西巩驿—李店断裂晚第四纪活动特征——及对1352年会宁7级地震发震构造的初步探讨  

Late Quaternary activity characteristics of the Xigongyi-Lidian fault:discussion on the seismogenic structure of Huining M 7 earthquake in 1352

作　　者：崔浇 王爱国[1,2] 张波 陆诗铭[1] 冯紫微 CUI Jiao;WANG Aiguo;ZHANG Bo;LU Shiming;FENG Ziwei(Lanzhou Institute of Seismology,CEA,Lanzhou 730000,Gansu,China;Gansu Lanzhou Geophysics National Observation and Research Station,Lanzhou 730000,Gansu,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

出　　处：《地震工程学报》2023年第3期513-522,共10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)。

摘　　要：西巩驿—李店断裂为陇中盆地内部发育的一条活动断裂,断裂活动性的认识对评估陇中盆地内部地震危险性,以及深入理解印度板块与欧亚板块碰撞的远程响应具有重要的科学意义。遥感解译和地震地质调查结果表明:(1)西巩驿—李店断裂位于陇中盆地中部,断裂长度约120 km、走向NWW、倾向NW、倾角75°~80°。(2)断裂活动的分段特征明显,断裂中部位于加里东期花岗岩隆起区,地表出露不明显,据此将断裂划分为东、西两段。(3)西段新活动现象明显,主要表现为线性陡崖、高约几米的陡坎地形、山梁和冲沟水系的左旋位错等;东段地表构造地貌人为改造严重且黄土区滑坡发育,断层断错晚第四纪的剖面出露较少,晚更新世有活动,性质为逆冲兼左旋,浅地表局部表现为视正断。(4)结合14C测年结果分析,初步认为西段存在全新世活动,且活动性质为逆冲兼左旋走滑,全新世以来的垂直滑动速率为0.342 mm/a±,晚更新世晚期以来的左旋滑动速率最大为1.60~1.67 mm/a。(5)西段在晚更新世晚期以来至少发生过两次地震事件,一次发生在(11 808~11 401) a B.P.之前;一次事件发生在(6 291~6 120) a B.P.至(5 309~5 050) a B.P.之间。(6)结合前人研究资料分析认为,西巩驿—李店断裂西段可能为1352年会宁7级地震的发震断裂,为本区NEE向构造应力作用下NWW向断裂左旋逆冲作用发震。As an active fault developed in the Longzhong Basin,understanding the activity of the Xigongyi-Lidian fault is essential for assessing the seismic hazards in the Longzhong Basin and the remote response of the collision between Indian and Eurasian plates.The results of remote sensing interpretation and seismic geological survey show that:(1)the Xigongyi-Lidian fault is located in the central part of Longzhong Basin,with a length of about 120 km,an NWW strike,an NW dip,and a dip angle of 75°-80°.(2)The segmental feature of the fault activity is prominent.The central part of the fault is located in the Caledonian granite uplift area,and the surface is not exposed.On this basis,the fault is divided into east and west.(3)New activity in the western section is evident and mainly manifested as linear cliffs,steep slopes with a height of several meters,and left-lateral offsets in mountain ridges and gully water systems.The eastern section has a serious artificial transformation of surface structure and geomorphology and developed landslides in the loess area.(4)Combined with 14 C dating results,preliminary investigation reveals a possible Holocene activity in the western section,and the nature of the activity is thrust and left-lateral strike-slip.The vertical slip rate since the Holocene is 0.342 mm/a±,and the maximum left-lateral slip rate since the Late Pleistocene is 1.60-1.67 mm/a.(5)Since the Late Pleistocene,at least two seismic events occurred in the western segment:one before(11808-11401)a B.P.and another between(6291-6120)a B.P.and(5309-5050)a B.P.(6)Combined with previous research data,this study concludes that the western section of the Xigongyi-Lidian fault may be the seismogenic fault of the Huining M 7 earthquake in 1352,which was caused by the left-lateral thrust of the NWW-trending fault under the effect of NEE-trending tectonic stress in this area.

关 键 词：西巩驿—李店断裂 陇中盆地 1352年会宁7级地震 发震构造 晚第四纪 

分 类 号：P315[天文地球—地震学]