2001年昆仑山地震同震-震后效应与2021年玛多地震关系探讨  

Coseismic and postseismic deformation of the 2001 M_(W)7.8 Kunlun Mountain earthquake and its loading effect on the 2021 M_(W)7.3 Madoi earthquake

作　　者：屈春燕[1] 赵德政 单新建[1] 岳冲 陈晗 吴东霖 刘恋 张国宏[1] QU ChunYan;ZHAO DeZheng;SHAN XinJian;YUE Chong;CHEN Han;WU DongLin;LIU Lian;ZHANG GuoHong(State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China)

机构地区：[1]中国地震局地质研究所地震动力学国家重点实验室,北京100029

出　　处：《地球物理学报》2023年第7期2741-2756,共16页Chinese Journal of Geophysics

基　　金：地震动力学国家重点实验室课题(LED2019A02);中国地震局地质研究所基本科研业务费专项(IGCEA2104,IGCEA1809);自然科学基金(41872229)联合资助。

摘　　要：位于青藏高原中北部的巴颜喀拉地块是我国西部近年来的主体地震活动区,一系列M_(W)7.0以上强震均发生在该次级块体周边,而其北边界东昆仑断裂带是一条长达2000 km、规模最大、活动性最强的深大断裂带.2001年在东昆仑断裂带中段发生了M_(W)7.8昆仑山地震,2021年5月在其震中东南部大约450 km处巴颜喀拉块体内部一次级断裂上发生了M_(W)7.3玛多地震.玛多地震对人们以往认为强震更可能发生在巴颜喀拉块体边界断裂上的认识提出挑战,但是也为研究巴颜喀拉块体边界断裂与块体内部次级断裂活动关系、地震触发关系带来机遇.本文利用前期基于2001年昆仑山地震后积累的大量InSAR数据获得的震后大范围形变场时空演化图像和库仑应力变化模型,探讨昆仑山地震与玛多地震的关系.InSAR震后观测结果显示:昆仑山地震后沿东昆仑断裂带出现了长达500 km的大范围南北不对称震后形变场,其中南盘形变宽度和量级均明显大于北盘,南盘形变宽度达到250 km,断层近场相对平均形变速率达到>20 mm·a^(-1),而且南盘向南衰减梯度小,整体衰减缓慢,意味着震后形变对巴颜喀拉块体形成持续东向加载作用,并将分摊到块体内部的一系列次级断裂上,应力加载增加次级断层的地震危险性.2015—2020年InSAR震间应变率场则显示次级断裂——昆仑山口—江错断裂呈高剪切应变率特征.本文计算了昆仑山地震同震破裂和震后形变引起的玛多震区多条SE向次级断裂的累积库仑应力变化,结果显示昆仑山地震同震和震后形变对玛多地震发震断裂(昆仑山口—江错断裂)形成了一定的应力加载.本文认为昆仑山地震同震和长时间尺度震后形变加速了巴颜喀拉块体的东向运动,而断层本身运动学性质和区域应力扰动共同影响了玛多地震的发生.The Bayan Har block in the north-central Tibetan Plateau has been the main seismic region in west China in recent years,and a series of major earthquakes with M_(W)>7.0 have occurred around this block.Its northern boundary,the East Kunlun fault,is an active large-scale fault zone with a total length of~2000 km.The 2001 M_(W)7.8 Kunlun Mountain(Hoh Xil)earthquake occurred in the middle segment of the East Kunlun fault(or Kunlun fault),and the M_(W)7.3 Madoi earthquake occurred on a secondary fault inside the Bayan Har block,~450 km southeast of the Kunlun Mountain earthquake.The Madoi earthquake challenges the previous long-held view that strong earthquakes are more likely to occur on the boundary faults of the Bayan Har block.This earthquake also provides an opportunity to study the relationship among the boundary faults and secondary faults,and earthquakes triggering within the block.This paper explores the potential relationship between the Kunlun Mountain earthquake and the Madoi earthquake using postseismic InSAR observations and the Coulomb stress change,which are obtained from a large amount of SAR data acquired after the Kunlun Mountain earthquake.The InSAR postseismic deformation shows a widespread asymmetric pattern along the rupture zone,and the deformation width and magnitude of the southern part are significantly larger than the northern one.The deformation width of the southern part reaches 250 km,and the near-field deformation rate reaches>20 mm·a^(-1).The decay of displacement rate on the southern part is insignificant,implying that the postseismic deformation forms a enduring eastward loading effect on the Bayan Har block,and will be partitioned into a series of secondary faults inside the block.The stress loading increases the seismic potential of the secondary faults.The interseismic strain map during 2015—2020 shows a high strain rate zone along the secondary fault,the Kunlun Mountain Pass—Jiangcuo fault.We calculate the cumulative Coulomb stress change caused by the coseismic rupture and

关 键 词：巴颜喀拉块体 东昆仑断裂 昆仑山地震 玛多地震 震后效应 

分 类 号：P541[天文地球—构造地质学] P223[天文地球—地质学]