HR: 1330h
AN: S52A-0116    [PDF]
TI: Dynamic Rupture Process of the 1999 Chi-Chi Earthquake
AU: * Zhang, W
EM: wenbo@egmdpri01.dpri.kyoto-u.ac.jp
AF: Wenbo Zhang, Disaster Prevention Research Institute, Kyoto University, Kyoto, Japan, Uji, Kyo 611-0011 Japan
AU: Iwata, T
EM: iwata@egmdpri01.dpri.kyoto-u.ac.jp
AF: Wenbo Zhang, Disaster Prevention Research Institute, Kyoto University, Kyoto, Japan, Uji, Kyo 611-0011 Japan
AU: Irikura, K
EM: irikura@egmdpri01.dpri.kyoto-u.ac.jp
AF: Wenbo Zhang, Disaster Prevention Research Institute, Kyoto University, Kyoto, Japan, Uji, Kyo 611-0011 Japan
AU: Pitarka, A
EM: Arben_Pitarka@urscorp.com
AF: Arben Pitarka, URS Greiner Woodward Clyde, USA, Pasadena, CA 91101 United States
AU: Sekiguchi, H
EM: haruko.sekiguchi@aist.go.jp
AF: Haruko Sekiguchi, AFRC, Geological Survey of Japan, Tsukuba, 305-8567 Japan
AB: Earthquake source dynamics provides key elements for the prediction of strong ground motion and for understanding the physics of earthquake processes. This research investigates the characteristics of dynamic source rupture process of the 1999 Chi-Chi earthquake by using a 3D finite difference method with variable grid spacing. A new algorithm is proposed to deal with a non-planar fault model. This approach does not require aligning the fault plane to the finite-difference grid for implementation of FDM and provide a method to deal with a more realistically irregular geometry fault model. We apply this approach to the 1999 Chi-Chi earthquake with a curved fault surface and rebuild the dynamic source rupture process for this larger earthquake. Our results show that for the Chi-Chi earthquake, the behaviors of the most of the subfaults followed a slip-weakening friction law during rupture. And the distributions of the dynamic source parameters estimated from the kinematic results are quite heterogeneous. For the dynamic rupture process, this study reveals the rupture propagation jumping phenomenon which is difficult to be simulated in kinematic modeling. That is when the propagation front encountered a zone with a high strength excess, the rupture would pause to accumulate more energy to break it. Meanwhile, if there are low strength excess zones around the barrier, the propagation front would jump over the barrier to break the low strength excess zones and leave the high strength barrier unbroken. Such phenomenon of the high strength excess barriers intend to delay the propagation front can be seen clearly in the dynamic model. Using a thick fault zone model, the dynamic model discovers that the slip on the hanging-wall side is larger than that on the food-wall side and the northern parts have the longer source duration that the southern parts and these northern parts have an extreme large slip. Based on the dynamic source rupture model, the strong ground motions near the fault surface breaks are simulated in frequency range of 0.05 to 0.5 Hz. In general, the synthetic velocity waveforms agree well with the observed records for most stations. The dynamic source model successfully simulates the distinctive velocity pulse for the stations in the forward rupture direction. Also our dynamic source model successfully reproduced the waveforms as well as the distinctive velocity pulses for the station nearby or on the fault surface breaks. These results demonstrate that our dynamic source model can reproduce the main features of long period ground motions; hence, lead us to a better understanding on the source rupture process of the Chi-Chi earthquake.
DE: 7200 SEISMOLOGY
DE: 7209 Earthquake dynamics and mechanics
DE: 7212 Earthquake ground motions and engineering
DE: 7215 Earthquake parameters
DE: 7260 Theory and modeling
SC: Seismology [S]
MN: 2003 Fall Meeting