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de Lorenzo, Salvatore
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de Lorenzo, Salvatore
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- 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 AccessTime occurrence of earthquake instabilities in rate– and state–dependent friction models(2011)
; ; ; ; ;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; ; ; 149 154 - 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 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 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 AccessTime occurrence of earthquake instabilities in rate– and state–dependent friction models(2011-05)
; ; ; ; ;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; ; ; Since the latter half of last century many studies and laboratory experiments have focused on the understanding of the evolution of frictional strength during sliding events on active faults. Such events may occur through aseismic fault creep, high-velocity slip and, in some cases, as a combination of both. According to the concept that earthquakes are frictional instabilities, their time occurrence may show a periodical pattern (the seismic cycle) whose behavior can be referred to the stick-slip dynamic. The dynamic evolution of a fault is often modeled considering its formal analogy with a physical system known as the spring-slider model (namely, a damped harmonic oscillator). Many experimental studies have been conducted using the spring-slider model, most of them simulating the interaction between slip surfaces with the surrounding elastic medium with a single-degree-of-freedom system. Despite its obvious limitations, such a model has provided important insights on dynamics of stick-slip cycle [Gu et al., 1984; Carlson et al., 1994], nucleation of earthquakes and triggered earthquake phenomena [e.g. Belardinelli et al., 2003]. On the basis of several experimental results on rock friction, Dieterich (1979) and Ruina (1983) formulated rate- and state-dependent friction laws, in which the frictional resistance is expressed through the evolution of the sliding rate and its history. Afterwards, Chester and Higgs (1992) figured out that also the temperature variation, produced by frictional heating, can affect the duration of the seismic cycle and the evolution of the frictional strength as well and consequently they incorporate such a thermal effect, improving the previous Ruina’s constitutive law. The present study is aimed to: 1. investigate the spring-slider physical response depending on the adopted constitutive law; 2. show the influence that the constitutive laws can exert on the time occurrence of a seismic instability and on the seismic cycle duration; 3. compare the constitutive laws in order to show their different features in simulating the evolution of slip velocity, stress drop and seismic cycle.234 152 - PublicationRestrictedQc, Qb, Qi and Qs attenuation parameters in the Umbria–Marche (Italy) region(2013)
; ; ; ;De Lorenzo, S.; Dipartimento di Scienze della Terra e geoambientali, University of Bari ;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; ; The attenuation of coda and S waves has been inferred for the Umbria–Marche region (central Italy) using seismic waveforms collected during the 1997 seismic crisis. The selected dataset is composed of 343 small magnitude (1.4 < ML < 4.2) earthquakes recorded at a temporary array composed of 23 seismic stations. The Sato (1977) method, based on the assumption of single isotropic scattering has been used to infer Qc, considering three different lapse times (20, 30 and 40 s). The coda normalization method (Aki, 1980) has been used to infer Qb. Both Qc and Qb show a clear frequency dependence with a different frequency dependent parameter. The frequency dependence of Qc is comparable with that previously found in the same area and around it. Using the method of Wennerberg (1993), intrinsic and scattering attenuation have been separated. Intrinsic attenuation is found to be close to coda attenuation and dominates over scattering dissipation. Coda Q increases with increasing lapse time but at a rate smaller than that observed in other areas of the Earth. Coda and intrinsic attenuation in the Umbria–Marche region are very high compared to other seismic active regions of the Earth. The retrieved high values of intrinsic attenuation may be explained in terms of the previously hypothesized fluid-pressurized regime of the crust in the central Apennines (Miller et al., 2004).173 21 - PublicationOpen AccessIntrinsic Qp at Mt. Etna from the inversion of rise times of 2002 microearthquake sequence(2006-12)
; ; ; ; ;de Lorenzo, S.; Dipartimento di Geologia e Geofisica, Università degli Studi di Bari, Italy ;Filippucci, M.; Centro Interdipartimentale per la Valutazione e Mitigazione del Rischio Sismico e Vulcanico, Bari, Italy ;Giampiccolo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Catania, Italy ;Patanè, D.; Istituto Nazionale di Geofisica e Vulcanologia, Catania, Italy; ; ; About three-hundred microearthquakes, preceeding and accompanying the 2002-2003 Mt. Etna flank eruption, were considered in this study. On the high-quality velocity seismograms, measurements of the first half cycle of the wave, the so-called rise time τ, were carried out. By using the rise time method, these data were inverted to infer an estimate of the intrinsic quality factor Qp of P waves and of the source rise time τ0 of the events, which represents an estimate of the duration of the rupture process. Two kind of inversions were carried out. In the first inversion τ0 was derived from the magnitude duration of the events, assuming a constant stress drop and Qp was inferred from the inversion of reduced rise times τ−τ0. In the second inversion both τ0 and Qp were inferred from the inversion of rise times. To determine the model parameters that realize the compromise between model simplicity and quality of the fit, the corrected Akaike information criterion was used. After this analysis we obtained Qp=57±42. The correlation among the inferred τ0 and Qp, which is caused by some events which concomitantly have high τ0 (>30 ms) and high Qp (>100) indicates that the technique used is able to model rise time versus travel time trend only for source dimensions less than about 80 m.220 231 - 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 - PublicationRestrictedThermal model of the Vesuvius magma chamber(2006)
; ; ; ; ; ;de Lorenzo, S.; Dipartimento di Geologia e Geofisica, Universita` di Bari, Italy ;Di Renzo, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Civetta, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;D’Antonio, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Gasparini, P.; Universita` Federico II di Napoli, Italy.; ; ; ; A thermal modeling of the Vesuvius is presented, based on its magmatic and volcanic history. A 2D numerical scheme has been developed to evaluate the heat transfer inside and around a magma body, the latent heat of crystallization and the inputs of magma from the asthenosphere to a crustal reservoir. Assuming a ratio >1 between velocities of magma ascending in the conduit and magma laterally displaced in the reservoir, the results indicate that, after 40 ka, the reservoir is vertically thermally zoned. As a consequence it hosts magma batches that can individually differentiate, mix and be contaminated by the crust, and produce the spectrum of isotopic compositions of the Vesuvian products. The thermal model reproduces the geothermal gradient and the brittle-ductile transition (250– 300 C) at 6 km of depth (the maximum depth of earthquake foci) only after 0.5–1 Ma, implying a long lived magma chamber below the volcano.253 50
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