Qp are in agreement with the results of previous studies285 23 - PublicationOpen AccessA first look at the Gargano (southern Italy) seismicity as seen by the local scale OTRIONS seismic network(2014-07)
; ; ; ; ; ;De Lorenzo, S.; Università di Bari "Aldo Moro", Dipartimento di Scienze della Terra e Geoambientali, Bari ;Romeo, A.; Università di Bari "Aldo Moro", Dipartimento di Scienze della Terra e Geoambientali, Bari ;Falco, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Michele, M.; Università di Bari "Aldo Moro", Dipartimento di Scienze della Terra e Geoambientali, Bari ;Tallarico, A.; Università di Bari "Aldo Moro", Dipartimento di Scienze della Terra e Geoambientali, Bari; ; ; ; On April 2013, a local scale seismic network, named OTRIONS, composed of twelve short period (1 Hz) three component seismometers, has been located in the northern part of the Apulia (southern Italy). In the first two months of data acquisition, the network recorded about one hundred very small (ML<2) magnitude earthquakes. A three-layer 1D VP velocity model was preliminarily computed, using the recordings of earthquakes occurred in the area in the period 2006-2012 and recorded by the national seismic network of INGV (Istituto Nazionale di Geofisica e Vulcanologia). This model was calibrated by means of a multi-scale approach, based on a global search of the minimum misfit between observed and theoretical travel times. At each step of the inversion, a grid-search technique was implemented to infer the elastic properties of the layers, by using HYPO71 to compute the forward models. In a further step, we used P and S travel times of both INGV and OTRIONS events to infer a minimum 1D VP velocity model, using a classical linearized inversion approach. Owing to the relatively small number of data and poor coverage of the area, in the inversion procedure, the VP/VS ratio was fixed to 1.82, as inferred from a modified Wadati diagram. The final 1D velocity model was obtained by averaging the inversion results arising from nine different initial velocity models. The inferred VP velocity model shows a gradual increase of P wave velocity with increasing the depth. The model is well constrained by data until to a depth of about 25-30 km.588 219 - PublicationOpen AccessSeismic Envelopes of Coda Decay for Q-coda Attenuation Studies of the Gargano Promontory (Southern Italy) and Surrounding RegionsHere, we describe the dataset of seismic envelopes used to study the S-wave Q-coda attenuation quality factor Qc of the Gargano Promontory (Southern Italy). With this dataset, we investigated the crustal seismic attenuation by the Qc parameter. We collected this dataset starting from two different earthquake catalogues: the first regarding the period from April 2013 to July 2014; the second regarding the period from July 2015 to August 2018. Visual inspection of the envelopes was carried out on recordings filtered with a Butterworth two-poles filter with central frequency fc = 6 Hz. The obtained seismic envelopes of coda decay can be linearly fitted in a bilogarithmic diagram in order to obtain a series of single source-receiver measures of Qc for each seismogram component at different frequency fc. The analysis of the trend Qc(fc) gives important insights into the heterogeneity and the anelasticity of the sampled Earth medium.
32 23 - PublicationOpen AccessSeismic Q estimates in Umbria-Marche (central Italy): hints for the retrieval of a new attenuation law for seismic risk(2015)
; ; ; ; ;Pisconti, A.; Università di Bari, Dipartimento di Scienze della Terra e Geoambientali ;Del Pezzo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Bianco, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;De Lorenzo, S.; Università di Bari, Dipartimento di Scienze della Terra e Geoambientali; ; ; In the Umbria Marche (Central Italy) region an important earthquake sequence occurred in 1997, characterized by nine earthquakes with magnitudes in the range between 5 and 6, that caused important damages and causalities. In the present paper we separately estimate intrinsic- and scattering- Q −1 parameters, using the classical MLTWA approach in the assumption of a half space model. The results clearly show that the attenuation parameters Qi −1 and Qs −1 are frequency dependent. This estimate is compared with other attenuation studies carried out in the same area, and with all the other MLTWA estimates obtained till now in other tectonic environments in the Earth. The bias introduced by the half space assumption is investigated through numerical solutions of the Energy Transport equation in the more realistic assumption of a heterogeneous crust overlying a transparent mantle, with a Moho located at a depth ranging between 35 and 45 km below the surface. The bias introduced by the half space assumption is significant only at high frequency. We finally show how the attenuation estimates, calculated with different techniques, lead to different PGA decay with distance relationships, using the well known and well proven Boore’s method. This last result indicates that care must be used in selecting the correct estimate of the attenuation parameters for seismic risk purposes. We also discuss the reason why MLTWA may be chosen among all the other available techniques, due to its intrinsic stability, to obtain the right attenuation parameters.370 523
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