2022年1月8日M_(S)6.9青海门源地震震前三维地壳变形与应变分配  

Three-dimensional crustal deformation and strain partitioning before the MS6.9 Qinghai Menyuan earthquake on January 8, 2022

作　　者：李长军[1] 郝明[1,2] 李煜航 宋尚武[1] LI ZhangJun;HAO Ming;LI YuHang;SONG ShangWu(The Second Monitoring and Application Center,Xi'an 710054,China;Southern Laboratory of Ocean Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai Guangdong 519080,China)

机构地区：[1]中国地震局第二监测中心,西安710054 [2]南方海洋科学与工程广东省实验室(珠海),广东珠海519080

出　　处：《地球物理学报》2023年第2期576-588,共13页Chinese Journal of Geophysics

基　　金：国家重点研发计划(2017YFC1500102);国家自然基金项目(42002234,41874117,41874017);陕西省自然科学基础研究计划(2022JQ-235)联合资助。

摘　　要：2022年01月08日在祁连山断裂带中东段的青海门源县发生了M_(S)6.9强震,然而,迄今为止对于该地区的三维地壳变形特征和强震孕育背景鲜有研究.本文基于高精度的GPS和水准等大地测量资料,厘定了该区域主要活动断裂的滑动速率,并分析了此次地震之前的三维地壳变形特征和强震孕育背景.研究结果表明,(1)祁连山断裂带中东段地壳变形呈现出较强的左旋剪切和缩短变形,且地壳缩短主要以垂直隆升的形式实现;(2)托莱山断裂的走滑、缩短和垂直速率分别为2.5±0.3 mm·a^(-1)、1.3±0.4 mm·a^(-1)和1.2±0.6 mm·a^(-1),高于其北侧的民乐-大马营断裂的1.1±0.3 mm·a^(-1)、0.8±0.3 mm·a^(-1)和0.5±0.5 mm·a^(-1),冷龙岭断裂的走滑和缩短速率分别为3.1±0.7 mm·a^(-1)和3.0±0.6 mm·a^(-1),结合应变率场,表明该区域地壳变形满足连续-弥散变形模式;(3)此次门源地震震前剪应变和压性面应变明显积累,其中部分压性面应变被2016 M_(S)6.4地震所释放,而在托莱山和冷龙岭断裂以南地区垂直变形并不显著,震前应变持续增加.此外,GPS速度剖面揭示出托莱山断裂存在明显的震间闭锁,其闭锁深度为15.0±7.8 km,表明其具有发生强震的背景.The MS6.9 Qinghai Menyuan earthquake, occurred on Jan. 8, 2022, was located in the central to eastern segment of the Qilianshan fault zone. However, the 3D crustal deformation and seismic potential in this region were poorly studied to date. We here determine the fault slip rates and analyze 3D crustal deformation and seismic potential before this event based on the accurate GPS and leveling observations. The results show that, first, crustal deformation in this area is mainly featured by strong shear and contraction, with the latter accommodated by crustal uplift. Second, sinistral, contraction and vertical rates of the Tuolaishan fault are 2.5±0.3 mm·a^(-1), 1.3±0.4 mm·a^(-1)and 1.2±0.6 mm·a^(-1), which are larger than those of Minle-Damaying fault of 1.1±0.3 mm·a^(-1), 0.8±0.3 mm·a^(-1), and 0.5±0.5 mm·a^(-1), respectively. The sinistral and contraction rates of the Lenglongling fault are 3.1±0.7 mm·a^(-1)and 3.0±0.6 mm·a^(-1). Combined with strain rate field, we suggest that upper crust in this region is characterized by distributed deformation. Third, shear and compressional strain in the hypocentral region accumulated significantly before this earthquake, in which part of compressional strain was released by the 2016 MS6.4 Menyuan earthquake. While negligible vertical deformation in the south of the Tuolaishan and Lenglongling faults indicate the increase of strain rate. Additionally, GPS velocity profile presents clear interseismic locking along the Tuolaishan fault with a locking depth of 15.0±7.8 km, which indicates a high seismic potential.

关 键 词：2022年M_(S)6.9门源地震 三维地壳变形 应变分配 GPS和水准观测 

分 类 号：P228[天文地球—大地测量学与测量工程] P315[天文地球—测绘科学与技术]