Ground Motion at a Semi-Cylindrical Valley Partially Filled with a Crescent-Shaped Soil Layer Under Incident Plane SH Waves

Abstract

To elucidate the ground motion amplification due to soil and topographic effects, an analytical formulation based on wavefunction expansion is derived for the scattering of plane SH waves by a semi-cylindrical valley partially filled with a crescent-shaped soil layer. The site responses consisting of both soil and topographic effects from the partially filled alluvial valley and the pure topographic contribution from the homogeneous valley of the same geometry are calculated and compared. It is found that the soil amplification effects are usually larger than the topographic amplification effects within the alluvial valley, while the topographic effects dominate the amplification pattern of ground motions outside the alluvial valley. Generally, the maximum soil amplification generally far outweighs the maximum topographic amplification. The material parameters and filling degree of the soil layer are found to affect the magnitude and the pattern of ground motion amplitude on the valley surface depending on the irregular topography, the frequency content and obliquity of the wave incidence.