对汶川地震小鱼洞地表破裂带的调查分析

2008年5月12日的汶川8.0级地震使龙门山断裂带形成了3条同震地表破裂带,这表明有多条活动断层同时参与地震破裂,其过程复杂,现象丰富。本文对小鱼洞地表破裂带及其与另2条地表破裂带的交汇区域进行了野外调查,并对小鱼洞地表破裂带的活动性质和展布特征进行了分析。小鱼洞地表破裂带位于彭州市小鱼洞镇附近,是汶川8.0级地震形成的一条走向NW的逆冲并具有左旋走滑分量的同震地表变形带。调查结果显示,小鱼洞地表破裂带表现出明显的分段性特征：小鱼洞镇一带的中段,逆冲量和走滑量最大;小鱼洞镇向东南方向延伸的南段,逆冲量和走滑量逐渐变小;小鱼洞镇向西北方向进入山区的北段,则表现为以逆冲为主的活动性质。

Research on Xiaoyudong Surface Rupture Zone of the M8.0 Wenchuan Earthquake

The M 8.0 Wenchuan earthquake of 12 May,2008 generated three surface rupture zones along the Longmenshan fault zone.The complex rupture process generated various phenomena which proved multiple faults have joined in.The Xiaoyudong surface rupture zone and the intersection area of the other two surface rupture zones are investigated in this paper,and the characteristics and distribution of Xiaoyudong surface rupture zone are summarized.The Xiaoyudong surface rupture zone is located near the Xiaoyudong town,Pengzhou city.It is a coseismic surface rupture zone in the M 8.0 Wenchuan earthquake,characterized as NW-thrust fault with sinistral strike-slip displacement.Our research shows that the Xiaoyudong surface rupture zone has different characteristics in each segment： The maximal horizontal and vertical displacement is located in the middle segment in the Xiaoyudong town;The horizontal and vertical displacement of south segment is gradually diminishing towards the southeast of Xiaoyudong town;The north segment,in the mountains to the northwest of Xiaoyudong town,mainly demonstrates thrust activity.