Numerical modeling analysis of the tectonic deformation of Bayan Har block in the Tibetan Plateau

A series of strong earthquakes have occurred in the Tibetan Plateau since 1997, distributed along the peripheral faults of Bayan Har block. It is necessary to study the overall tectonic deformation of Bayan Har block. With the constraints from GPS observation, the tectonic deformation of the Bayan Har block and its periphery faults was investigated based on an elasto-plastic plane stress finite element model. The results show that the elastic model could not explain the current GPS observation in the Bayan Har block. When East Kunlun fault and Yushu-Xianshuihe fault were in the plastic yield state (with relative large sliding), the calculated velocity field is consistent well with the observation values, suggesting that most of the current shear deformations (strain localizations) were absorbed by these two faults. In addition, if the recurrence intervals of large earthquakes are used to limit the relative yield strength of major faults, the major faults around Bayan Har block entered the plastic yield state in the following order: The Yushu-Xianshuihe faults and the middle segment of East Kunlun faults first entered the yield state in succession. Then, the Margaichaka-RolaKangri faults (Mani segment) and Heishibeihu faults would enter the yield state, and the eastern segment of East Kunlun faults and Longmenshan faults entered the yield state at last. This indicates that the overall movement of Bayan Har block shows sectional and periodical characteristics.