GPS约束下九寨沟地区断裂带现今运动速率的非连续接触模拟研究

Research on Current Crustal Deformation in the Jiuzhaigou Area under the Constraints of GPS Results by Discontinuous Contact Model

以中国地壳运动观测网络2009—2013年GPS观测数据为边界条件,使用非连续接触有限元技术构建九寨沟地区二维有限元模型,在不确定性分析的基础之上,计算区内主要断裂带现今运动速率。研究结果表明:在巴颜喀拉块体整体近于NE向的推挤过程中,九寨沟地区的塔藏断裂、虎牙断裂、树正断裂均呈现为较高的左旋走滑兼具挤压的现今运动特征;岷江断裂、龙日坝断裂和龙门山断裂则呈现为右旋走滑兼有挤压的运动特性。结合区域主应变率计算结果,发现九寨沟地区仍然具有较高的应变积累背景。树正断裂作为2017年8月8日九寨沟M7.0地震的发震断层,其现今左旋滑动速率为3.0 mm/a,与东昆仑断裂带玛沁—玛曲段附近的左旋走滑速率4.1mm/a基本匹配,说明该断裂可能是东昆仑断裂带东端分支断裂之一,而东昆仑断裂与虎牙断裂之间的历史地震空区可能已被九寨沟地震事件贯通。

The interpolated GPS observation data during the 2009-2013 period of the China crustal movement observation network was applied to gain the boundary conditions of 2-D element discontinuous model which was used to simulate the slip rates of the fault system in the Jiuzhaigou area and undertake uncertainty analysis over it.The study turned out that the NE direction movement of Bayan Har block had been hindered by the South China block.The eastern Kunlun fault,Tazang fault,Huya fault and Shuzheng fault showed a left-lateral strike slip and compressional characteristic,when the Minjiang fault,Longriba fault and Longmenshan fault showed a right-lateral strike slip and compressional characteristic.Combined with the calculation results of regional principal strain rate,it shows that the Jiuzhaigou area still has a high background of strain accumulation.As the seismogenic fault of the August 8,2017 Jiuzhaigou M 7.0 earthquake,the left-lateral slip rates of Shuzheng fault is about 3 mm/year,which basically matched the slip rate of the eastern Kunlun fault.It is suggested that the fault may be one of the branch of the eastern Kunlun fault zone and the gap between the east Kunlun fault and the Huya fault may have been split by the Jiuzhaigou earthquake.