三危山断裂敦煌段古地震活动特征  

PALEOEARTHQUAKE CHARACTERISTICS IN DUNHUANG SEGMENT OF THE SANWEISHAN FAULT

作　　者：刘兴旺 袁道阳 姚赟胜 邹小波 LIU Xing-wan;YUAN Dao-yang;YAO Yun-sheng;ZOU Xiao-bo(Gansu Lanzhou Geophysics National Observation and Research Station,Lanzhou 730000,China;Lanzhou Institute of Geotechnique and Earthquake,China Earthquake Administration,Lanzhou 730000,China;School of Earth Sciences,Lanzhou University,Lanzhou 730000,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,兰州730000 [2]中国地震局兰州岩土地震研究所,兰州730000 [3]兰州大学,地质科学与矿产资源学院,兰州730000

出　　处：《地震地质》2021年第6期1398-1411,共14页Seismology and Geology

基　　金：中国地震局地震预测研究所基本科研业务专项(2019IESLZ03,2019IESLZ01);第2次青藏高原综合科学考察研究(2019QZKK0901)共同资助。

摘　　要：三危山断裂位于青藏高原北缘NW向扩展的前缘位置,其最新地震活动反映了高原北部地区的构造变形特征。文中通过遥感影像解译、野外实地调查、古地震探槽及光释光年代样品测试,对三危山断裂敦煌段的古地震活动特征开展了研究。结果表明,断裂晚更新世以来发生过2次古地震事件,事件E1发生的年代约为距今(35.1±3.7)~(36.7±4.1)ka;事件E2发生的年代约为距今(76.5±8.8)~(76.7±8.3)ka。三危山断裂晚更新世以来的垂直滑动速率为(0.03±0.01)mm/a,相应的缩短速率为(0.09±0.01)mm/a。综合前人的研究结果,认为三危山断裂的地震活动具有分段性特征,中段、东段可能具有独立破裂的能力,也存在与敦煌段发生级联破裂的特征,复发间隔约为40ka,根据经验公式估算三危山断裂可能发生的震级范围为M_(W)7.1~7.5。The Sanweishan Fault is located in the front of the northwest growth of the northern margin of Tibetan plateau,a branch fault of the Altyn Tagh Fault which extends to the northwest.The latest seismic activity of the Sanweishan Fault reflects the tectonic deformation characteristics of the northern plateau.Meanwhile,it is of great significance for the seismic risk assessment of Dunhuang and its adjacent areas to understand the characteristics of earthquake recurrence.The Sanweishan Fault runs along the western piedmont of the Sanwei Shan,with a total length of 175km.The fault is characterized by left-lateral strike-slip and reverse faulting,with local normal fault features.Based on the geometry,the fault can be divided into three segments,i.e.the Shuangta-Shigongkouzi,the Shigongkouzi-Shugouzi and the Shugouzi-Xishuigou segment from east to west.Previous studies about the paleoearthquakes on the Sanweishan Fault mainly focus on the middle and east segments of the fault,while the west segment of the fault has been less studied.Meanwhile,the available research does not involve the recurrence characteristics and possible magnitude of the paleoearthquakes.Based on high-resolution satellite images,we found that the main fault has grown toward the basin and formed fault scarps in the western segment of the Sanweishan Fault.We have carried out a detailed study on these fault scarps.Based on trench excavation and chronological study on the latest fault scarps,this paper determines the sequence of the paleoseismic events on the fault and discusses the recurrence characteristics and possible magnitude of earthquake for the Sanweishan Fault.In the western segment of the fault,through satellite image interpretation and field investigation,we found new fault scarps distributed on the alluvial fan in front of the mountain near Gedajing.We called it Dunhuang segment of the Sanweishan Fault.The activity characteristics of the fault scarps may reflect the latest seismic events in the western part of the Sanweishan Fault.Different

关 键 词：三危山断裂 晚更新世 古地震 敦煌 

分 类 号：P315.2[天文地球—地震学]