【摘要】 龙门山前山断裂大地震是原地重复发生的吗?针对这一问题,对前山断裂的同震地表形变带进行了追踪,并选择5.12汶川地震区九龙、白鹿以及汉旺等3个地点开展了古地震探槽研究工作。调查结果是:前山断裂5.12地震地表形变带基本沿1:200000地质图上先存基岩断裂发育,但仅限于通济-安昌以南段;白鹿-八角一带同震地表形变带继承先存断层陡坎或断层沟谷发育;偏离先存断裂而被一些学者视为断裂全新世活动重要证据的永安附近T1阶地上线性陡坎实为废弃河岸;白鹿、汉旺探槽剖面揭示这两个地点5.12汶川地震之前至少有过一次古地震事件。这些研究结果表明前山断裂大地震是沿晚第四纪活动断裂原地重复发生的,此次地震是沿先存活动断裂又一次发生的大地震事件,为大地震原地复发模型提供了一个新的震例支持。在沿该断裂周边进行规划建设时应当合理避让。更多还原

【Abstract】 Had severe earthquakes occurred repeatedly at the same place on Front-range fault, eastern thrust of the Longmenshan thrust fault system which was broken by the 2008 Wenchuan Earthquake in China? To answer this question,we mapped co-seismic surface deformation produced by the 2008 Wenchuan Earthquake and selectively excavated four trenches at Bailu,Jiulong,Hanwang,and Yong’an along the Front-range fault. The main results are as follows: 1 )The co-seismic surface deformation zone produced by the 2008 Wenchuan Earthquake was basically coincident with the pre-existing fault,the Tongji - Anchang segment, showed on the Chinese Region Geological Map ( scales of 1 : 200,000). 2) The co-seismic rupturing was along the old faulting scarp or valley from Bailu to Bajiao. 3) The linear scarp near the village of Yong’an, departure from the pre-existing fault, was an abandoned riverside, which should not be used as an evidence of the recently proposed dextral strike-slip movement during the Late Quaternary. 4 )At least one paleo-earthquake was revealed by trenching in Bailu and Hanwang. Based on synthesizing these results, we considered that severe earthquakes were occurring repeatedly at the same location along the Late Quaternary active Front-range fault and the 2008 Wenchuan Earthquake was the latest one. We thus suggest that the re-building location be away from the active Front-range fault.更多还原