Synthetic Seismicity Model for the Xianshuihe Fault, Southwestern China

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(1)Tectonic Model. We investigated deformation pattern of China using GPS data. Assuming that China consists of several rigid blocks, we determined displacement rates, slip deficit on faults, and internal deformation of the blocks. The results show that the displacement rate of the Sichuan-Yunnan block, which is caused by the collision of India, is 7.0 to 9.5 mm/yr, consistent with the geologically estimated value of 9 mm/yr. The slip deficit along the Xianshuihe fault is significantly smaller than the relative displacement rate between the two rigid blocks, indicating that the fault is virtually locked. (2)Laboratory Experiment. We measured acoustic emission (AE) during brittle deformation process of rock samples with preexisting joints under tri-axial compression. For rock samples without joints, the hypocenters of AEs are scattered and the fractal dimension of the hypocenter distribution is low when the applied compressional stress is low. On the other, in the case of rock samples w … More ith joints, AEs are concentrated along the joints under low compressional stress. AE clusters are generated near joint bends. (3)Numerical Simulation of Seismicity along the Xianshuihe Fault. We develop a synthetic seismicity model, assuming that the frictional stress of the fault follows a laboratory-derived rate and state-dependent friction law and using the long-term average slip rate along the fault estimated from geologically and geodetic observations. By selecting appropriate model parameters, we can simulate recurrence of active periods of fault motion with a recurrence interval of a few hundred years, being consistent with historically recorded seismicity. Rupture is arrested at regions of fault bend or branch or regions with velocity-strengthening frictional property. The arrested rupture is often reactivated after several years. This is because aseismic sliding propagates slowly in the velocity-strengthening regions. This explains migration of seismic activity along the fault. Less