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LCPC & LGIT, Grenoble, France
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- PublicationOpen AccessEstimation of topographical effects at Narni ridge (Central Italy): comparisons between experimental results and numerical modelling(2011-08)
; ; ; ; ; ; ; ; ;Lovati, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Bakavoli, M.; International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran ;Massa, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Ferretti, G.; Università degli studi di Genova, Dip.Te.Ris., sezione de Geofisica, Genova, Italy ;Pacor, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Paolucci, R.; Dipartimento di Ingegneria Strutturale, Politecnico di Milano, Milano, Italy ;Haghshenas, E.; International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran ;Kamalian, M.; International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran; ; ; ; ; ; ; In the present work the seismic site response of Narni ridge (Central Italy) is evaluated by comparing experimental results and numerical simulations. The inhabited village of Narni is located in central Apennines at the top of a steep massive limestone ridge. From March to September 2009 the site was instrumented with 10 weak-motion stations, 3 of which located at the base of the ridge and 7 at the top. The velocimetric network recorded 642 events of ML up to 5.3 and hypocentral distance up to about 100 km. The great amount of data are related to the April 2009 L’Aquila sequence. The site response was analyzed using both reference (standard spectral ratio, SSR) and non reference spectral techniques (horizontal to vertical spectral ratio, HVSR). Moreover directional analyses were performed in order to evaluate the influence of the ridge orientation with respect to the selected sourcesite paths. In general the experimental results show amplification factors for frequencies between 4 and 5Hz for almost all stations installed along the crest. The SSR technique provides amplification factors up to 4.5 in a direction perpendicular to the main elongation of the ridge. The results obtained from the data analyses were used as a target for bidimensional and tridimensional numerical simulations, performed using a hybrid finite-boundary element method and a boundary element method for 2D and 3D modelling, respectively. In general, the results obtained through numerical simulation fit well the experimental data in terms of range of amplified frequencies, but they underestimate by a factor of about 2 the observed amplifications.209 352 - PublicationOpen AccessSesame Project - Deliverable D04-04 - Report of the WP04 H/V Technique : Empirical Evaluation - Homogeneous Data Set of Noise and Earthquake Recordings at Many Sites(2003-07)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Atakan, Kuvvet; University of Bergen, Norway ;Azzara, Riccardo Mario; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Bard, Pierre-Yves; LGIT, Grenoble, France ;Cara, Fabrizio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Cultrera, Giovanna; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Dimitriu, Petros; ITSAK, Thessaloniki, Greece ;Duval, Anne-Marie; CETE, Nice, France ;Faeh, Donat; ETHZ, Zurich, Swiss ;Di Giulio, Giuseppe; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Hagshenas, Ebrahim; LGIT, Grenoble, France ;Havskov, Jens; University of Bergen, Norway ;Koller, Martin; Resonance, Geneva, Swiss ;Pagani, Marco; CNR-IDPA, Milan, Italy ;Panou, Areti; ITSAK, Thessaloniki, Greece ;Papaioannou, Christos; ITSAK, Thessaloniki, Greece ;Rovelli, Antonio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Savvaidis, Alexandros; ITSAK, Thessaloniki, Greece ;Spohler, Eva; ETHZ, Zurich, Swiss ;Tento, Alberto; CNR-IDPA, Milan, Italy ;Daminelli, Rossella; CNR-IDPA, Milan, Italy ;Marcellini, Alberto; CNR-IDPA, Milan, Italy ;Theodoulidis, Nikos; ITSAK, Thessaloniki, Greece ;Zacharopoulos, Stratos; ITSAK, Thessaloniki, Greece; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; In this Report the homogeneous data set of earthquake and noise recordings at many sites that is generated under the framework of the SESAME Project (Site Effects Assessment Using Ambient Excitations, EC- RGD, Project No. EVG1-CT-2000-00026 SESAME), Task A (H/V technique), Work Package 04 (WP04– H/V Technique: Empirical Evaluation), is presented. Three main topics are included in the Report: (a) The Standard Information Sheet (SIS) structure, (b) The SESAME Ascii Format (SAF) files, and (c) The SESAME SIS-database. The SIS compiled in this sub-task and SAF format adopted for all data, constitute a homogeneous data set to be processed for further scientific results in the framework of the WP04. In addition, the SIS-database is going to facilitate data selection and management.284 441 - PublicationRestrictedEmpirical evaluation of microtremor H/V spectral ratio(2008-02-08)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Haghshenas, E.; International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran ;Bard, P. -Y.; Laboratoire de Geophysique Interne et Tectonophysique, Université Joseph Fourier, Grenoble, France ;Theodulidis, N.; ITSAK Institute of Engineering Seismology and Earthquake Engineering, Tessaloniki, Greece ;Atakan, K.; University of Bergen ;Cara, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Cornou, C.; Laboratoire de Geophysique Interne et Tectonophysique, Université Joseph Fourier, Grenoble, France ;Cultrera, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Di Giulio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Dimitriu, P.; ITSAK Institute of Engineering Seismology and Earthquake Engineering, Tessaloniki, Greece ;Fäh, D.; ETHZ ;De Franco, R.; CNR-IDPA ;Marcellini, A.; CNR-IDPA ;Pagani, M.; CNR-IDPA ;Rovelli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Savvaidis, A.; ITSAK Institute of Engineering Seismology and Earthquake Engineering, Tessaloniki, Greece ;Tento, A.; CNR-IDPA ;Vidal, S.; CETE-Nice ;Zacharopoulos, S.; ITSAK Institute of Engineering Seismology and Earthquake Engineering, Tessaloniki, Greece; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The objective of this work is to perform a purely empirical assessment of the actual capabilities of the horizontal-to-vertical (H/V) spectral ratio technique to provide reliable and relevant information concerning site conditions and/or site amplification. This objective has been tackled through the homogeneous (re)processing of a large volume of earthquakes and ambient noise data recorded by different research teams in more than 200 sites located mainly in Europe, but also in the Caribbean and in Tehran. The original recordings were first gathered in a specific database with information on both the sites and recorded events. Then, for all sites close to an instrumented reference, average site-to-reference spectral ratios (“spectral ratio method” (SSR)) were derived in a homogeneous way (window selection, smoothing, signal-to-noise ratio threshold, averaging), as well as H/V ratios (“HVSRE–RF”) on earthquake recordings. H/V ratios were also obtained from noise recordings at each site (either specific measurements, or extracted from pre- or post-event noise windows). The spectral curves resulting from these three techniques were estimated reliable for a subset of 104 sites, and were thus compared in terms of fundamental frequency, amplitude and amplification bandwidth, exhibiting agreements and disagreements, for which interpretations are looked for in relation with characteristics of site conditions. The first important result consists in the very good agreement between fundamental frequencies obtained with either technique, observed for 81% of the analyzed sites. A significant part of the disagreements correspond to thick, low frequency, continental sites where natural noise level is often very low and H/V noise ratios do not exhibit any clear peak. The second important result is the absence of correlation between H/V peak amplitude and the actual site amplification measured on site-to-reference spectral ratios. There are, however, two statistically significant results about the amplitude of the H/V curve: the peak amplitude may be considered as a lower bound estimate of the actual amplification indicated by SSR (it is smaller for 79% of the 104 investigated sites), and, from another point of view, the difference in amplitude exhibits a questioning correlation with the geometrical characteristics of the sediment/basement interface: large SSR/HV differences might thus help to detect the existence of significant 2D or 3D effects.272 31 - PublicationOpen AccessEMPIRICAL EVALUATION OF THE HORIZONTAL-TO-VERTICAL SPECTRAL RATIO TECHNIQUE: RESULTS FROM THE “SESAME” PROJECT(2004-08-01)
; ; ; ; ; ; ; ; ;SESAME Team ;Theodulidis, Nikos; ITSAK, Thessaloniki, Greece ;Cultrera, Giovanna; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Tento, Alberto; IDPA-CNR, MIlan, Italy ;Faeh, Donat; ETHZ, Zurich, Swiss ;Atakan, Kuvvet; University of Bergen, Norway ;Bard, Pierre-Yves; LCPC & LGIT, Grenoble, France ;Panou, Areti; ITSAK, Thessaloniki, Greece ;Haghshenas, Ebrahim; LCPC & LGIT, Grenoble, France ;SESAME Team; Various; ; ; ; ; ; ; ; In order to empirically evaluate the horizontal-to-vertical (H/V) spectral ratio technique, ambient noise measurements performed in about two hundred sites mainly in Europe where weak or/and strong motion data was recorded. Standard Information Sheets (SIS) and earthquake information data were included in the SESAME [Site EffectS assessment using AMbient Excitations] project database, specially designed to facilitate data selection. All noise recordings were processed with JSESAME software to calculate (H/V) spectral ratio, whereas weak and strong motion earthquake recordings were processed with a similarly standardized procedure. For the latter, (H/V) receiver function for all sites were calculated. Experimental site transfer functions obtained from earthquake recordings were compared with the (H/V) spectral ratios from noise recordings in terms of fundamental frequency, amplification bandwidth and amplification level. Similarities and differences between (H/V) spectral ratio of noise and earthquake recordings are presented and discussed. In addition, a dense grid of noise measurements were performed within urban environment of cities affected by strong earthquake (Greece: Thessaloniki, Kalamata, Italy: Palermo). It seems that the (H/V) spectral ratio may satisfactorily indicate areas favorable to the occurrence of higher damage in urban environment. However, quantitative correlation between (H/V) spectral ratio properties and damage distribution (macroseismic intensity, damage grades) in some cases, is difficult to be established given the complexity of parameters involved.278 627