Topographic Amplification Factors for Japan Using 2D Finite Element Analysis

It is widely recognized that seismic waves can be amplified or deamplified due to constructive or destructive interference when the waves encounter surface topographic irregularities such as valleys, peaks, and plateaus. These phenomena, termed as topographic effects, are particularly important for the seismically-induced landslide hazard assessment. This study examines influence of various factors such as peak ground acceleration, slope angle, relative elevation, and curvature on ground motion amplifications by performing finite element analyses with realistic topography data (from ASTER Global Digital Elevation Model Version 2) and real ground motions for Japan obtained from the National Research Institute for Earth Science and Disaster Prevention (NIED) strong-motion seismograph networks. The results show that topographic amplification factors (defined as the spectral acceleration estimated for the topography model divided by that estimated for the free-field) are most sensitive to relative elevation and curvature. The predictive models are proposed using those two factors as variables.