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Romeo, R.
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- PublicationOpen AccessA study of local site effects in Benevento(Southern Italy) by the analysis of seismic records of explosions(1995-09)
; ; ; ; ; ; ; ; ; ; ;Iannaccone, G.; Dipartimento di Geofisica e Vulcanologia, Università di Napoli, Italy ;Improta, L.; Dipartimento di Geofisica e Vulcanologia, Università di Napoli, Italy ;Biella, G.; Istituto per le Ricerche sul Rischio Sismico, Milano, Italy ;Castellano, M.; Osservatorio Vesuviano, Ercolano, Napoli, Italy ;Deschamps, A.; Institut de Geodynamique, C.N.R.S., Universite de Nice, Sophia-Antipolis, France ;De Franco, R.; Istituto per le Ricerche sul Rischio Sismico, Milano, Italy ;Malagnini, L.; Istituto Nazionale di Geofisica, Roma, Italy ;Mirabile, L.; Istituto di Oceanologia, Istituto Universitario Navale, Napoli, Italy ;Romeo, R.; Servizio Sismico Nazionale, Roma, Italy ;Zollo, A.; Dipartimento di Geofisica e Vulcanologia, Università di Napoli, Italy; ; ; ; ; ; ; ; ; In this paper we evalllate the seismic amplification effects in the town of Benevento llsing records of an explo- sion of 500 kg fired at abollt 7 km. Seismic records were obtained at 43 selected sites in the city by digital three-component stations. A data selection performed on the signal-to-noise ratio reduced the available data to 26 stations. We used the spectral ratio techniques to evaluate the amplification effects of each recording site compared both to the average spectrum calculated over 26 stations and to a reference seismic station. The shapes of the spectral ratios were classified according to the geological characteristics of the site. A characteristic shape of the spectral ratio was observed to be related to the specific structure of the subsoil. In particular, the sites on basin sediments (Lagonegro Unit) and Middle Pleistocene conglomerates failed to show amplification effects; the sites on thick alluvial deposits showed amplification in the 5-9 Hz range; finally, sites on alluvial-lacustrine deposits amplified the seismic signal at frequencies depending on the characteristics and the thickness of the deposit. In addition, damage distribution caused by the 1688 earthquake in Benevento was related to the thickness of the surface layers in the ancient built-up area of the town. The study of the spectral ra- tios showed that these deposits amplify ground motion at frequencies between 9 and 12 Hz, i.e. frequencies close to the natural period of the most widespread buildings at that time in Benevento. Geological and seismic data were jointly used to carry out a zonation of the urban area of Benevento on the basis of homogeneous seismic responses. The validity of this analysis is limited to the main frequency band and amplitude of ground motion produced by the explosions.196 570 - PublicationOpen AccessCaratterizzazione della risposta sismica nella città di Benevento.(1994-12)
; ; ; ; ; ; ; ; ;Iannaccone, G.; Università di Napoli "Federico II" ;Improta, L.; Università di Napoli "Federico II" ;Romeo, R.; Servizio Sismico Nazionale, Roma ;Biella, G.; Istituto di Ricerca sul Rischio Sismico, CNR, Milano ;De Franco, R.; Istituto di Ricerca sul Rischio Sismico, CNR, Milano ;Basili, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Castellano, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Deschamps, A.; Institut de Géodynamique, Valbonne; ; ; ; ; ; ; L'ampiezzà de1 moto del suolo, ed il suo contenuto in frequenza, alla súpeúcie della TerIa dípede dale caratte stiche della, sorgente sismica e dalle proprietà meccaniche del úezzo in cui si propagano le onde sismiche. In pa.rtico lare, gli strati pmssimi alla superficie possono modifrcare in modo sigdficativo il segnale sismlco. InJatti la presenza, di uno strato con un fo e contraato di im pedenza, spetto ad un basarnento sottostànte prÌò indurc etretti di risonanza alterando sensibilmente il livelo di anpiezza, il conterùto in Îrequenza e la, durata delle oscilla.zioni del suolo. Un esempio estîemo di questo fenomeno è stato evidenziatoi n occasiored el terremoto di Michoacan,M essico,d el 1985.Q uesto evento, pur essendo a-r.venuto ad alcune centinaia di chilometri da.lla capitale, ha, eccitato con il pe.iodo proprio di oscillnzioÈe( cilca 2 secondi)i depositi di riempimento di un antico lago prosciugato, su cui è costruita parte di Città, del Messico, pmvocaùdo iI crollo di nurerosi edifici e misliaia di morti (Singh et al., 1988177 145 - PublicationOpen AccessA P-wave velocity model of the upper crust of the Sannio region (Southern Apennines, Italy)(1998-10)
; ; ; ; ; ; ; ; ; ; ;Iannaccone, G.; Osservatorio Vesuviano, Ercolano, Napoli, Italy ;Improta, L.; Dipartimento di Scienze Fisiche, Universitá di Napoli ;Capuano, P.; Osservatorio Vesuviano, Ercolano, Napoli, Italy ;Zollo, A.; Dipartimento di Scienze Fisiche, Universitá di Napoli ;Biella, G.; Istituto per le Ricerche sul Rischio Sismico, Milano, Italy ;De Franco, R.; Istituto per le Ricerche sul Rischio Sismico, Milano, Italy ;Deschamps, A.; Institut de Geodynamique, CNRS, Université de Nice, Sophia-Antipolis, France ;Cocco, M.; Istituto Nazionale di Geofisica, Roma, Italy ;Mirabile, L.; Istituto di Oceanologia, Istituto Universitario Navale, Napoli, Italy ;Romeo, R.; Servizio Sismico Nazionale, Roma, Italy; ; ; ; ; ; ; ; ; This paper describes the results of a seismic refraction profile conducted in October 1992 in the Sannio region, Southern Italy, to obtain a detailed P-wave velocity model of the upper crust. The profile, 75 km long, extended parallel to the Apenninic chain in a region frequently damaged in historical time by strong earthquakes. Six shots were fired at five sites and recorded by a number of seismic stations ranging from 41 to 71 with a spacing of 1-2 km along the recording line. We used a two-dimensional raytracing technique to model travel times and amplitudes of first and second arrivals. The obtained P-wave velocity model has a shallow structure with strong lateral variations in the southern portion of the profile. Near surface sediments of the Tertiary age are characterized by seismic velocities in the 3.0-4.1 km/s range. In the northern part of the profile these deposits overlie a layer with a velocity of 4.8 km/s that has been interpreted as a Mesozoic sedimentary succession. A high velocity body, corresponding to the limestones of the Western Carbonate Platform with a velocity of 6 km/s, characterizes the southernmost part of the profile at shallow depths. At a depth of about 4 km the model becomes laterally homogeneous showing a continuous layer with a thickness in the 3-4 km range and a velocity of 6 km/s corresponding to the Meso-Cenozoic limestone succession of the Apulia Carbonate Platform. This platform appears to be layered, as indicated by an increase in seismic velocity from 6 to 6.7 km/s at depths in the 6-8 km range, that has been interpreted as a lithological transition from limestones to Triassic dolomites and anhydrites of the Burano formation. A lower P-wave velocity of about 5.0-5.5 km/s is hypothesized at the bottom of the Apulia Platform at depths ranging from 10 km down to 12.5 km; these low velocities could be related to Permo-Triassic siliciclastic deposits of the Verrucano sequence drilled at the bottom of the Apulia Platform in the Apulia Foreland.195 484