Spatial variations in seismic motions

A method for evaluating the spatial variations in strong seismic motions for a linear, homogeneous, and horizontally stratified soil layer system is presented. The procedure accounts for the focal depth and the epicentral distance, the corresponding angle of incidence, and the relative contributions of both shear and Rayleigh waves. The inclined propagation of shear waves is studied using the multiple reflection refraction theory. The range of possible values of Rayleigh wave phase velocity in the soil layer system is determined, and using an averaging procedure the Rayleigh wave amplification factors are computed. The influences of various factors on the spatial variations in seismic response are discussed. The method is general so that it can be used for various problems involving spatial motion computations. The application of the method in computing the responses of a soil–pile system is described and some typical results given.