祁连-海原断裂带库仑应力演化及地震危险性

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

祁连—海原断裂带是青藏高原东北缘重要的活动断裂带,调节着青藏高原北东向推挤作用和阿拉善地块的东西向运动。已有地震地质和数值模型结果显示,祁连—海原断裂带目前存在几个强震破裂空段且其上应力积累显著、断层闭锁程度高,2022年1月8日门源MS6.9地震即发生在祁连—海原断裂带西段的断层高闭锁、应力积累显著的破裂空段。为进一步认识祁连—海原断裂带未来的强震危险性,本文收集整理了青藏高原北部的强震破裂模型,并基于分层黏弹性流变模型计算了青藏高原北部1900年以来的强震对祁连—海原断裂带的库仑应力加载。结果显示,祁连—海原断裂带西段的木里—江仓断裂和托莱山断裂以及中段的金强河—老虎山断裂应力增强显著,最大库仑应力加载可达1 MPa以上。显著的强震库仑应力加载、强震破裂空段与已有数值模型给出的高应力积累区域和断层高闭锁区域吻合,这表明祁连—海原断裂带西段的木里—江仓断裂和托莱山断裂以及中段的金强河—老虎山断裂未来地震危险性高,亟需进一步关注。

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 MS6.9 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 seis-mic 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.