Global finite elemtent simulation of short period seismic waves

Research Project

Project/Area Number	12640406
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	固体地球物理学
Research Institution	Tokyo Institute of Technology
Principal Investigator	OKAMOTO Taro Tokyo Inst.Tech, Dept.Earth Planet.Sci., Research Associate, 大学院・理工学研究科, 助手 (40270920)
Project Period (FY)	2000 – 2001
Project Status	Completed (Fiscal Year 2001)
Budget Amount *help	¥3,600,000 (Direct Cost: ¥3,600,000) Fiscal Year 2001: ¥1,000,000 (Direct Cost: ¥1,000,000) Fiscal Year 2000: ¥2,600,000 (Direct Cost: ¥2,600,000)
Keywords	finite element method / seismic waves / seismo-acoustic scattering / fluid-solid interface / 不規則地形 / 表面波
Research Abstract	(1)We developed a 2D finite element method for the simulation of seismic waves in heterogeneous media. We use a hybrid, seismo-acoustic approach so that we can simulate the scttering of the seismic waves (in elastic media) and the sound (pressure) wave (in fluid media), as the seismo-acoustic scattering is very important for seismic waves travel through the oceanic regions or through the deep core-mantle boundary. In order to do that, we discrimate between solid elements and fluid elements so that the boundary nodes have two values (displacement and pressure), and the solid-fluid boundary conditions are exactly satisfied right at the boundary of elements. We also incorporated the anelastic attenuation by complex-valued elastic moduli (this is possible because we selected the frequency domain formulation instead of the time domain formulation). We evaluated the various aspects of our method (seimo-acoustic scattering, feasibility for irregular shapes and interfaces, and anelastic attenuation). (2)We developed a parallel, distributed computation program of the above finite element method. This is required because the very large complex-valued sparse linear system must be solved to model the global wave field. Our approach is to distribute the elements of the stiffness matrix and vectors among processors and to apply a distributed GP-BiCG algorithm to solve the system iteratively. We showed that we are able to solve a problem of about 3,000,000 degrees of freedom in a relatively short time (about 1000s) with a small PC cluster of 10 processors. We plan to apply these method to model the far-field body waves such as Pdiff.