Comparison of Different Methods Used to Account for Shear Wave Velocity Variability in 1D Ground Response Analyses

One-dimensional (1D) ground response analyses (GRAs) have generally been found to yield site response predictions that are different than recorded ground motions at many downhole array sites, presumably due to their laterally variable subsurface conditions. While there is no doubt that some sites are indeed too variable to be modeled using 1D GRAs, it is also possible that simple 1D analyses could still be effectively used if spatial variability is accounted for via a rational, site-specific approach. In this study, we test three approaches that can be used to account for spatial variability in 1D GRAs: (1) randomization of shear wave velocity (Vs) profiles; (2) increasing the small-strain damping ratio; and (3) an H/V geostatistical approach for generating site-specific spatially variable Vs profiles. We test these approaches at two downhole array sites so that the 1D GRA results can be compared with recorded ground motions. Of the investigated approaches, we find that the H/V geostatistical approach produces superior results and reproduces phenomena observed in the recorded site response at both downhole array sites. In regard to each of these approaches, we discuss issues that should be resolved to enable their adoption in practice.