Frequency Response Characteristics for Incident P-SV Waves in Multi-Layered Irregular Strata Including Water-Saturated Layers Using Discrete Wave Number Method.

Abstract

It is important to investigate wave propagation characteristics taking into account the effects of pore-water in, e.g., soft sand layers with topographical and/or subsurface irregularities. To obtain information on the spatial variation of displacements, stresses and pore-water pressures, the authors have extended the Discrete Wave Number Method proposed by Aki and Larner (1970) to the P-SV wave incident problems in multi-layered media with topographical and/or subsurface irregularities including water-saturated layers. This paper first explains the analytical method and then verifies it using numerical examples incorporating spatial variation characteristics of frequency response functions of displacements, stresses and pore-water pressures. The effects of subsurface irregularities on the frequency response are discussed. The response characteristics of an elastic model and a water-saturated model are compared. It is thus confirmed that the Discrete Wave Number Method can be efficiently used to calculate amplifications of ground motions taking into account wavetype coupling and wavenumber coupling in a multi-layered alluvial deposit with subsurface irregularities and a very permeable water-saturated layer.