Effect of 2-D Subsurface Heterogeneities on Rocking Ground Motion Induced by Incident Plane P Wave

Abstract

The arrival of seismic waves at the ground causes both translational and rotational motions. Because the rotational ground motions can sometimes be significant to the overall dynamic response of structures and because very little recorded data on these motions exist, various methods to obtain indirect estimates of these motions have been proposed. In this study, an attempt is made to critically examine the ‘single-station’ method when, contrary to assumed homogeneous model of the subsurface, a heterogeneous subsurface is considered. This is done by considering the case of a plane P-wave incident at the surface of a 2-D heterogeneous, elastic medium and by comparing the solution of rocking motion (i.e., rotational motion about a horizontal axis) for this medium with that corresponding to a homogeneous, elastic medium. A perturbation-based method is considered to obtain the solution for the heterogeneous medium case.