A numerical study of effects of valley-weathering and valley-shape-ratio on the ground motion characteristics

Abstract

A study of combined effects of valley-weathering and valley-shape-ratio on the ground motion characteristics and associated differential ground motion (DGM) is documented in this paper. In order to properly quantify the weathering effects, a forth-order-accurate staggered-grid viscoelastic time-domain finite-difference program has been used for the simulation of SH-wave responses. Simulated results revealed that the defocusing caused by valley is frequency-independent in contrast to the ridge-focusing. A decrease of average spectral amplification (ASA) with an increase of shape-ratio of the non-weathered triangular and elliptical valleys was obtained. Overall, the amplification and de-amplification pattern was larger in case of triangular valleys as compared to the elliptical valleys. It can be concluded that the dwelling within or near the top-corners of weathered valleys may suffer more damage as compared to their surroundings. A weathered triangular valley with large shape-ratio may cause unexpected damage very near its top-corners since both the ASA and DGM are largest.