Search results for "Microtremors"
showing 3 items of 3 documents
Site effects assessment through historical and instrumental data integration
2006
ABSTRACT This work illustrates the historical data contribution to the analysis of the microtremor survey results carried out in May 2003 in the city of Palermo by the Istituto Nazionale di Geofisica e Vulcanologia and the Dipartimento di Geologia e Geodesia – University of Palermo. The microtremor survey has been carried out within the project SESAME (Site EffectS assessment using AMbient Excitations) funded by the European Commission, devoted to test the effectiveness of the seismic noise, and in particular of Nakamura technique, in the site effects assessment. The Nakamura technique singles out zones characterized by a near-surface geology suitable to produce site effects, by exploiting …
Contribution of the cluster analysis of HVSR data for near surface geological reconstruction
2015
The use of HVSR technique allows in many cases (Bonnefoy-Claudet et al. 2006) to obtain detailed reconstruction of the roof of the seismic bedrock (Di Stefano et al. 2014) and to identify areas with similar seismic behaviour. Theoretical considerations (Nakamura 1989) and experimental tests showed that amplification of horizontal motions between bottom and top of a sedimentary cover is well related to the ratio between the spectra of the horizontal and vertical components of the ground velocity (Nakamura 2000). This ratio is a measure of ellipticity of Rayleigh wave polarization, overlooking Love and body waves contribution. Assuming that subsoil can be represented as a stack of homogeneous…
Microtremor Measurements in the City of Palermo, Italy: Analysis of the Correlation between Local Geology and Damage
2008
Abstract This study presents the results of 90 seismic ambient noise measurements in Palermo, the main city of Sicily (Italy). The dataset has been processed using the horizontal-to-vertical spectral ratio (HVNSR) technique and interpreted in terms of local geology, which is characterized by the presence of alluvial sediments of two riverbeds masked by urbanization since the seventeenth century. HVNSRs show significant variations in the study area: when the transition stiff to soft is crossed, a typical spectral peak appears in the HVNSRs, mostly in the frequency band 1–2 Hz, and exceeding a factor of 3 in amplitude. Using available information on subsurface geological structure, we compute…