【摘要】 南水北调西线一期工程位于川青地块及其南缘鲜水河断裂带,地质条件复杂。GPS监测表明,川青地块及其邻区的地壳运动水平速度,具有自西向东递变下降的顺时针涡旋转动的总趋势;鲜水河断裂带有较高的移动速率;工程区东、西两侧的测站之间有一定的水平速度矢量差。工程区为高地应力区,并可产生局部高应变能带。鲜水河断裂带为我国西部的强震带;川青地块内部已发生5级以上地震25次。与中强震有关的断裂带通过工程区,并表现出工程区地壳活动性。地壳活动性将对南水北调西线一期工程建设产生重大影响。更多还原

【Abstract】 The 1st Stage Construction Project of Water Division from the South to the North via the Western Course,China,is a construction group that consists of 6 dams and 7 tunnels.It is located in a high-elevation and cold region within the western Sichuan Plateau,and geologically in the Sichuan-Qinghai Block and along its southern margin——Xianshuihe Fault Zone.Due to complex geological conditions in the construction region,and it is very important to study and measure crustal deformation and earthquake activity.The Sichuan-Qinghai Block and its marginal fault zones have been rejuvenated because of driving of plate collision and post-collision convergence between India and Eurasia since about 50 Ma.GPS monitoring data document that in the Eurasia frame,the crustal movement velocity field shows a general tendency of clockwise rotation vortex of progressively decreasing of horizontal velocity from 25.66 mm/a in the west to 6.99 mm/a in the east in the Sichuan-Qinghai Block and adjacent areas.An average left-lateral slip rate between blocks in both sides of the Xianshuihe Fault Zone is ca.8 mm/a,and the movement rate on the main fault is 9.3 mm/a of left-lateral slipping with local strain accumulation.The horizontal velocity differences between GPS stations DAR/KEY and SEX/YJW located on the east and west sides of 1st Stage Construction region are 4.1 mm/a and 11.93 mm/a respectively,and orientations of vector decline eastwards 15.3° and 5.8° correspondingly.The in-situ stress measurement data reveal that the construction region is a high in-situ stress area,and local belts with higher strain-energy may be formed in the area.Existing records document that the Xianshuihe Fault Zone is a strong earthquake belt;25 historical earthquakes(M≥5)once occurred within the Sichuan-Qinghai Block.Therefore,the Sichuan-Qinghai Block is not a inactive and stable block.In the Sichuan-Qinghai Block,continuous crustal deformation is a basic character,and another hand,stress concentration and stain accumulation locally occurs,resulting in a moderate-strong earthquake,and a diffuse shear or/and fracture belt with short length and less offset rate in a suitable situation.However,no dominant association of the earthquakes happened,but there were temporal periodicity and spatial migration along the long-axis of the block for the earthquakes.The fault zones relative to moderate-strong earthquakes,such as Daqu Fault,Sêrtar Fault,Upper Dokog Faults,and Aba Fault,cut through the construction region,indicating crustal activity in the region.The crustal activity will exert a notable impact on the 1st Stage Construction Project of Water Division from the South to the North via the Western Course,China.更多还原