西藏阿里阿鲁错地堑系的第四纪活动性、最新同震地表破裂及其地震地质意义  

THE QUATERNARY NORMAL FAULTING AND RECENT COSEISMIC SURFACE RUPTURE AND RELATED SEISMOLOGICAL SIGNIFICANCE ALONG THE ARU CO GRABEN SYSTEM IN NORTHERN NGARI,TIBET

作　　者：吴中海[1,2] 白玛多吉 叶强 韩帅 史亚然 尼玛次仁 高扬 WU Zhong-hai;Baima Duoji;YE Qiang;HAN Shuai;SHI Ya-ran;Nima Ciren;GAO Yang(Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;Key Laboratory of Active Tectonics and Geological Safety,Ministry of Natural Resources,Beijing 100081,China;Geothermal and geological brigade,Geology and mineral exploration and Development of Tibet Autonomous Region,Lhasa 850000,China;Institute of Geological Survey of Tibet Autonomous Region,Lhasa 850000,China;Regional Geological Survey Brigade,Geology and mineral exploration and Development of Tibet Autonomous Region,Lhasa 851400,China;School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;School of Earth and Space Sciences,Peking University,Beijing 100871,China)

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]自然资源部活动构造与地质安全重点实验室,北京100081 [3]西藏自治区地质矿产勘查开发局地热地质大队,拉萨850000 [4]西藏自治区地质调查院,拉萨850000 [5]西藏自治区地质矿产勘查开发局区域地质调查大队,拉萨851400 [6]中国地质大学(北京),地球科学与资源学院,北京100083 [7]北京大学,地球与空间科学学院,北京100871

出　　处：《地震地质》2023年第1期67-91,共25页Seismology and Geology

基　　金：国家自然科学基金(41571013);西藏改则县、措勤县1︰5万地质灾害详细调查项目(XZDK2019-50,51);西藏自治区第1次全国自然灾害综合风险普查项目(2022年地震灾害部分)(XZLX-BMC-2022-053);中国地质科学院地质力学研究所基本科研业务项目(所科研56);中国地质调查项目(DD20221644)共同资助。

摘　　要：藏北高原非常薄弱的活断层调查程度和不完整的历史地震资料等,限制了对青藏高原内部活动构造的变形机制及强震活动特征等问题的深入认识。文中通过综合地质、遥感和地震等资料对阿里北部进行详细的活断层解译,重点对阿鲁错地堑系南段昆楚克错地堑西侧边界正断层的第四纪活动性、新发现的最新同震地表破裂及其震级与形成时间等进行了深入分析。研究结果表明,阿里北部第四纪期间以近EW向伸展变形为主,发育了以近SN向正断层和由NW向与NE向走滑断层构成的共轭走滑断层为主的高密度活断层系统。沿昆楚克错地堑西缘主边界正断层新发现的最新同震地表破裂整体沿NNW向雁列展布,总长约400m,最大垂直位移约0.8m,平均垂直位移为0.3~0.4m。结合历史地震记录和经典的“地表破裂位移与震级”统计关系式推断,该破裂应是震源深度为35km的1955年革吉县纳屋错东M_(W)6.5强震事件的结果。综合该地表破裂的发育特点推断,震源深度对地表破裂参数存在显著影响,震源偏深时的地表破裂长度可远小于震源破裂的最大长度,表明在活断层的地震复发模式研究中应注意随机性较强的断层局部破裂行为或小位移破裂事件。The Qinghai-Tibetan plateau,with an average altitude of about 5000m,is one of the most intense regions of intraplate deformation in the globe during the Quaternary.However,the very weak field investigation of active faults and incomplete historical earthquake data in the northern QinghaiTibet Plateau limit the in-depth understanding of the deformation mechanism of active tectonics and the characteristics of related strong earthquakes in the Qinghai-Tibetan plateau.Based on the comprehensive geological,remote sensing,and seismic data,the active faults in northern Ngari are interpreted in detail,and the Quaternary activity of the normal faults along the western boundary of Kunchuke Co graben in the southern section of the Aru Co graben system,the newly discovered coseismic surface ruptures,its magnitude and seismogenic time are analyzed.The newly active fault images show that high-density active fault system dominated by the near east-west extension deformation was developed in the north Ngari.The Quaternary active fault system mainly includes near north-south normal faults and the conjugated strike-slip faults composed of the NW and NE strike-slip faults.The density of the normal faults is significantly higher than that of the strike-slip faults in the region.Based on the comprehensive analysis of the Aruko graben system and the latest co-seismic surface rupture along the western boundary of Kunchuke Co Graben.We present two main conclusions.1)The Aru Co graben system,with a total length of 210 to 220km,is one of the largest extensional fault depression structures in northern Ngari.The graben system contains four secondary graben and half-graben distributed in left-step echelon distribution from south to north and shows obvious segmented activity characteristics.Meima Co-Aru Co graben is the most intense extensional deformation section along the Aru Co graben system during the Quaternary period.The left echelon pattern of the secondary graben in the graben system indicates that there is a right-lateral shear defor

关 键 词：青藏高原 近EW向伸展变形 正断层 昆楚克错同震地表破裂 阿鲁冰崩 

分 类 号：P315.2[天文地球—地震学]