PGA-PGV/Vs considered as a stress-strain proxy for predicting nonlinear soil response

In this paper, a relationship proxy for predicting the nonlinear soil responses is proposed by mean of monitoring the variation of shear wave velocity along vertical array. The recent seismic interferometry by deconvolution method is applied to extract the shear-wave velocity profile throughout the soil column. Using synthetic modeling, this method is shown to be a relevant and an efficient solution for assessing the Vs profile along a vertical seismic array. The ratio between particle velocity and the equivalent linear shear-wave velocity, v*/Vs*, is computed between two successive sensors, and is assumed to be a proxy for strain. The particle acceleration, a*, versus v*/Vs* is proposed as a stress-strain representation for nonlinear analysis of soil response. Using centrifuge tests, v*/Vs* is shown to be a good representation for soil strain, and analysis of the variation of v*/Vs* as a function of a* allows the nonlinear soil response to be determined in an earthquake situation. These relationship proxies are finally applied to the Japanese K-NET and KiK-net in-situ data, where Vs30 is used instead of Vs* for practical purposes related to site classification recommendations.