HR: 16:45h
AN: S42J-03 INVITED     [PDF]
TI: Spectral-element simulations of seismic wave propagation
AU: * Tromp, J
EM: jtromp@gps.caltech.edu
AF: Seismological Laboratory, California Institute of Technology, Pasadena, CA 91125
AU: Komatitsch, D
EM: komatits@gps.caltech.edu
AF: Seismological Laboratory, California Institute of Technology, Pasadena, CA 91125
AU: Tsuboi, S
EM: tsuboi@jamstec.go.jp
AF: Institute for Frontier Research on Earth Evolution, Japan Marine Science & Techmology Center, Yokohama, 236-0001 Japan
AB: We use a spectral-element method to simulate seismic wave propagation. The method is based upon a weak formulation of the equations of motion and combines the flexibility of a finite-element method with the accuracy of a global pseudospectral method. The finite-element mesh honors all first- and second-order discontinuities in the model. To maintain a relatively constant resolution throughout the model in terms of the number of grid points per wavelength, the size of the elements is increased with depth in a conforming fashion, thus retaining a diagonal mass matrix. In the solid portions of the model we solve the wave equation in terms of displacement, whereas in the fluid regions we use a formulation based upon a scalar potential. The domains are matched by honoring the continuity of traction and the normal component of displacement. The effects of attenuation, anisotropy, self-gravitation, rotation, and the oceans are incorporated. The method is implemented on parallel computers using a message-passing technique. We benchmark spectral-element synthetic seismograms against normal-mode and discrete wavenumber synthetics for laterally homogeneous models. The technique is used to assess strong ground motions in the Los Angeles basin, to investigate effects of full anisotropy on body and surface waves, to perform 3D centroid-moment tensor inversions, and to assess the quality of 3D mantle models. The basin simulations are performed on a Linux PC cluster, and some of the global simulations are performed on the Earth Simulator, the world's largest and fastest computer. On the Earth Simulator we use a very large mesh with 5.5~billion grid points (14.6~billion degrees of freedom) that requires 2.5~terabytes of memory. The vectorization ratio is 99.3%, and we reach a performance of 5~teraflops (30% of the peak performance) on 38% of the machine (243 out of 640 nodes, for a total of 1944 processors). The very high resolution of the mesh facilitates fully 3D calculations at seismic periods of 5~seconds.
DE: 7203 Body wave propagation
DE: 7207 Core and mantle
DE: 7260 Theory and modeling
SC: Seismology [S]
MN: 2003 Fall Meeting