SEISMIC-WAVES IN A LATERALLY INHOMOGENEOUS LAYERED MEDIUM .2. ANALYSIS

Seismic wave scattering representation for the layered half-space with lateral inhomogeneities subjected to a seismic dislocation source has been formulated in the companion paper with the use of first-order pe rturbation (Born-type approximation) technique. The total wavefield is obtained as a superposition of the mean and the scattered wave fields , which are generated, respectively, by a series of double couples of body forces equivalent to the seismic dislocation source and by fictit ious body forces equivalent to the existence of the lateral inhomogene ities in the layered half-space. The responses in both the mean and th e scattered wave fields are found with the aid of an integral transfor m technique and wave propagation analysis. The characteristics of the scattered waves and their effects on the mean waves or corresponding i nduced ground and/or underground mean responses are investigated in th is paper. In particular, coupling phenomena between P-SV and SH waves and wave number shifting effects between the mean and the scattered wa ve responses are presented in detail. With the lateral inhomogeneities being assumed as a homogeneous random field a qualitative analysis is provided for estimating the effects of the lateral inhomogeneities on the ground motion, which is related to a fundamental issue: whether a real earth medium can or cannot be approximately considered as a late rally homogeneous layer. The effects of the lateral inhomogeneities on the ground motion time history are also presented as a quantitative a nalysis. Finally, a numerical example is carried out for illustration purposes.