Coulomb stress evolution and seismic hazards along the Qilian-Haiyuan fault zone

The Qilian-Haiyuan fault zone （QHF） is one of the most active faults in the northeastern margin of the Tibetan Plateau, which regulates the northeastward spreading of the Tibetan Plateau and the eastward movement of Alxa block. Previous studies indicate that there are several seismic gaps with high fault locking and high stress accumulation rate along the QHF. The Menyuan M_S6.9 earthquake on January 8, 2022 ruptured the western segment of the QHF with high fault locking and high stress accumulation. To further understanding the seismic hazards of the QHF, we investigated the Coulomb stress evolution along the QHF based on a layered viscoelastic lithosphere model and the updated coseismic rupture models of the strong earthquakes in the northern Tibetan Plateau since 1900 based on the geological investigation. Our results show there are two Coulomb stress loading segments along the QHF, they are the Muli-Jiangcang fault and Tuolaishan fault in the west, and the Jinqianghe-Laohushan fault in central of the QHF, with the maximum Coulomb stress loading as large as more than 1 MPa. Moreover, the two segments with high Coulomb stress loading are also consistent with the seismic gap with high fault locking and high interseismic stress accumulation rate, manifesting that the two segments are at high seismic risk that deserves more attention in the further researches.