Third International Symposium on the Effects of Surface Geology on Seismic Motion ROBUSTNESS OF THE H/V RATIO PEAK FREQUENCY TO ESTIMATE 1D RESONANCE FREQUENCY

Abstract

ABSTRACT - The H/V method has the potential to significantly contribute to site effects evaluation, in particular in urban areas. Within the SESAME European project (Site EffectS assessment using AMbient Excitations) we investigate the nature of ambient seismic noise in order to assess the reliability of this method. Through 1D seismic noise modeling, we simulate the ambient noise for a set of various horizontally stratified structures. We perform array analysis (f-k) for both vertical and horizontal synthetics and estimate the contribution of different seismic waves (body/surface waves, Rayleigh/Love waves) at the H/V peak frequency. We show that the very common assumption according which almost all the noise energy would be carried by fundamental mode Rayleigh waves is not justified. The proportion of different waves is dependent on site conditions, especially the impedance contrast. However, for the 1D horizontally layered media presented here, the H/V peak frequency always provides a good estimate of the fundamental resonance frequency whatever the H/V peak origin (Rayleigh waves ellipticity, Airy phase of Love waves, S-wave resonance). We also show that the relative proportion of Love waves in ambient noise controls the amplitude of the H/V peak