Contemporary kinematics in the eastern Tibetan Plateau: Insights from 3D geomechanical modeling

Abstract

The slip rates on the faults in the eastern Tibetan Plateau play an important role in understanding the plateau's evolution and assessing its seismic hazard. In order to obtain a quantitative picture of the continuous slip rate along and slip partitioning between the faults, we establish a comprehensive 3D geomechanical-numerical model of the eastern Tibetan Plateau. Our results show that the NW-SE-trending faults usually slip faster than the faults striking in NE-SW direction. A substantial variation of the slip rate gradient along the Xianshuihe fault is revealed. The southeastern segment (Moxi fault) has a higher slip rate gradient than the northwestern segment, which is inferred to be caused by a clockwise rotation of the strike of the Xianshuihe fault from NW-SE to NNW-SSE near Kangding. This rotation combined with the accommodated southeastward movement of the Chuan-Dian Block further promotes normal faulting on the southwestern-most section of the Longmen Shan fault. According to the relatively higher slip rate of the Huya fault and the geometric distortion of the Yingxiu-Beichuan fault, we suggest that the Huya fault may have penetrated into the Longmen Shan fault zone and partially transmitted deformation of the Minshan Uplift into the sedimentary cover of the Sichuan basin. Based on the analysis of contemporary kinematics in the eastern Tibetan Plateau, we suggest that the Moxi fault has a high seismic hazard with the potential of an Ms7.4 earthquake, while the northeastern segment and the southwestern-most section of the Longmen Shan fault zone tend to produce more frequent but lower magnitude earthquakes.