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Main features and recent upgrades of the Site of Italian Strong Motion Accelerograms (SISMA)
No full textEffects of ground motion characteristics on seismic response of earth dams: some remarks on duration parameters and vertical shaking
No full textAcceleration records used as input motion for nonlinear dynamic analyses of earth
dams can significantly affect the outcome of the analyses. The selection of an adequate set
of records is therefore an essential step of the study. Customary approaches rely on
matching the target spectrum and the average response spectrum of the selected records.
Furthermore, vertical motion is often considered to have a modest influence on dam
response. In this paper, FLAC was used to conduct dynamic analyses of an earth dam
located in Central Italy. The response was assessed in terms of permanent crest settlements
and correlation were attempted with several IMs. The analyses were conducted with and
without vertical component of motions. It was found that Arias Intensity may be considered
an additional parameter to guide selection of input motions. The inclusion of the vertical
components lead to a general increase, on average 75%, of the crest settlemen
Evaluation of EC8 site-dependent acceleration response spectra using strong-motion Italian records.
No full textEffects of ground motion characteristics on seismic response of earth dams. Some remarks on duration parameters and vertical shaking
No full textAcceleration records used as input motion for nonlinear dynamic analyses of earth
dams can significantly affect the outcome of the analyses. The selection of an adequate set
of records is therefore an essential step of the study. Customary approaches rely on
matching the target spectrum and the average response spectrum of the selected records.
Furthermore, vertical motion is often considered to have a modest influence on dam
response. In this paper, FLAC was used to conduct dynamic analyses of an earth dam
located in Central Italy. The response was assessed in terms of permanent crest settlements
and correlation were attempted with several IMs. The analyses were conducted with and
without vertical component of motions. It was found that Arias Intensity may be considered
an additional parameter to guide selection of input motions. The inclusion of the vertical
components lead to a general increase, on average 75%, of the crest settlement
Numerical simulation of site effects in the upper Aterno Valley array during the aftershock sequence of the 2009 L'Aquila earthquake
No full textOn April 6th, 2009 a Mw=6.3 earthquake jolted the Abruzzo region of Central Italy, very close to the urban center of L’Aquila.
Availability of high-quality recordings of the mainshock along with several aftershocks makes the seismic sequence the best recorded near-source events in Italy. In the present study, attention is devoted to the strong motion recordings of the upper Aterno River valley array, which is part of the Italian Accelerometric Network (Rete Accelerometrica Nazionale, RAN), deployed NW of L’Aquila. These data provide a better understanding of the role played by site effects in the seismic response of the valley in epicentral area. This was accomplished by comparing recordings with the results of 1D and 2D site response analyses. The subsoil model of the Aterno valley passing through the accelerometric stations was assumed from a previous study and was integrated with the results of dynamic tests carried out on reconstituted samples of coarse materials frequently encountered in the subsoil. First, the ground surface motion computed by assuming linear soil behavior was compared to the small-magnitude (ML=3-3.5) aftershocks recordings. It was found that 2D modeling provides a satisfactory understanding of the amplification phenomena in the array. Moreover, 2D analyses performed slightly better than 1D predictions. Based on this calibration study, further site response analyses were carried out and the computed ground motion was compared with the aftershock recordings of moderate magnitude (MW=4-5.6). In contrast, the results from these events do not show the analogous performance as obtained in the linear range. More specifically, shape of acceleration response spectra is generally satisfactorily simulated whereas discrepancies are observed in terms of
PGA as well as maximum spectral amplitude. It is speculated on the possible explanations of these discrepancies
Site characterization of Italian strong motion recording stations
No full textA dataset of site conditions at 101 Italian ground motion stations with recorded motions has been compiled that includes geologic characteristics and seismic velocities. Geologic characterization is derived principally from local geologic investigations by ENEL that include detailed mapping and cross sections. For sites lacking such detailed geologic characterization, the geology maps of the by Servizio Geologico d'Italia are used. Seismic velocities are extracted from the literature and the files of consulting engineers, geologists and public agencies for 33 sites. Data sources utilized include post earthquake site investigations (Friuli and Irpinia events), microzonation studies, and miscellaneous investigations performed by researchers or consulting engineers/geologists. Additional seismic velocities are measured by the authors using the controlled source spectral analysis of surface waves (SASW) method for 18 sites that recorded the 1997-1998 Umbria Marche earthquake sequence. The compiled velocity measurements provide data for 51 of the 101 sites. For the remaining sites, the average seismic velocity in the upper 30 m (Vs30) is estimated using a hybrid approach. For young Quaternary alluvium, Vs30 an existing empirical relationship for California sites by Wills and Clahan (2006) is used, which we justify by validating this relationship against Italian data. For Tertiary Limestone and Italian Mesozoic rocks, empirical estimates of Vs30 are developed using the available data. This work is also presented in Scasserra et al
SISMA (Site of Italian Strong Motion Accelerograms): a web-database of ground motion recordings for engineering applications
No full textThe paper describes a new website called SISMA, i.e. Site of Italian Strong Motion Accelerograms, which is an Internet portal intended to provide natural records for use in engineering applications for dynamic analyses of structural and geotechnical systems. SISMA contains 247 three-component corrected motions recorded at 101 stations from 89 earthquakes that occurred in Italy in the period 1972-2002. The database of strong motion accelerograms was developed in the framework of a joint project between Sapienza University of Rome and University of California at Los Angeles (USA) and is described elsewhere. Acceleration histories and pseudo-acceleration response spectra (5% damping) are available for download from the website. Recordings can be located using simple search parameters related to seismic source and the recording station (e.g., magnitude, Vsso, etc) as well as ground motion characteristics (e.g. peak ground acceleration, peak ground velocity, peak ground displacement, Arias intensity, etc.)
Database for Earthquake Strong Motion Studies in Italy
No full textWe describe an Italian database of strong ground motion recordings and databanks delineating conditions at the instrument sites and characteristics of the seismic sources. The strong motion database consists of 247 corrected recordings from 89 earthquakes and 101 recording stations. Uncorrected recordings were drawn from public web sites and processed on a record-by-record basis using a procedure utilized in the Next-Generation Attenuation (NGA) project to remove instrument resonances, minimize noise effects through low- and high-pass filtering, and baseline correction. The number of available uncorrected recordings was reduced by 52% (mostly because of s-triggers) to arrive at the 247 recordings in the database. The site databank includes for every recording site the surface geology, a measurement or estimate of average shear wave velocity in the upper 30 m (Vs30), and information on instrument housing. Of the 89 sites, 39 have on-site velocity measurements (17 of which were performed as part of this study using SASW techniques). For remaining sites, we estimate Vs30 based on measurements on similar geologic conditions where available. Where no local velocity measurements are available, correlations with surface geology are used. Source parameters are drawn from databanks maintained (and recently updated) by Istituto Nazionale di Geofisica e Vulcanologia and include hypocenter location and magnitude for small events (M 5.5) and finite source parameters for larger events
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Critical evaluation of Italian strong motion data and comparison to NGA ground motion prediction equations
Full text linkWe describe an Italian database of strong ground motion recordings and databanks delineating conditions at the instrument sites and characteristics of the seismic sources. The strong motion database consists of 236 corrected recordings from 86 earthquakes and 101 recording stations. Uncorrected recordings were drawn from public web sites and were processed on a record-by-record basis using a procedure utilized in the Next-Generation Attenuation (NGA) project to remove instrument resonances, minimize noise effects through low- and high-pass filtering, and baseline correction. The number of available uncorrected recordings was reduced by 52% (mostly because of s-triggers) to arrive at the 236 recordings in the database. The site databank includes for every recording site the surface geology, a measurement or estimate of average shear wave velocity in the upper 30 m (Vs30), and information on instrument housing. Of the 86 sites, 39 have on-site velocity measurements (17 of which were performed as part of this study using SASW techniques). For remaining sites, we estimate Vs30 based on measurements on similar geologic conditions where available. Where no local velocity measurements are available, correlations with surface geology are used. Source parameters are drawn from databases maintained (and recently updated) by Istituto Nazionale di Geofisica e Vulcanologia and include hypocenter location and magnitude for small events (M < 5.5) and finite source parameters for larger events.Ground motion prediction equations (GMPEs) have recently been developed in NGA project that are intended for application to shallow crustal earthquakes in tectonically active regions. We investigate the compatibility of those models with respect to magnitude-, distance-, and site-scaling implied by Italian strong motion data. This is of interest because (1) the Italian data is principally from earthquakes in extensional regions that are poorly represented in the NGA dataset and (2) past practice in Italy has been to use local GMPEs based on limited data sets which cannot resolve many source, path, and site effects known to be significant. We find that the magnitude scaling implied by the Italian data is compatible with the NGA relations. However, the Italian data attenuate faster than implied by the NGA GMPEs at short periods, and the differences are statistically significant for three of four relations. Three regression coefficients are re-evaluated for the three affected NGA GMPEs to reflect the faster attenuation; a constant term, a geometric spreading and anelastic attenuation term, and a source depth term. The scaling of ground motion with respect to site shear wave velocity is consistent between the NGA models and Italian data. Moreover, the presence of nonlinearity in the Italian data is confirmed and found to be generally compatible with what is provided by NGA site terms. The scatter of Italian data is much higher than in the NGA models, although only the intra-event error is sufficiently well established by the data to justify modification of NGA models. On the basis of these findings, we recommend that NGA relations, with the aforementioned minor modifications, be used to evaluate median ground motions for seismic hazard analysis in Italy
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