Spatially-varying Non-stationary Subsurface Motions in Multi-Layered Soil Medium

Abstract

This paper presents simulations of spatially-varying non-stationary earthquake motions at subsurface sites in multi-layered soil medium. The motions are compatible to the sites in terms of both spatial-variation and earthquake energy. The stochastic Fourier spectrum characterizes the bedrock energy distribution. The bedrock and subsurface motions are related by a transfer function. The spatial-variation is represented by the existing lagged coherency functional forms and their site-compatible parameters and uniform and random phases. Wavelet transform is introduced to investigate simultaneously the temporal and spectral variation of the simulated motions. In the case study, horizontal motions of three sites at ground surface and at a depth of 20 m in a two layered soil medium above the bedrock depth of 50 m and corresponding to an earthquake moment magnitude of 5.5 are simulated. As subsurface motions are hardly recordable, the simulated motions are useful for the analyses of underground structures and soil-structure interactions.