汶川地震对芦山地震孕震环境影响的数值模拟  

Numerical simulation study on the impact of the Wenchuan earthquake to the seismic environment of the Lushan earthquake

作　　者：郭颖星[1] 祝爱玉[1] 张东宁[1,2] 

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]中国地震局地震观测与地球物理成像重点实验室,北京100081

出　　处：《科学通报》2017年第17期1882-1895,共14页Chinese Science Bulletin

基　　金：中国地震局地震行业科研专项(201408014);中国地震局基本业务专项(DQJB16B06);国家自然科学基金(41504079)资助

摘　　要：利用有限元数值模拟方法,以汶川地震和芦山地震的野外地质调查、同震位移和汶川地震前形变观测结果为约束,分析研究了高海拔地形蓄积的重力位能作用下,中地壳低速层的存在以及中央断裂和前山断裂同时破裂的条件下汶川地震的发生对龙门山南段孕震环境的影响.模拟计算结果显示,在一定的模型壳幔介质属性及空间结构下,龙门山断裂带西侧低速层的存在、青藏高原向四川盆地过渡带的地形特征以及汶川地震时中央断裂和前山断裂同时破裂的条件,是控制汶川地震对芦山地震孕震环境影响程度的重要因素.其中,地形和低速层对汶川地震引发的芦山地震孕震环境库仑破裂应力变化的影响最为显著,在所选剖面的北东段,地形特征的影响更为明显,而汶川地震双破裂面的影响则较小.The finite element numerical simulation method was used to investigate the impact of the Wenchuan earthquake on the seismic environment of the southern Longmenshan Mountain. The three-dimensional viscoelastic geological model, including the Longmenshan front-range fault, central fault, back-range fault, the Bayan Kala block, and the South China block, was constrained by the results of the geological survey, coseismic dislocation, and the GPS observation of Wenchuan and Lushan earthquakes. We studied how the calculation results were influenced by gravity potential energy caused by high altitude topography, the low velocity layer in the middle crust and the rupture of the Beichuan-Yingxiu and Jiangyou-Guanxian faults, by modifying the parameters of a model. The Wenchuan earthquake was simulated by reducing the Young＇ s modulus of the possible generating fault. We calculated the Coulomb stress of the Dayi blind fault, Dachuang-Shuangshi fault, and the ＂Y＂-shaped blind thrust fault between the two faults above. The simulation results show that the Coulomb stress has a similar distribution on the fault planes of the southern Longmenshan faults zone caused by the Wenchuan earthquake, considering the low-velocity layer or the double-rupture surface. The Coulomb stress on the top of the Dachuan-Shuangshi fault surface was about 0 MPa, and it gradually reduced towards the southwest direction. At the source of the Lushan earthquake, the Coulomb stress was about -0.02 MPa. For the west branch of ＂Y＂-shaped fault, the Coulomb stress on the fault surface was significantly reduced and was about -0.02--0.03 MPa at the source of the Lushan earthquake; after the Wenchuan earthquake, the Coulomb stress on the east branch of the ＂Y＂-shaped fault plane was about -0.01-0.03 MPa; for the Dayi fault, the Coulomb stress was increasingly obvious on the fault surface from the southwest to the northwest after the Wenchuan earthquake. Therefore, the Wenchuan earthquake could reduce the risk of an earthquake on the Dachuan-Shua

关 键 词：汶川地震 芦山地震 孕震环境 库仑破裂应力 数值模拟 

分 类 号：P315.2[天文地球—地震学]