Effect of ridge topography on earthquake ground motion

The ridge topography can substantially influence seismic ground motion and, in general, causes the amplification of seismic ground motion amplitude at ridges. Fortunately, sets of three-component accelerogram, obtained by the observation arrays for topographic effect at Zigong Xishan, Jiangyou Doutuan and Qingchuan Sanguo from the great Wenchuan earthquake and its aftershocks, provided basic data for analyzing the effect of ridge topography on seismic ground motion. On the base of these acceleration records, peak ground acceleration and response spectrum ratios are calculated, and examined and compared in order to grasp the effect of ridge topography on ground motion. The findings showed that ridge topography has the remarkable effect on seismic ground motion, in which the amplification characteristics varies depending on the shape of ridge topography, and the amplification effect of the horizontal directions are not similar to the vertical direction, and in some periods are even less than 1.0.