Site effects assessment through historical and instrumental data integration

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 the microtremors horizontal-to-vertical spectral ratio features. The measurements carried out in Palermo generally confirmed the Nakamura method effectiveness. However for two measurement points the microtremor spectral ratio exhibited anomalous features, here explained by an integrated analysis of spectral and historical data.