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Mercuri, Alessia
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Mercuri, Alessia
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6701477690
38 results
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- PublicationOpen AccessIndagini Geofisiche non invasive nell’area della Basilica di Santa Croce in Gerusalemme, Roma(2022)
; ; ; ; ; La classificazione sismica elaborata nel 2009 dalla regione Lazio (Regione Lazio, 2009) divide il territorio regionale in tre zone sismiche principali (con pericolosità decrescente da 1 a 3) ed in due sottozone (A e B). Il comune di Roma è classificato utilizzando come unità territoriale i municipi, che ricadono in zona sismica 2B, 3A e 3B. In particolare il municipio Roma I, di cui fa parte l’area di indagine, è classificato in zona 3A. La pericolosità sismica di Roma dipende fondamentalmente da eventi regionali di origine appenninica di magnitudo massima compresa tra 7.0 e 7.5 e distanza di alcune decine di chilometri e da eventi legati all’area dei Colli Albani con magnitudo massima compresa tra 5.0 e 5.5 e distanza entro i 20 chilometri (http//esse1-gis.mi.ingv.it) Sebbene i livelli di scuotimento atteso si possano considerare moderati, lo studio della risposta sismica locale dell’area romana può rivestire un certo interesse anche alla luce della presenza di importanti manufatti di elevato interesse storico-artistico che, a causa di una possibile elevata vulnerabilità, possono presentare un certo grado di fragilità e hanno già subito danni derivati da di terremoti storici (Molin et al. 1995; Galli and Molin 2014). Sulla base delle considerazioni esposte il gruppo dell’Istituto Nazionale di Geofisica e Vulcanologia che si occupa di studi di effetti di sito ha realizzato nell’area della Basilica di Santa Croce in Gerusalemme alcune indagini geofisiche non invasive, basate sull’analisi delle vibrazioni ambientali, finalizzate alla valutazione di un profilo di velocità delle onde sismiche nel sottosuolo da utilizzare in un futuro studio sulla risposta simica locale del sito.72 76 - PublicationOpen Access
47 44 - PublicationOpen AccessEvidence of a Low Frequency Wave-Packet Within Records of the 2016 Central Italy Seismic Sequence(2018-04)
; ; ; ; ; ; ; ; ; ; This work focuses on the observation of data recorded by the seismic temporary network installed in the Amatrice area, under the umbrella of the Italian Center for Seismic Microzonation (http://www.centromicrozonazionesismica.it), following the M 6.0 earthquake of August 24, 2016 in Central Italy. The aim was studying the presence of an evident late low frequency wave packet observed in some of the recorded aftershocks. In order to interpret this phenomenon, we combined a beam-forming analysis performed on these data with the statistics on residuals of localizations related to the same events, recorded by the Italian Seismic Network (RSN). The total number of analyzed events, characterized by M≥=3 and epicentral distances between 30 and 55 Km, is 356. By observing the seismic traces of these events there was an evidence, in some of them, of a low frequency packet appearing 10 seconds after the first arrival. The evidence of this packet was correlated with epicentral distance and focal depth. For a subset of stations, considered as an array, a beam-forming analysis was performed by using the ObsPy toolbox (M. Beyreuther et al., 2010). Results of this analysis gave information in terms of slowness and azimuth to distinguish the main seismic phases of the considered events. In addition, by using locations of the RSN records (Chiaraluce et al., 2017), we performed a parallel analysis within the subset of events with clear evidence of the low frequency packet. We relocated these events by using the NonLinLoc code, with a fixed 1D P-wave velocity model, and varying the Vp/ Vs ratio in the range 1.6–2.0. We found that the P phases residuals are not influenced by the Vp/Vs ratio changes whereas the higher the Vp/Vs the lower are the S phases residuals. Higher values of Vp/Vs ratio, fixing Vp values, could mean a decrease of Vs connected to particular effects during the seismic waves path, that are probably due to geological heterogeneities at local or larger scale68 12 - PublicationOpen AccessSite characterization report at the seismic station IV.LNSS – Leonessa (RI)(2020-12)
; ; ; ; ; ; ; ; ; ; ; In this report we present the geological setting and the geophysical measurements and results obtained in the framework of the 2019-2021 agreement between INGV and DPC, called Allegato B2: Obiettivo 1 - TASK 2: Caratterizzazione siti accelerometrici (Responsabili: G. Cultrera, F. Pacor) for the site characterization of station IV.LNSS (Leonessa).103 67 - PublicationOpen AccessEnergetic wave-packet after first P-wave arrival during 2016 Central Italy seismic sequence: results from F-k array analysis in Amatrice area(2017)
; ; ; ; ; ; ; ; ; ; ; ; ; Following the M 6.0 of August 24 2016 Amatrice earthquake, a temporary seismic network was installed in the village of Amatrice, under the umbrella of the Italian Center for Seismic Microzonation (http://www.centromicrozonazionesismica.it), who conducted a preparatory survey to seismic microzonation with other Italian Institutions. This work focuses on data analysis of 7 stations installed in the Amatrice terrace which is representative of the geological condition of the town, with the aim of studying the possible presence of secondary effects during the seismic sequence caused by site conditions. Stiff bedrock outcroppings were also sampled with 2 reference stations. Preliminary analyses carried out on several earthquakes with Ml > 4 highlight the presence of a low frequency phase with a high energy content at 6 -7 seconds after the first P-wave arrival in almost all the recordings. This wave package was observed for the Mw 6.5 of October 30 earthquake and it has the highest amplitude of the entire recordings, having PGA values of 0.5 g and frequency between 2 and 3 Hz. Frequency-wavenumber analysis performed for the 7 stations array gives an important contribution for the interpretation of this phenomenon, showing that the low frequency wave-package for the examined events does not always show back-azimuth and slowness values compatible with the very first portion of the seismic record. It could be associated to the presence of reflected or refracted waves generated by secondary effects as geological or morphological heterogeneities at local or larger scale.67 9 - PublicationOpen AccessSpectral models for ground motion prediction in the L'Aquila region (central Italy): evidence for stress-drop dependence on magnitude and depth(2016)
; ; ; ; ; ; ; ; ; ; ; ;; ; ; ;; In this study we derive a spectral model describing the source, propagation and site characteris- tics of S waves recorded in central Italy. To this end, we compile and analyse a high-quality data set composed of more than 9000 acceleration and velocity waveforms in the local magnitude (Ml) range 3.0–5.8 recorded at epicentral distances smaller than 120 km. The data set spans the time period from 2008 January 1 to 2013 May 31, and includes also the 2009 L’Aquila (moment magnitude Mw 6.1, Ml = 5.8) sequence. This data set is suitable for the application of data-driven approaches to derive the empirical functions for source, attenuation and site terms. Therefore, we apply a non-parametric inversion scheme to the acceleration Fourier spectra of the S waves of 261 earthquakes recorded at 129 stations. In a second step, with the aim of defining spectral models suitable for the implementation in numerical simulation codes, we represent the obtained non-parametric source and propagation terms by fitting standard parametric models. The frequency-dependent attenuation with distance r shows a complex trend that we parametrize in terms of geometrical spreading, anelastic attenuation and high- frequency decay parameter k. The geometrical spreading term is described by a piecewise linear model with crossover distances at 10 and 70 km: in the first segment, the spectral ordi- nates decay as r −1.01 while in the second as r −1.68 . Beyond 70 km, the attenuation decreases and the spectral amplitude attenuate as r −0.64 . The quality factor Q(f ) and the high-frequency attenuation parameter k, are Q( f ) = 290 f 0.16 and k = 0.012 s, respectively, the latter being applied only for frequencies higher than 10 Hz. The source spectra are well described by ω2 models, from which seismic moment and stress drops of 231 earthquakes are estimated. We calibrate a new regional relationship between seismic moment and local magnitude that im- proves the existing ones and extends the validity range to 3.0–5.8. We find a significant stress drop increase with seismic moment for events with Mw larger than 3.75, with so-called scaling parameter ε close to 1.5. We also observe that the overall offset of the stress-drop scaling is controlled by earthquake depth. We evaluate the performance of the proposed parametric models through the residual analysis of the Fourier spectra in the frequency range 0.5–25 Hz. The results show that the considered stress-drop scaling with magnitude and depth reduces, on average, the standard deviation by 18 per cent with respect to a constant stress-drop model. The overall quality of fit (standard deviation between 0.20 and 0.27, in the frequency range 1–20 Hz) indicates that the spectral model calibrated in this study can be used to predict ground motion in the L’Aquila region.172 158 - PublicationOpen AccessSite characterization report at the seismic station IT.TSC – Tuscania (VT)(2021-12)
; ; ; ; ; ; ; ; ; 29 9 - PublicationRestrictedCharacterization of earthquake-induced ground motion from the L’Aquila seismic sequence of 2009, Italy(2011-01)
; ; ; ; ; ; ;Malagnini, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Akinci, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Mayeda, K.; Berkeley Seismological Observatory, University of California, Berkeley, CA, USA ;Munafo, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Herrmann, R. B.; Department of Earth and Atmospheric Sciences of Saint Louis University, St. Louis, MO, USA ;Mercuri, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; ;Based only on weak-motion data, we carried out a combined study on region-specific source scaling and crustal attenuation in the Central Apennines (Italy). Our goal was to obtain a reappraisal of the existing predictive relationships for the ground motion, and to test them against the strong-motion data [peak ground acceleration (PGA), peak ground velocity (PGV) and spectral acceleration (SA)] gathered during the Mw 6.15 L’Aquila earthquake (2009 April 6, 01:32 UTC). The L’Aquila main shockwas not part of the predictive study, and the validation test was an extrapolation to one magnitude unit above the largest earthquake of the calibration data set. The regional attenuation was determined through a set of regressions on a data set of 12 777 high-quality, high-gain waveforms with excellent S/N ratios (4259 vertical and 8518 horizontal time histories). Seismograms were selected from the recordings of 170 foreshocks and aftershocks of the sequence (the complete set of all earthquakes with ML ≥ 3.0, from 2008 October 1 to 2010 May 10). All waveforms were downloaded from the ISIDe web page (http://iside.rm.ingv.it/iside/standard/index.jsp), a web site maintained by the Istituto Nazionale di Geofisica e Vulcanologia (INGV). Weak-motion data were used to obtain a moment tensor solution, as well as a coda-based moment-rate source spectrum, for each one of the 170 events of the L’Aquila sequence (2.8 ≤ Mw ≤ 6.15). Source spectra were used to verify the good agreement with the source scaling of the Colfiorito seismic sequence of 1997–1998 recently described by Malagnini et al. (2008). Finally, results on source excitation and crustal attenuationwere used to produce the absolute site terms for the 23 stations located within ∼80 km of the epicentral area. The complete set of spectral corrections (crustal attenuation and absolute site effects) was used to implement a fast and accurate tool for the automatic computation of moment magnitudes in the Central Apennines.413 39 - PublicationOpen AccessSite characterization report at the seismic station IV.INTR – Introdacqua (AQ)(2020)
; ; ; ; ; ; ; ; ; Final report illustrating the site characterization for seismic station IV.INTR122 53 - PublicationOpen AccessSite characterization report at the seismic station IT.FOCC – Foligno (PG) Report di caratterizzazione di sito presso la stazione sismica IT.FOCC – Foligno (PG)(2021)
; ; ; ; ; ; ; ; ; ; ; ; ; Final report illustrating the site characterization for seismic station IT.FOCC43 39