Effects of the canyon topography on ground motions at the Feitsui damsite

Abstract

Abstract A numerical scheme based on the boundary integral equation formulation is applied to a two-dimensional SH model of the Feitsui canyon to study the effects of the canyon topography on strong ground motion. The medium responses of this model for plane SH waves incident at various angles were calculated in a frequency band ranging from 0 to 6.0 Hz. It appears that the shielding and scattering effects of canyon topography can greatly modify the ground motions. Based on these medium responses, the recorded SH ground motion at one station is considered as the input to simulate the corresponding component at the second station. The observed and the simulated ground motions at the second station show satisfactory agreement in ground displacement and velocity. The simulated accelerations corresponding to the high-frequency part of ground motions did not fit the observations well. This discrepancy shows the limitation of our simplified model, which does not include the effects of the dam and the variation of topography in the third dimension. In order to improve the simulation of ground accelerations, it is necessary to have the 3-D modeling.