HR: 0800h
AN: S21B-0219    [Abstracts]
TI: Earthquake site effect modeling in sedimentary basins using IBEM-FMM
AU: * Lee, J
EM: lee@geol.binghamton.edu
AF: Department of Geological Sciences, Binghamton University PO Box 6000, Binghamton, NY 13902-6000 United States
AU: Barker, J S
EM: barker@geol.binghamton.edu
AF: Department of Geological Sciences, Binghamton University PO Box 6000, Binghamton, NY 13902-6000 United States
AB: The Boundary Element Method (BEM) has been applied to simulate seismic wave propagation in three-dimensional sedimentary basins in recently years. However, the structure and size of the large, realistic, three-dimensional sedimentary basin and the frequency range of analysis are limited by computer memory and performance. Yoshida (2001) showed that the Fast Multipole Method (FMM) can be used to accelerate the iterative solution of boundary integral equations by reducing the memory capacity and computation time, thus its application to the BEM can overcome the restriction. Most previous applications of BEM have assumed a homogeneous medium in the sedimentary basin and used wholespace Green­_s functions for wave propagation between element points. We use halfspace Green­_s functions which include the seismic wavefield interactions at the free surface and need only the boundary elements of the basin interface. So the size of matrix equation to be solved in the Indirect Boundary Element Method (IBEM) can be reduced to about a quarter of that using full space Green­_s functions. Further, we can use the propagator matrix method to compute Green­_s functions for a multilayered structure within the sedimentary basin and simulate a more realistic ground motion. Finally, the reduction in memory requirements and computation time are achieved with the FMM, which makes use of a Taylor series expansion of these Green­_s functions. This involves the computation of second order spatial derivatives of the Green­_s functions, which are derived analytically. We validate the IBEM-FMM by computing the site response in the croissant-shaped model of Sanchez-Sesma and Luzon (1995). We also apply the method to the real sedimentary basin model in Caracas, Venezuela. The basin-generated surface waves can be identified propagating back and forth inside the basin and these also generate surface waves outside the basin.
DE: 7200 SEISMOLOGY
DE: 7290 Computational seismology
SC: Seismology [S]
MN: Fall Meeting 2005