论文部分内容阅读
在龙门山中段小鱼洞地区映秀-北川断裂和彭县-灌县断裂发生了同震位移,同时在该地区新出现了一条北西向的同震破裂带——小鱼洞断裂的破裂带,并分割了两条近于平行的北东向逆冲-走滑型的主断裂。汶川特大地震发生后重点对小鱼洞断裂的地表破裂开展了详细的野外地质填图,利用全站仪和GPS对地表破裂进行了精确的测量。初步调查的结果表明,小鱼洞断裂位于映秀-北川断裂与彭县-灌县断裂之间,走向近于北西向,延伸约15km,以脆性破裂为特征,穿过小鱼洞大桥,并切割了多种类型的地貌单元,使道路发生拱曲、破坏和桥梁垮塌或移位。单个破裂长度在几米到300m不等,其南西盘为上升盘,北东盘为下降盘,平均垂直位错为1.0m,平均水平位错为2.3m,垂直与水平位错量之比1:1～1:2,显示为逆冲分量小于或等于左旋走滑分量,并以左旋走滑作用为主。同时,研究表明小鱼洞断裂属于映秀-北川断裂与彭县-灌县断裂之间的捩断层,其主要特征包括:1)是在汶川地震中由于龙门山逆冲体之间的差异逆冲运动过程中而形成的断裂;2)其走向近于北西向,垂直于龙门山北东向的主干断裂,而平行于逆冲体的逆冲运动方向;3)具有高角度断面的断层,以左旋走滑作用为主。
The coseismic displacements have taken place in Yingxiu-Beichuan fault and Pengxian-Guanxian fault in Xiaoyudong area in the middle of the Longmen Shan area. At the same time, a northwesterly coseismic rupture zone-Xiaoyudong fracture zone has emerged in the area, And split two near-parallel north-east thrust-strike-slip major faults. After the Wenchuan earthquake, the paper focused on the surface rupture of Xiaoyudong fault and carried out detailed field geologic mapping, and measured the surface rupture by total station and GPS. The results of the preliminary survey show that the small fish hole fracture is located between the Yingxiu-Beichuan fault and the Pengxian-Guanxian fault and extends nearly 15km northwestward, characterized by brittle fracture, crossing the Xiaoyudong bridge and cutting Various types of geomorphological units have been used to vault, damage and collapse or displace the bridge. A single rupture length ranging from a few meters to 300m, the Southwest plate for the rising plate, the North East plate for the descent plate, the average vertical dislocation of 1.0m, the average horizontal dislocation of 2.3m, the amount of vertical and horizontal dislocation ratio of 1: 1 ~ 1: 2, showing that the thrust component is less than or equal to the left-hand strike-slip component and is dominated by left-lateral strike-slip. At the same time, the study shows that Xiaoyudong fault belongs to the fault between Yingxiu-Beichuan fault and Pengxian-Guanxian fault. Its main features include: 1) It is due to the difference between Longmenshan thrust body in Wenchuan earthquake 2) its strike is near northwest, perpendicular to the northeastern Longmen Mountains main fault, and parallel to the direction of the thrust movement of the thrust; 3) high angle section of the fault to the left The main role of slippery.