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Univerista della Calabria, Italy
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- PublicationOpen AccessNoise measurements at seismic array in the drilling site of Bagnolifutura, Campi Flegrei(2013-05)
; ; ; ; ; ; ; ; ; ;Petrosino, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Bianco, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Bobbio, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Castellano, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Cusano, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Del Pezzo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Galluzzo, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;La Rocca, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Maiello, V.; Università degli Studi di Napoli Parthenope; ; ; ; ; ; ; ; In 2012 two seismic surveys were carried out in the area of Bagnolifutura (Campi Flegrei, Naples), with the aim of characterizing the properties of the seismic noise during the drilling activity performed in the framework of the Campi Flegrei Deep Drilling Project (CFDDP; https://sites.google.com/site/cfddpproject/). During the first survey, which was conducted from 2 to 4 April, before the drilling, seven broadband three-component seismometers were installed in two different array configurations. The second survey started on November 26, in concomitance with the drilling operations and fluid injection, and ended on December 5, four days after the end of the drilling, when the maximum depth of 502 m was reached. During this period seven broadband and one short-period three-component sensors were installed. A preliminary spectral analysis was performed on samples of seismic noise; moreover the root mean square of the amplitude of the signals and the polarization parameters were calculated. The preliminary results show similar spectral and polarization features for the data of the two surveys, whereas the amplitude of the seismic noise collected during the second survey is greatly influenced by the bad meteorological conditions. As future development experimental site transfer functions from Nakamura’s technique and surface wave dispersion from array techniques will be calculated to obtain the shallow crustal structure. The results corresponding to the different phases of the drilling activity will be compared, with the aim of establishing if significant variations of the medium properties have occurred during the experiment. Moreover the recorded signals will be deeply investigated in order to detect the eventual occurrence of microseismicity induced by fluid injection and to define its features.776 173 - PublicationOpen AccessLa Rete Sismica Permanente dell'Osservatorio Vesuviano(2001)
; ; ; ; ;Buonocunto, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Capello, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Castellano, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;La Rocca, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; ; A partire dal Febbraio 2000 è stata effettuata la ristrutturazione delle attività di monitoraggio sismologico dell’Osservatorio Vesuviano che ha determinato l’omogeneizzazione tecnologica delle singole reti operanti sulle aree vulcaniche attive napoletane ed a scala regionale inglobandole in un’unica Rete Sismica Permanente a Corto Periodo con le caratteristiche salienti di un’alta standardizzazione dei siti e delle installazioni nonché dell’intera catena strumentale. Questa iniziativa è stata intrapresa per garantire l’ottimale coordinamento delle attività di monitoraggio nonché per migliorare la qualità dei dati raccolti e standardizzare i criteri di installazione delle singole stazioni sismiche. Tenendo presente che la maggior parte delle stazioni è installata all’interno di aree densamente urbanizzate, e quindi caratterizzate da un elevato rumore di fondo, particolare attenzione è stata posta nel posizionamento dei sismometri, migliorando l’accoppiamento con il substrato. E’ stato incrementato, inoltre, il numero delle stazioni installate ottenendo geometrie di rete ottimali per le singole aree sismogenetiche. Sono state realizzate, infine, specifiche procedure per la calibrazione (automatica e periodica) delle catene strumentali per ottenere un controllo costante sui livelli di risposta degli strumenti installati. Un altro passo importante compiuto in quest’anno è stato l’installazione di stazioni della Rete Sismica Digitale a Larga Banda Centralizzata, strumento importante per lo studio di segnali sismici legati all’attività magmatica. In questo rapporto vengono illustrati i criteri di miglioramento ed ottimizzazione seguiti, gli standard qualitativi raggiunti e le schede tecniche di tutte le stazioni della Rete Sismica Permanente.184 944 - PublicationOpen AccessSite effects Estimation and Source_Scaling Dynamics for Local Earthquakes at Mt. Vesuvius, Italy(2006-08-30)
; ; ; ; ; ;Galluzzo, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Del Pezzo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Maresca, R.; Università del Sannio, Benevento, Italy ;La Rocca, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Castellano, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; ; ; Local microearthquakes were used to estimate site effects and source dynamic-scaling characteristics at Mt. Vesuvius, Italy. The selected data set is composed of low magnitude events (1.1 £ Md £ 3.6) recorded in 1996 and 1999 by nine digital shortperiod (1-Hz) seismic stations. Site response was evaluated by analysing data with three different approaches: 1) spectral ratios method of S-waves with respect to the average amplitude spectrum; 2) generalized inversion for site and source from the S-waves; and 3) generalized inversion from the coda waves. The results obtained with all three methods showed amplification of a factor of 1.5-2.5 in the 8-14 Hz frequency band for BKE and SGV sites and an amplification of 3 in a narrow band around 8 Hz for the CDT site. Method 2 allowed simultaneous determination of the source spectral shape for each earthquake. By assuming an w2 source model, we estimated the seismic moment Mo and corner frequency fc. The results show that most of the selected earthquakes are characterized by stress drops of 10 bars. The present results are encouraging for further investigation into the techniques for site-effect evaluation and for improving our knowledge of the scaling law of the source spectrum at Mt. Vesuvius.162 262 - PublicationOpen AccessApplication of the spac method to ambient noise recorded in the vesuvius area (italy)(2006)
; ; ; ; ; ;Maresca, R.; Università del Sannio, Benevento, Italy ;Nardone, L.; Università del Sannio, Benevento, Italy ;Galluzzo, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;La Rocca, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Del Pezzo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; ; ; Noise measurements were recorded using a dense short-period seismic array in Terzigno (Naples), a town that is located about 6 km from the Vesuvius crater. The aim of this study was to calculate a surface velocity model of the area under investigation through the application of the Spatial Autocorrelation (SPAC) method, with the hypotheses that ambient noise is stationary both in time and space, and that it is composed of surface dispersive waves. The correct knowledge of the surface structure is an important goal in site-effects studies. Correlation coefficients were calculated as functions of the azimuth on noise recorded at pairs of equally spaced stations in the frequency range of 1-8 Hz. Then, the spatial average correlation coefficients were compared to estimates over long-term recordings. The results appear to validate the hypothesis that ambient noise can be considered as a stochastic process. The correlation-frequency curves have been fitted to Bessel functions, from which the Rayleigh wave dispersion curve has been calculated. A velocity model has been derived from the dispersion curve using both trial and error and a standard inversion procedure. The results are consistent with those obtained from array measurements in the area in other studies (Scarpa et al., 2003).220 569 - PublicationOpen AccessRete Mobile e Laboratorio Analisi aVanzate (LAV) - Rendiconto II semestre 2007(2008)
; ; ; ; ; ; ; ; ;La Rocca, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Galluzzo, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Castellano, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Ciampi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Bianco, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Del Pezzo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Petrosino, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Cusano, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; ; ; ; ; ; In the text153 206 - PublicationOpen AccessLo studio dei vulcani attivi e delle strutture crostali con reti sismiche temporanee: storia, evoluzione e prospettive della Rete Sismica Mobile dell’Osservatorio Vesuviano (INGV)(2012)
; ; ; ; ;Castellano, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Galluzzo, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;La Rocca, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Capello, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; ; In this paper the history of the Mobile Seismic Network of the Osservatorio Vesuviano (at present Department of Napoli of the Istituto Nazionale di Geofisica e Vulcanologia – INGV) is described. The instrumental development and the main research and monitoring activities since the early 1980’ are reported. Starting from the analog stations with magnetic tape recording to the first digital stations with trigger recording, until the modern multichannel 24bit devices, the technological development of the last 30 years has given a strong contribution to increase the knowledge in the seismology and seismotectonics fields. The Mobile Seismic Network has been engaged in active and passive seismic studies both on volcanic and tectonic areas. Particularly, the contribution of the Mobile Seismic Network for the monitoring of Neapolitan active volcanoes has been very important to improve the Permanent Network. During seismic crises high quality data have been gathered allowing detailed analyses of the seismic activity. Moreover, the time synchronization by means of GPS time code allowed the deployment of the Mobile Network abroad and the collaboration with the main international research institutes. At present, the Mobile Seismic Network of the Osservatorio Vesuviano is developing on multichannel acquisition systems, also in array configuration, to gathered simultaneously seismic signals with a large frequency band.570 480 - PublicationRestrictedTidal Modulation of Nonvolcanic Tremor(2007-11-22)
; ; ; ; ; ;Rubinstein, J. L.; Department of Earth and Space Science, University of Washington, Box 351310, Seattle, WA 98195, USA ;La Rocca, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Vidale, J. E.; Department of Earth and Space Science, University of Washington, Box 351310, Seattle, WA 98195, USA ;Creager, K. C.; Department of Earth and Space Science, University of Washington, Box 351310, Seattle, WA 98195, USA ;Wech, A. G.; Department of Earth and Space Science, University of Washington, Box 351310, Seattle, WA 98195, USA; ; ; ; Episodes of nonvolcanic tremor and accompanying slow slip recently have been observed in the subduction zones of Japan and Cascadia. In Cascadia, such episodes typically last a few weeks, and differ from “normal” earthquakes in their source location and momentduration scaling. The three most recent episodes in the Puget Sound/Southern Vancouver Island portion of the Cascadia subduction zone have been exceptionally well recorded. In each episode, we see clear pulsing of tremor activity with periods of 12.4 and 24-25 hours, the same as the principal lunar and lunisolar tides. This indicates that the small stresses associated with the solid-earth and ocean tides influence the genesis of tremor much more effectively than they do “normal” earthquakes. Because the lithostatic stresses are 105 times larger than those associated with the tides, we argue that tremor occurs on very weak faults.284 27 - PublicationOpen AccessA seismic survey at Colima volcano (Mexico)(2008-04-13)
; ; ; ; ; ; ;Breton, M. ;Orozco-Rojas, J. ;Ibanez, J. ;Veneruso, M. ;Del Pezzo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;La Rocca, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Galluzzo, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Petrosino, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Cusano, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Bianco, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Breton, M.; Observatorio Vulcanologico de Colima – Università di Colima (Mexico) ;Orozco-Rojas, J.; Observatorio Vulcanologico de Colima – Università di Colima (Mexico) ;Ibanez, J.; Instituto Andaluz de Geofisica - Universidad de Granada (Spain) ;Veneruso, M.; Centro Regionale di Competenza “Analisi e Monitoraggio del Rischio Ambientale” (AMRA); ; ; ; ; ; ;Observatorio Vulcanologico de Colima – Università di Colima (Mexico) ;Observatorio Vulcanologico de Colima – Università di Colima (Mexico) ;Instituto Andaluz de Geofisica - Universidad de Granada (Spain)Centro Regionale di Competenza “Analisi e Monitoraggio del Rischio Ambientale” (AMRA)In the period 2-6 April 2007 a seismic survey was carried out at Solfatara Volcano, (Campi Flegrei, Southern Italy) with the aim of inferring the shallow structure and evaluating local site effects. Five circular seismic arrays equipped with 1-Hz 3-component Mark LE3Dlite sensors, were installed in the Solfatara crater. Each array consisted of 4 sensors, 3 of them evenly spaced (120°) around the circumference and the fourth placed at its center. The arrays were designed with radii of 5, 10, 25, 50 and 100 m. Some stations of the arrays shaped two orthogonal profiles of about 250-m-length, roughly oriented in the N-S and E-W directions. A further seismic station was installed outside the crater, on the Eastern rim. The particular geometry of the station deployment was adopted to apply the spatial autocorrelation technique (Aki, 1957) and its modifications (MSPAC, Bettig et al., 2001, CCA, Cho et al., 2004), to the data recorded by each array and to infer shear-wave velocity models for different areas of the crater. Further information about the shallow structure will come from the application of Nakamura’s technique (1989) to microtremor recorded at each sampled site. The two orthogonal profiles oriented N-S and E-W will be useful to map possible variations of the resonance frequencies and amplification values along the N-S and E-W directions. The results of the preliminary spectral analysis of some samples of seismic noise recorded during the 2-6 April 2007 survey at Solfatara Volcano, are already indicative of differences among the spectral content of the microtremor recorded in different areas of the crater. In particular the most evident differences are observed between the recordings of the stations located in the central part of the crater and those deployed in the Northern and Eastern areas. Moreover, the seismic noise recorded outside the crater has spectral characteristics that are very different from those observed for the array stations. The observed differences in the spectral content of the seismic noise could be due both to the presence of horizontal velocity contrasts and to variations of the thickness of the shallower layers. The high density of the deployment and the large number of the sampled sites will allow to obtain a detailed shallow velocity structure, to investigate about the presence (or not) of lateral heterogeneities and to map resonance frequencies and amplifications values in different areas of the crater.154 243 - PublicationOpen AccessArray tecniques and spectral ratios applied to seismic noise to investigate subsoil structures in Campi Flegrei (Italy)(2018-09)
; ;Esposito, Roberta; ; ; ; ; ; ; ; ; ; ; The purpose of this work is to study the subsoil structure (from shallow to deep layers) of the Campi Flegrei area using both spectral ratios and array techniques applied to seismic noise. The dataset consists of seismic noise recorded in the underground by the seismic Array “ARF” and the broadband stations of the mobile network. We estimated the dispersion curves of Rayleigh waves propagating through the array by applying the Frequency–Wavenumber (f-k) technique and the MSPAC method. The phase velocity dispersion curve of the fundamental mode of Rayleigh waves was obtained by plotting the inverse of slowness, as a function of frequency, and selecting the part of the curve bounded by the resolution limits defined through kmin and kmax. For the MSPAC method we divided the array in semi-circular sub arrays called Rings, which radius are defined by the sensor’s spacing, and we calculated the spatial autocorrelation coefficients for all the possible pairs of sensors. Further constrains on the dispersion curves are obtained from the estimate of the phase velocity of transient coherent signals recorded by the array. We used the DINVER computer code to perform a joint inversion of the autocorrelation coefficients, the dispersion curves, the single coherent noise values and the mean HVSR of the mobile network station to obtain a shallow shear wave velocity model for the first 200 m, which is in a good agreement with the stratigraphic information of the wells available in the area. The study of the velocity models is crucial to recognize anomalies due to the presence of fluids connected to the volcanic activity and a high quality characterization of the medium allows us to correctly identify, in the geophysical observables, the contribution of the volcanic source.132 23 - PublicationRestrictedRete Mobile e Laboratorio Analisi aVanzate (LAV) - Rendiconto 2013(2014-03)
; ; ; ; ; ; ; ;Cusano, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Galluzzo, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;La Rocca, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Petrosino, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Bianco, F. ;Castellano, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Del Pezzo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; ; ; ;; In the text262 94