HR: 0800h
AN: S41A-0946    [Abstracts]
TI: Dynamic Source Rupture Simulation of Dipping Faults With a 3D Finite-Difference Method
AU: * Zhang, W
EM: wenbo@egmdpri01.dpri.kyoto-u.ac.jp
AF: Wenbo Zhang, Lab of Strong Motion Seismology Disaster Prevention Research Institute, Kyoto University, Uji, Kyo 611-0011 Japan
AU: Iwata, T
EM: iwata@egmdpri01.dpri.kyoto-u.ac.jp
AF: Wenbo Zhang, Lab of Strong Motion Seismology Disaster Prevention Research Institute, Kyoto University, Uji, Kyo 611-0011 Japan
AB: The finite-difference method (FDM) has been widely used for numerical modeling of seismic source problems, including investigation on the dynamic source processes. Owing to both conceptual and computational constraints of FDM, fault models have largely been limited to the cases that the fault planes are parallel to the FDM grid. However, recent observation and kinematic inversion results discover that more complex fault geometry models, such as bending faults or curved faults, are needed to explain some earthquake phenomena. Thus, we need to develop an approach of FDM to treat a fault planes slanted with respect to the FDM grid. In this study, we propose a method to analyze the dynamic source problems of nonvertical faults, using a 3D FDM with nonuniform grid spacing (Pitarka, 1999). This approach does not require aligning the fault plane to the FDM grid for implementation of FDM. We estimate the shear stress on the nonvertical fault plane from the six stress components obtained in FDM calculation with respect to the force balance condition and the coordination transformation. This method can be used to deal with a more realistically complex fault geometry model. We validate our method by studying two cases of the dynamic source problems which have been analyzed by Madariaga et al. (1998). One is the instantaneous rupture model of a circular fault embedded in a homogeneous elastic medium; another is the spontaneous rupture model of a rectangular fault which starts from a local circular asperity on the fault plane. We analyze the inclined fault models against the space grid coordination for both of the rupture problems and compare our simulations with previous results obtained by Madariaga et al. (1998) using the horizontal fault plane model. Our simulations gave similar results with those of Madariaga et al. (1998). Thus, our method can be used to analyze the dynamic rupture processes of dipping fault models. This implementation was used to compute the dynamic source problems of the 1999 Chi-Chi, Taiwan, earthquake by Zhang et al. (2003, 2004). We found that the rupture process of this event is more complex than that described in the kinematic model. Our dynamic model revealed that for a large earthquake such as the Chi-Chi earthquake, the rupture propagation can be discontinuous, as suggested by some numerical simulations (Das and Aki, 1977; Day, 1982). In this study, we apply the proposed method to analyze the dynamics of the 2003 Tokachi-Oki, Japan, earthquake. The fault model of this earthquake is a dipping fault with a dip angle of 18 degree. We rebuild the dynamic rupture process of this event and simulate the near source ground motions based on the dynamic source model.
UR: http://sms.dpri.kyoto-u.ac.jp/wenbo/
DE: 7260 Theory and modeling
DE: 7209 Earthquake dynamics and mechanics
DE: 7212 Earthquake ground motions and engineering
DE: 7215 Earthquake parameters
SC: Seismology [S]
MN: 2004 AGU Fall Meeting