Implications of mHVSR Spatial Variability on Site Response Predictability

One-dimensional ground response analyses (GRA) can introduce model error to site response estimates when wave propagation is not dominated by vertically propagating shear waves. We identify sites suitable for GRA based on microtremor horizontal-to-vertical spectral ratios (mHVSRs). We analyzed 300 microtremor recordings from 17 vertical array sites in California, comparing mHVSRs at varying spatial separations. We find that low mHVSR spatial correlation, as measured using Longest Common Subsequence, tends to occur at vertical array sites that are poorly modeled by GRA. Conversely, stronger mHVSR correlations tend to occur at sites where GRA is relatively effective.