Earthquake wave propagation in layered media by boundary integral methods: Fid-Bau Portal

Earthquake wave propagation in layered media by boundary integral methods

Hadley, P.K. / Askar, A. / Cakmak, A.S.

Abstract The authors have previously presented work on the use of boundary methods to solve steady-state wave scattering problems in two-dimensional homogenous systems and on the use of these solutions with Fourier transforms to solve problems of transient input waves. This paper extends that work to nonhomogeneous systems. The methodology is now applicable to profiles with various material parameters in media bounded by irregularly shaped interfaces subjected to transient or periodic incident waves of any form. The profiles which can be solved are layers of finite extent, layers of infinite extent, cavities, inclusions of different materials, lenses, cases of three media and three interfaces meeting at a single point, and any combination thereof. The paper presents the basic equations of wave propagation in a single medium, the extension of these equations to multiple media, and the methodology of correcting for the truncation of the numerical portions of a problem. Using these techniques, several simple geometries are solved and the solutions are computed to closed-form solutions when available. Th comparisons are good and the value of correcting for the truncation is verified. The methodology is then applied to a test case of real data taken from real earthquake records, to wit: the response of the Santa Felicia earth dam to the San Fernando (1971) earthquake. The comparison is good in the time domain but in the frequency domain shows some inaccuracy at the higher frequencies. This loss of quality is attributed to the fact that a linear elastic system is not a good model for soil response. The final section an initial attempt to examine the effects of some simple damping schemes. Great improvement is shown in the attempt to reproduce numerically the response of the Santa Felicia earth dam.