南水北调西线工程区及邻域的活动构造

ACTIVE TECTONICS ALONG SITE AND NEIGHBORHOOD OF WEST ROUTE OF SOUTH-TO-NORTH WATER TRANSFER PROJECT IN CHINA

南水北调西线一期工程在构造上位于青藏高原东部的巴颜喀拉地块内部,块体的四周边界以巨型走滑断裂和逆断裂为特征,构造运动非常强烈,是块体运动引发应力集中和释放能量的主要场所。但块体内部构造活动性较弱,仅发现甘德—阿坝断裂系北支断裂在阿坝盆地段的部分断裂、色达—洛若断裂和康勒断裂等晚更新世以来有过活动,且规模和运动强度远小于地块边界断裂。晚第四纪以来地块边界断裂的位移速率大多在7 mm/a以上,最大达18 mm/a,最小为1～2 mm/a,而输水隧洞附近最主要的活断层顺河断裂的位移速率仅为0.18 mm/a,相对地块边界断裂小1～2个数量级,可以认为工程场地处于构造相对稳定的地区。给出了阿坝盆地北缘断裂、顺河断裂等活断裂在工程使用期内最大设防的倾滑位移量,分别为0.67和2.62 m。

The first stage project of the west route of South-to-North Water Transfer Project is located in Bayankela block interior of the eastern Qinghai-Tibet Plateau. The boundary of Bayankela block is all the giant strike-slip or thrust fault systems, which have intense activity; and the boundary belts are the primary sites of the accumulation and release of stress resulted from the blocks movement. The fault activity is weaker in Bayankela block interior than that of the boundary belts. Partial faults of Gande-Aba fault system, Seda-Luoruo fault, and Kangle fault, etc., were active at one time since Late Pleistocene epoch. However, they have weaker active intensity than the boundary belt. The average displacement rates of the block boundary faults in the late Quaternary Period were generally more than 7 mm/a; the maximum value was up to 18 mm/a, and the minimum one was 1-2 mm/a; however, the slip rate of the most primary active fault at the raceway vicinity is only 0.18 mm/a In general, the crust of the project site is relative stable. The maximum dip-offset of the faults needed to be protected for the project during useful life has been deduced; for example, for the Aba basin north marginal fault and the Shunhe fault the maximum value is 0.67 m and 2.62 m, respectively.