Abstract
In this paper, the Aki and Larner method is extended to make it possible to compute seismic motions in a three-dimensional framework. We present several numerical examples of seismic motions in three-dimensional (3-D) sedimentary basins with an arbitrarily-shaped interface, due to a rectangular fault source. These numerical examples are then compared with a 3-D wavefield with a flat-layer subsurface structure quantitatively, and with a two-dimensional (2-D) wavefield with irregular-layer subsurface structures qualitatively. We found the seismic motions of the 3-D sedimentary basin models to be larger in amplitude and longer in duration than those of the flat-layer models, and the waveform duration except for the onset portions of a 3-D wavefield to be quite different from those of a 2-D wavefield. Moreover, we investigate the effects of such parameters as dip angle, epicenter location, and irregular interface shapes, on flat free surface responses. By comparing 3-D and 2-D wavefield seismic motions with irregular-layer subsurface structures due to dip-slip faults, we find that seismic motions in a 3-D wavefield are more varied(depending on the effects of the above parameters) than those of a 2-D wavefield. From these results, we see that the effects of a seismic source and a 3-D irregular subsurface structure must be taken into account when predicting strong ground motions.
