HR: 10:35h
AN: S52A-02    [Abstracts]
TI: Mesh Creation and Strong Ground Motion Simulations in the Taipei Basin based upon the Spectral-Element Method
AU: * Lee, S
EM: sjlee@earth.sinica.edu.tw
AF: Institute of Earth Science, Academia Sinica, No. 128, Section 2, Academia Road, Nankang, Taipei, Taiwan, Taipei, 115
AU: Tromp, J
EM: jtromp@gps.caltech.edu
AF: California Instutute of Technology, Seismological Laboratory, 1200 E. California Blvd., MS 252-21, Pasadena, California, 91125-2100
AU: Chen, H
EM: hwchen@earth.ncu.edu.tw
AF: Institute of Geophysics, National Central University, No.300, Jhongda Rd., Jhongli City, Taoyuan County, Taiwan, Jhongli, 32001
AU: Huang, B
EM: hwbs@earth.sinica.edu.tw
AF: Institute of Earth Science, Academia Sinica, No. 128, Section 2, Academia Road, Nankang, Taipei, Taiwan, Taipei, 115
AB: Strong motion site responses as well as scenario earthquake studies are important tasks for earthquake hazard analysis within the Taipei metropolitan region. Taking the advantage of spectral-element method (SEM), the surface topography and subsurface structures, such as sedimentary basins, the Moho and the subducting plate, can be effectively incorporated in an SEM mesh. While for steep topography or a highly complex subsurface the mesh is seriously distorted, potentially leading to a numerically unstable problem. Here we show new techniques to incorporate topography and complex subsurface structures with successful benchmarks for the Taipei Basin. First, an additional doubling layer with variable grid size along depth axis is needed to have finer mesh configuration near the surface in order to save memory and computing time. A smoothed buffer map is then applied to reduce mesh distortion induced by steep surface topography. Finally, we adjusted the nodes of the basin meshes to coincide with the complex geometry of the basement boundary in the Taipei Basin. With this high resolution model, seismic responses from SEM based 3D simulation show that the ground motion within the Taipei Basin is strongly depends on the source frequency and basin geometry. The amplification of ground motion is mainly controlled by the depth of the basin. The lateral variations of S wave velocity also play an important role in modeling site amplification phenomena. Our results indicate that a high resolution topography mesh that follows most of the DTM data can be achieved. Large lateral variations in subsurface boundaries can also be careful defined by adjusting the nodes of the affected elements. With these developments, the spectral-element mesh readily deals with the complex subsurface in the Taipei metropolitan region, such as steep topography, complex basin structure, Moho and even the subducting plate beneath northern Taiwan. It will be straightforward to apply these techniques to build a model for all of Taiwan or other to study other regions with complex subsurface structures.
DE: 0500 COMPUTATIONAL GEOPHYSICS (3200, 3252, 7833)
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7290 Computational seismology
DE: 8180 Tomography (6982, 7270)
SC: Seismology [S]
MN: Fall Meeting 2005