Models for topographic ground motion amplification based on finite element analyses considering topographic features and ground motions in Japan

Surface topographic irregularities can alter ground motion. In this study, we investigated the influence of various topographic factors such as relative elevation, slope angle, and curvature on ground-motion amplification. A finite element analysis with absorbing boundary layer was performed using actual topographic data and ground motion data from earthquakes of magnitude 3.8–9 recorded in Japan. To identify the effect of wave velocity on ground motion amplification, we considered the variability in topography and three sets of shear and longitudinal wave velocities by considering five cross-sectional profiles for the topographic models in the numerical analyses. We demonstrate that the topographic amplification factor, which is the ratio of the estimated spectral acceleration on the surface to the median spectral acceleration within the entire surface domain, is significantly influenced by curvature and relative elevation. Furthermore, we have proposed models that estimate ground-motion amplification using the two topographic factors—curvature and relative elevation—as variables.