龙门山前山断裂中段古地震研究  

Research on Paleoearthquakes along the Middle Section of the Front-Range Fault of Longmenshan,China

作　　者：官云彬 徐琳[2] 陈永东[2,3] 秦宇龙 庞仁俊[2] 刘大明[1,2] 李海[2] GUAN Yunbin;XU Lin;CHEN Yongdong;QIN Yulong;PANG Renjun;LIU Darning;LI Hai(College of Earth Science,Chengdu University of Technology,Sichuan Chengdu 610059,China;Northwest Sichuan Geological Team,Sichuan Bureau of Geology and Mineral Resources Exploration and Development,Sichuan Mianyang 621000,China;Institute of Sedimentary Geology,Chengdu University of Technology,Sichuan Chengdu 610059,China;Sichuan Geological Survey,Sichuan Chengdu 610084,China)

机构地区：[1]成都理工大学地球科学学院,四川成都610059 [2]四川省地质矿产勘查开发局川西北地质队,四川绵阳621000 [3]成都理工大学沉积地质研究院,四川成都610059 [4]四川省地质调查院,四川成都610084

出　　处：《四川地震》2023年第1期18-25,共8页Earthquake Research in Sichuan

基　　金：绵阳市活断层普查项目资助(MYZC招(2020)71号)。

摘　　要：“5·12”汶川地震形成了3条地表同震破裂带,前人以此为线索在龙门山中央断裂中段、前山断裂中段以及小鱼洞断裂开展了系列古地震探槽研究,在古地震识别、年代控制、活动特征和大地震原地复发周期等方面取得了较好成果,但前山断裂中段中北部的探槽因古地震遗迹破坏较严重或未保存而效果不太理想,为补充前山断裂中段的古地震探槽研究基础数据,笔者在该断裂中部的汉旺镇群新村、北部的雎水镇月儿门村一带的Ⅱ级河流阶地上开挖了2条探槽,并进行了古地震研究工作。结果显示:(1)“5·12”汶川地震导致的地表垂向位移量在汉旺镇群新村白溪河南西岸为1.4~1.5 m,在雎水镇月儿门村雎水河东岸约0.53~0.6 m;(2)汉旺镇群新村探槽揭示了包括“5·12”汶川地震在内的至少2次大地震事件,且2次事件的垂向位移量相当,而雎水镇月儿门村探槽仅揭示了“5·12”汶川地震事件;(3)根据AMS^(14)C年龄测定结果,汉旺镇群新村探槽记录的前一次古地震事件应发生在2003±38 cal BP之前,与前人在擂鼓、映秀、小鱼洞、白鹿等地探槽记录的前一次古地震为同一事件,结合前人在地貌、古地震探槽方面的研究及历史记录,笔者认为这次古地震事件可能发生于3100 a BP左右。The "5·12" Wenchuan Earthquake produced three coseismic surface rupture zone.Previous researchers carried out a series of paleoseismic trough trenching along the middle section of the Central fault,the middle section of the Front-range fault and the Xiaoyudong fault.These results showed good results in paleoearthquake identification,paleoearthquake era,characteristics of paleoseismicity and recurrence intervals of large earthquakes.However,the trenches along the north-central of the middle section of the Front-range fault is not ideal because the paleoearthquake evidence was damaged or not preserved.In order to supplement the basic data of the palaeoseismic trench research in the middle section of the Front-range fault,we excavated two trenches at the class Ⅱ river terrace near Qunxin Village of Hanwang Town and Yueermen Village of Jushui Town along this fault.The main results are as follows:(1) The vertical displacement caused by the "5·12" Wenchuan Earthquake is about1.4~1.5 m on the south west bank of Baixi River in Qunxin Village of Hanwang Town,and about 0.53~0.6 m on the east bank of Jushui River in Yueermen Village of Jushui Town;(2) The trench in Qunxin Village of Hanwang Town revealed at least two major earthquakes including the 2008 Wenchuan Earthquake.The vertical displacements of the two events were similar,whereas the trench in Yueermen Village of Jushui Town revealed only the "5·12" Wenchuan Earthquake.(3) According to the results of AMS^(14)C dating,the previous paleoearthquake recorded in the trench in Qunxin Village of Hanwang Town occurred before 2 003±38 cal BP,which is consistent with the previous paleoearthquake recorded in Leigu,Yingxiu,Xiaoyudong and Bailu,etc.Based on the previous studies on geomorphology,paleoseismic trench and historical records,we suggest that the paleoearthquake might be occurred around 3 100 a BP.

关 键 词：龙门山 灌县—江油断裂 古地震 探槽 

分 类 号：P316.04[天文地球—地震学]