Third International Symposium on the Effects of Surface Geology

The way of interpreting results of ambient vibration based techniques in the context of near surface site structure investigations very often depends on the assumptions about the nature of the wavefield. Taking into account the relative fraction of Rayleigh and Love waves on the horizontal components is important in order to improve the evaluation of H/V spectral ratios by realistic forward modeling. Within this study we employed the modified 3c-SPAC method to determine the Rayleigh to Love wave partitioning at eight different European sites. Site structures, frequency dependence and temporal stationarity were analyzed in order to find characteristic features in the results. We found a dominance of Love waves between 70 and 90 % over a broad frequency range within the reliable band for analysis. In conclusion, there seems to be no systematical effect of the site on the mean level of Love waves. However, we observed deviations from the mean level inside the reliable frequency band. These effects are characterized by a higher variance of the partitioning in the vicinity of the fundamental frequency of the site. This can be attributed to the Rayleigh wave ellipticity, the Airy phase of Love waves and, for some sites, also to deviations from the assumption that surface waves dominate the wavefield.