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Fischione, Costantino
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- PublicationOpen AccessTopography effects in the polarization of coda waves: a comparison between surface and deep recordings(2012)
; ; ; ; ; ; ; ; ; ; ; Local and regional earthquakes recorded in 2007 by two seismic arrays at Gran Sasso (Italy), one located at surface and one at 1.4 km depth, have been analyzed. Polarization properties of the seismic wavefield have been estimated at both arrays on a short sliding window and in several frequency bands. Array methods were also applied, and the estimated slowness and backazimuth were used to compute the stacking of phase shifted signals in order to improve the signal to noise ratio. Results of polarization computed over single station and array stacked signals have been compared between the two arrays. A well defined polarization azimuth, roughly perpendicular to the main massif ridges, is evident at surface in a broad frequency band. This is observed for earthquake body waves and coda waves. On the contrary, underground the same effect is slightly visible only at very low frequency.75 34 - PublicationOpen AccessPerformances of the UNDERground SEISmic array for the analysis of seismicity in Central Italy(2006-08)
; ; ; ; ; ; ;Saccorotti, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Di Lieto, B.; Dipartimento di Fisica «E.R. Caianello», Università degli Studi di Salerno, Baronissi (SA), Italy ;Tronca, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Fischione, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Scarpa, R.; Dipartimento di Fisica «E.R. Caianello», Università degli Studi di Salerno, Baronissi (SA), Italy ;Muscente, R.; Parco Scientifico e Tecnologico d’Abruzzo, L’Aquila, Italy; ; ; ; ; This paper presents the first results from the operation of a dense seismic array deployed in the underground Physics Laboratories at Gran Sasso (Central Italy). The array consists of 13 short-period, three-component seismometers with an aperture of about 550 m and average sensor spacing of 90 m. The reduced sensor spacing, joined to the spatially-white character of the background noise allows for quick and reliable detection of coherent wavefront arrivals even under very poor SNR conditions. We apply high-resolution frequency-slowness and polarization analyses to a set of 27 earthquakes recorded between November, 2002, and September, 2003, at epicentral distances spanning the 20-140 km interval. We locate these events using inversion of P- and S-wave backazimuths and S-P delay times, and compare the results with data from the Centralized National Seismic Network catalog. For the case of S-wave, the discrepancies among the two set of locations never exceed 10 km; the largest errors are instead observed for the case of P-waves. This observation may be due to the fact that the small array aperture does not allow for robust assessment of waves propagating at high apparent velocities. This information is discussed with special reference to the directions of future studies aimed at elucidating the location of seismogenetic structures in Central Italy from extended analysis of the micro-seismicity.340 280 - PublicationOpen AccessSlow earthquakes and low frequency tremor along the Apennines, Italy(2008-04)
; ; ; ; ; ; ; ;Scarpa, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Amoruso, A.; Dipartimento di Fisica, Università degli Studi di Salerno, Italy ;Crescentini, L.; Dipartimento di Fisica, Università degli Studi di Salerno, Italy ;Fischione, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Formisano, L. A.; Dipartimento di Fisica, Università degli Studi di Salerno, Italy ;La Rocca, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Tronca, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; ; ; ; ; This paper reviews the main observations on slow earthquakes and low frequency tremor made along the Apennines, the main seismic active zone of Italy. These observations have been made using a geodetic interferometer system operating since 1994 in the underground tunnel of Gran Sasso, central Italy, and an underground seismic array (UNDERSEIS) operating since 2002 in the same environment. The observations made in recent years indicate that both phenomena are quite rare and apparently uncorrelated. Slow earthquakes, mainly recorded in 1997 and occasionally later, have probably been caused by the activity of a shallow fault system located near the interferometers. Until now only one tremor episode characterized by low frequency content and duration of several hours has been detected in January 2004, without any correlations with the occurrence of slow or regular earthquakes. The signal to noise ratio of this event is very low, but the results of our detailed analysis show that its frequency contents and wave field characteristics are compatible with a low frequency non volcanic tremor.260 461