HR: 0800h
AN: S11A-0281    [Abstracts]
TI: Effects of realistic surface topography on seismic wave propagation: An example from northern Taiwan
AU: * Lee, S
EM: sjlee@earth.sinica.edu.tw
AF: Institute of Earth Science, Academia Sinica, No. 128, Section 2, Academia Road, Nankang, Taipei, 115, Taiwan
AU: Huang, B
EM: hwbs@earth.sinica.edu.tw
AF: Institute of Earth Science, Academia Sinica, No. 128, Section 2, Academia Road, Nankang, Taipei, 115, Taiwan
AU: Tromp, J
EM: jtromp@gps.caltech.edu
AF: Seismological Laboratory, California Institute of Technology, 1200 E. California Blvd., MS 252-21, Pasadena, CA 91125, United States
AB: Surface topography can influence the ground motion when seismic waves propagate along an irregular free surface. In general, topography increases the amplitude of shaking at mountaintops and ridges, whereas valleys usually have reduced ground motions, as is evident from both numerical simulations and from data recorded after real earthquakes. However, recent attention is mainly focused on mountain regions, and the surrounding areas have received less attention. Here we develop a new spectral-element mesh implementation to accommodate realistic topography and the complex Taipei basin, which is in close proximity to the Central Mountain Range in northern Taiwan. Spectral-element simulations demonstrate that high-resolution topography can change PGA values in mountainous areas by 50% compared to a half-space response. We demonstrate that large-scale surface topography affects the propagation of seismic waves. If a shallow earthquake occurs in the I-lan region, the Central Mountain Range will significantly scatter the surface waves, and in turn reduce the amplitude of the ground motion in the Taipei basin. However, as the hypocenter becomes deeper, topography will scatter the body waves, which subsequently propagate as surface waves into the basin. These waves further interact with the basin and the surrounding mountains, which finally results in complex amplification patterns (PGA increase > 50%) in Taipei city. The complex interactions between mountains and nearby areas, especially sedimentary basins, cannot be ignored. Our simulations demonstrate that surface topography should be taken into account for seismic hazard assessment.
DE: 7200 SEISMOLOGY
DE: 7203 Body waves
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7290 Computational seismology
SC: Seismology [S]
MN: 2007 Fall Meeting