三峡水库蓄水后仙女山断裂北段数值模拟及其孕震机理研究*
吴建超,陈蜀俊,陈俊华,蔡永建

(中国地震局地震研究所(地震大地测量重点实验室),湖北 武汉 430071)

三峡水库; 仙女山断裂; 数值模拟; 孕震机理; 水库地震

Numerical Simulation of the Xiannushan Fault's North Segment and its Seismogenic Mechanism Study after the Impounding of the Three Gorges Reservoir
WU Jianchao,CHEN Shujun,CHEN Junhua,CAI Yongjian

(Key Laboratory of Earthquake Geodesy, Institute of Seismology, CEA, Wuhan 430071, Hubei, China)

three Gorges reservoir; Xiannushan Fault; numerical simulation; seismogenic mechanism; reservoir induced earthquake

备注

基于线弹性理论有限元方法,建立三峡库首区的三维有限元模型,模拟计算了库首区尤其是仙女山断裂北段在蓄水后的全位移场和构造应力场变化。结果 表明:三峡水库175 m水位蓄水,造成仙女山断裂和九畹溪断裂北段处于全位移场归州低值区和新滩高值区的梯度带上; 同时,仙女山断裂和九畹溪断裂北段深部3组主应力值较蓄水前陡增。这样的地段全位移差值变化明显,3组主应力值增高,剪应力和剪应变能易于集中,容易加速仙女山断裂和九畹溪断裂北端失稳而诱发水库地震。

Based on the finite element method of linear elastic theory, we established a 3D finite element model of the head area of the Three Gorges Reservoir. Then we calculated the total displacement field and the tectonic stress field in the head area, especially in the north segment of the Xiannushan Fault after the impoundment of the Three Gorges reservoir. The results show that: after the water level of the three Gorges reservoir reached 175 m, the north segment of the Xiannushan Fault and Jiuwanxi Fault lied in the gradient zone between low-value area of total displacement field in Guizhou and high-value area of it in Xintan. Meanwhile, after the impoundment, the three groups of principal stress in the deep of the north segment of two faults increased sharply corresponding to that before the impoundment. The total displacement value changed obviously and the principal stress continued to increase in the study area where the shear stress and the shear strain are easy to accumulate. So it will accelerate the buckling and slipping of the north segment of the Xiannushan Fault and Jiuwanxi Fault to induce the seismic activity.