Effect of lateral inhomogeneity on seismic waves,II. Observations and analyses

Observation has been conducted on soft surface ground with a sloping basement to clarify the effects of lateral inhomogeneity on ground motions and strains induced by seismic waves and to examine the frequency characteristics of the ground surface motions. The scattered Rayleigh wave from the vicinity of the sloping basement has been detected on seismograms and is observed to have a large influence on the ground motions and strains. In this paper the response of the ground is simulated using a hybrid method which combines a particle model and finite element method (FEM). The computed seismograms are in good agreement with observed ones. It is found from the calculations that large ground strains are produced by the scattered Rayleigh waves as well as by the incident shear waves in the surface ground overlying the sloping basement. In addition, the effects of lateral inhomogeneity on an embedded pipeline are examined. The present results are considered to be significant from the viewpoint of earthquake engineering.