2021年阿克塞M_(S)5.5地震区形变特征及发震机制研究  

Tectonic deformation and seismic mechanism of the 2021 Aksai M_(S)5.5 earthquake

作　　者：邹小波 李兴坚 邵延秀 袁道阳[5] 邱江涛 尹欣欣[1,2] 寇俊阳 ZOU Xiaobo;LI Xingjian;SHAO Yanxiu;YUAN Daoyang;QIU Jiangtao;YIN Xinxin;KOU Junyang(Gansu Lanzhou Geophysics National Observation and Research Station,Lanzhou 730000,Gansu,China;Gansu Earthquake Agency,Lanzhou 730000,Gansu,China;School of Earth System Science,Tianjin University,Tianjin 300072,China;State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;School of Earth Sciences,Lanzhou University,Lanzhou 730000,Gansu,China;The Second Monitoring and Application Center,CEA,Xi’an 710054,Shaanxi,China)

机构地区：[1]甘肃兰州地球物理国家野外科学观测研究站,甘肃兰州730000 [2]甘肃省地震局,甘肃兰州730000 [3]天津大学地球系统科学学院,天津300072 [4]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 [5]兰州大学地质科学与矿产资源学院,甘肃兰州730000 [6]中国地震局第二监测中心,陕西西安710054

出　　处：《地质力学学报》2024年第6期978-990,共13页Journal of Geomechanics

基　　金：第二次青藏高原综合科学考察研究项目(2019QZKK0901);甘肃省青年科技基金计划项目(22JR11RA088);地震动力学国家重点实验室项目(LED2023B04);甘肃省地震局地震科技发展基金项目(2021Y12,2019Y05)。

摘　　要：2021年8月26日甘肃阿克塞党河南山地区发生了M_(S)5.5地震,震中位于阿尔金走滑断裂与祁连山西段挤压逆冲断裂的构造转换区。明确此次地震的形变特征及发震机制,有助于认识边界走滑断裂与逆冲断裂系之间应变分配和构造转换的大陆动力学问题,同时对祁连山西段的地震危险性评价也具有重要意义。利用远近场地震波形联合反演(the generalized Cut-and-Paste joint,gCAPjoint)此次地震的震源机制解。通过对地震序列走时信息以及地震前后的合成孔径雷达(Synthetic Aperture Radar,SAR)影像数据进行处理,得到了此次地震序列的精确空间位置和同震形变场。结合震中附近活动构造和构造地貌实地调查,认为此次地震的发震构造为党河南山南缘断裂,断裂活动性质为逆冲型。该断裂走向为315°、倾角为41°、滑动角为81°,震源矩心深度为6.9 km。随着青藏高原向北东向的挤压扩展,柴达木地块北部地震活动显著增强,未来阿尔金断裂东段和祁连山西段的地震危险性应重点关注。[Objective]On August 26,2021,an M_(s)5.5 earthquake occurred in Aksai,Gansu Province.The epicenter is located along the southern piedmont of the Danghe Nan Shan.This event garnered significant attention because of its deformation characteristics and seismogenic mechanisms.Existing studies have mainly focused on emergency response and seismic activity analyses;however,there is a lack of research on tectonic deformation and seismic mechanisms.This study aimed to fill this gap by analyzing the deformation characteristics of the earthquake zone and revealing its seismogenic mechanism.[Methods]This study employed seismological methods combined with interferometric synthetic aperture radar(InSAR)technology to investigate the tectonic deformation and seismic mechanism of the 2021 Aksai M_(s)5.5 earthquake.Combining focal mechanism solutions,precise earthquake locations,and InSAR results,the seismogenic fault and its geometric and kinematic parameters were determined and validated through geological field surveys.[Results]This study applied joint inversion with both local and teleseismic waveforms(the generalized cut-and-paste joint,gCAPjoint)to source parameters.The fault solutions strike 315°,dip 41°,rake 81°,depth 6.9 km.We relocated the Aksai earthquake and its aftershocks using the hypoinverse and double-difference method(HypoDD),and accurate locations of 88 earthquakes were obtained.The 2021 M_(s)5.5 earthquake sequence in Aksai is distributed near the southern Danghe Nan Shan Fault,with a fault dip toward the NE.The co-seismic deformation field indicated by InSAR matched the macro-epicenter with the precise location results,confirming the reliability of the precise location.Both the ascending and descending orbit surface deformation fields showed uplift near the epicenter with similar magnitudes and signs in the line-of-sight direction,indicating that the earthquake rupture was mainly thrusting.Fault scarps near the epicenter along the southern piedmont of the Danghe Nan Shan were recognized in the field and sa

关 键 词：甘肃阿克塞M_(S)5.5地震 震源机制解 发震构造 党河南山南缘断裂 

分 类 号：P315.2[天文地球—地震学]