2022年门源M_(S)6.9地震前祁连—海原断裂带闭锁程度及地震危险性研究  

Study on the Locking Degree of the Qilian-Haiyuan Fault Zone before the 2022 Menyuan M_(S)6.9 Earthquake and Its Seismic Risk

作　　者：刘雷 朱良玉[1] 季灵运[1] 庄文泉 刘传金 LIU Lei;ZHU Liangyu;JI Lingyun;ZHUANG Wenquan;LIU Chuanjin(The Second Crust Monitoring and Application Center,China Earthquake Administration,Xi an 710054,Shaanxi,China)

机构地区：[1]中国地震局第二监测中心,陕西西安710054

出　　处：《地震研究》2023年第1期88-98,共11页Journal of Seismological Research

基　　金：陕西省自然科学基础研究计划项目(2021JQ-979)资助。

摘　　要：利用2015—2021年GPS速度场,采用负位错程序反演祁连—海原断裂带的闭锁程度及滑动亏损速率,结合断层面小震分布特征研究2022年门源M_(S)6.9地震震前异常特征,综合分析该断裂带各段的地震危险性,并根据跨断层GPS剖面获取断裂带滑动速率,对区域地壳变形特征进行探讨。结果表明:在2022年门源地震前,冷龙岭断裂处于强闭锁状态,并且闭锁深度在15 km,滑动亏损速率也较大,小震分布也相对较少,这些特征与中强地震的发生密切相关。而金强河断裂、冷龙岭断裂西段和托莱山断裂东段现今闭锁程度较高,闭锁深度深,滑动亏损速率大,具有较高的地震危险性。进一步结合小震分布和2022年门源地震前闭锁特征,认为未来需关注托莱山东段的中强地震危险性。祁连—海原断裂带现今走滑速率为3.9~4.3 mm/a,说明该断裂带整体运动一致性较好,挤压速率从西段的2.9 mm/a向东逐渐减小为1 mm/a,说明青藏高原东北缘现今的地壳形变主要以祁连山上的地壳短缩和祁连—海原断裂带上的左旋走滑运动为主。By using GPS velocity during 2015-2021 and the negative dislocation program,we inverted the locking degree and the slip rate deficit of the Qilian-Haiyuan Fault Zone.Referring to the distribution of small earthquakes in the Fault Zone,we studied the seismic anomalies before the 2022 Menyuan M_(S)6.9 Earthquake,and analyzed the seismic risk of each segment of the Fault Zone.The regional crustal deformation was discussed according to the fault slip rate obtained by the across-fault GPS profile.The results showed that before the Menyuan Earthquake,the seismogenic fault,the Lenglongling Fault,was firmly locked;the locking depth was 15 km,and the slip rate deficit was large,and there were a few small earthquakes.These characteristics were closely related to the medium-and strong-earthquake like the Menyuan Earthquake.The Jinqianghe Fault,the Lenglongling Fault and the eastern segment of the Tuolaishan Fault had deep locking depth,high locking degree,high slip rate deficits,and high seismic risk.Referring to the small-earthquake activity and the locking characteristics of the Lenglongling Fault before the Menyuan Earthquake,we conclude that the medium-and strong-earthquakemay occur in the eastern segment of the Tuolaishan Fault in future.In addition,the strike-slip rate of the Qilian-Haiyuan Fault Zone is between 3.9-4.3 mm/a,and the overall movement of the Fault is consistent.The compression rate(2.9 mm/a)in the western segment gradually decreased to 1 mm/a in the eastern segment.Therefore,the present crustal deformation in the northeastern margin of the Tibetan Plateau is mainly illustrated by the shortening of the Crust in the Mt.Qilianshan area and by the left-lateral,strike-slip of the Qilian-Haiyuan Fault Zone.

关 键 词：祁连—海原断裂带 门源M_(S)6.9地震 断层闭锁 地震危险性 地壳变形 

分 类 号：P315.2[天文地球—地震学]