昌马盆地内发现活动正断层  

Discovery of an active normal fault in Changma Basin

作　　者：冯紫微 张波 何文贵 王爱国 庞炜[3] 姚赟胜 朱俊文 FENG Ziwei;ZHANG Bo;HE Wengui;WANG Aiguo;PANG Wei;YAO Yunsheng;ZHU Junwen(Lanzhou Institute of Seismology,CEA,Lanzhou 730000,Gansu,China;Gansu Lanzhou Geophysics National Observation and Research Station,Lanzhou 730000,Gansu,China;The Second Monitoring and Application Center,CEA,Xi'an 710054,Shaanxi,China)

机构地区：[1]中国地震局兰州地震研究所,甘肃兰州730000 [2]甘肃兰州地球物理国家野外科学观测研究站,甘肃兰州730000 [3]中国地震局第二监测中心,陕西西安710054

出　　处：《地震工程学报》2023年第3期523-531,共9页China Earthquake Engineering Journal

基　　金：中国地震局地震预测研究所基本科研业务专项(2020IESLZ02);国家自然基金(41602225);中国国家留学基金项目(202004190032);第二次青藏高原综合科学考察研究(2019QZKK0901);甘肃省地震局创新团队项目(2019TD0101)。

摘　　要：昌马盆地为祁连山西端的山间盆地,前人一直关注其周边断裂(如昌马断裂)的构造变形,盆地内部变形则鲜有研究。基于遥感解译和野外考察、探槽开挖、差分GPS和放射性碳(14 C)测年等方法,发现昌马盆地西北部的一条活动断层。断层长约4 km,总体走向NEE,倾向SE,倾角陡立,断层地貌表现为陡坎、复陡坎、断层沟槽等,陡坎高度0~5.6 m,由WS向NE逐渐增大。断层运动性质以正断为主,最新活动时代为全新世,并识别出2期古地震事件:6670~6885 a B.P.和26330~26915 a B.P.。研究结果表明,在青藏高原东北缘向NE方向挤压扩展的背景下,祁连山造山带发生NW-SE向伸展,导致其西端受到SE向拉张作用而形成正断层。The Changma Basin is an intramontane basin located at the western end of the Qilian Mountains.Previous studies focused on the structural deformation of its surrounding faults(such as the Changma fault),but its internal deformation is rarely studied.This paper presents studies on a newly discovered normal fault in the northwestern part of the Changma Basin on the basis of remote image interpretation,field investigation,trench excavation,differential GPS survey,and radioactive carbon(14 C)dating.The fault is approximately 4 km in length,with a general strike of NE and dips NW.Its geomorphology is characterized by scarps,staircase scarps,and fault troughs.The height of the fault scarp is 0-5.6 m,which increases gradually from southwest to northeast.The fault activity is dominated by normal faulting,and its latest activity is determined in Holocene.The results suggest that due to the NW-trending growth of the northeastern margin of the Qinghai-Tibet Plateau,an NW-SE extension occurred in the Qilian Mountains,and the normal fault in the Changma Basin was formed by the SE extension.

关 键 词：昌马盆地 正断层 古地震 祁连山 昌马断裂 

分 类 号：P315.2[天文地球—地震学]