Comparing depth-to-bedrock and fundamental-frequencies as supplement proxies to v_s30 in site response evaluation

Alternative proxies as supplemental to V_S30 for site-response predictions in Israel are examined. We use a large database of local velocity profiles to compute the expected amplifications, due to the lack of empirical ground-motion measurements. Amplification is computed with respect to a new generic rock profile, defined as part of this study. We test the correlation of eight different site proxies with the computed amplification factors and show that the average shear-wave velocity (V_S30 ) best describes amplification at short spectral periods, while some measure of depth is needed to also capture amplification at long spectral periods. We discuss optional depth proxies, including depth to a certain velocity (e.g. Z₁₁₀₀), as well as peak frequencies in the acceleration transfer function which are highly correlated with depth. The selected proxy must be a combination of high statistical correlation as well as applicability for the local engineering community.