The Evolution of Stress and Strain around the Bayan Har Block in the Tibetan Plateau

Abstract

With the constraint of GPS observation, the tectonic deformation of the Bayan Har block and its periphery faults is investigated based on an elastoplastic plane-stress finite element model. The results show that the elastic model cannot explain the current GPS observation in the Bayan Har block. When East Kunlun fault and Yushu-Xianshuihe fault are under plastic yield state or high strain localization, the calculated velocities fit well with the observation values. It indicates that most of the current shear deformations or strain localizations are absorbed by these two large strike-slip faults. In addition, if the recurrence intervals of large earthquakes are used to limit the relative yield strength of major faults, the order of entering the plastic yield state of the major faults around Bayan Har block is as follows. The first faults to enter the yield state are Yushu-Xianshuihe faults and the middle segment of East Kunlun faults. Then, Margaichaka-RolaKangri faults (Mani segment) and Heishibeihu faults would enter the yield state. The last faults to enter the yield state are the eastern segment of East Kunlun faults and Longmenshan faults, respectively. These results help us to understand the slip properties of faults around the southeastward moving Bayan Har block.

Present-Day Crustal Deformation of the Northwestern Tibetan Plateau Based on InSAR Measurements

“…These block boundaries attract broad attention from Earth scientists because more than a dozen strong earthquakes occurred in the last half century. However, the Heishibeihu Fault (one of four subsidiary faults) determined to be the northwest margin of the Bayan Har block [43][44][45], has been neglected as an interblock subsidiary fault. The strain distributed between the ATF and the four subsidiary faults in our result confirmed that the subsidiary faults accommodate oblique convergence.…”

“…The geometric traces of subsidiary faults converge at the western end of the EKLF in this region. In previous studies, the Heishibeihu Fault (one of four subsidiary faults) was determined to be the northwestern margin of the Bayan Har block [43][44][45], which is considered to be the block with the most active boundaries in China. Compared with other broadly studied faults (ie., EKLF, Ganzi-yushu-Xianshuihe fault and Longmenshan fault) around the Bayan Har block [18,46,47], its northwestern margin faults have not been given the same attention and the relevant references can almost not be retrieved.…”