Effect of topography on earthquake ground motions

Abstract

The topography of a region significantly affects the ground motions generated during an earthquake. Due to the computational complexities involved, complete three-dimensional analysis of the effect of topography is not studied in detail. The present study tries to understand this effect by simulating ground motions on three-dimensional ridge and valley using a finite element methodology. Here, first the simulated results from the developed model are compared with the existing analytical expressions for wave propagation in two dimensions (2D). Then, a study is performed with topography profile considered as Gaussian with different source locations. The comparison between the cases is performed based on peak ground displacement (PGD) and peak ground velocity (PGV) amplification ratios. It is noted that the location and amplitude of amplification are related to the relative position and depth of source with respect to topography. The study also attempts to develop a relationship between the amplification ratios and topographic gradient. The developed models can be used as a basis to estimate the possible amplification that can occur at a site due to an earthquake.