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Title:: Study of the Co-seismic and post-seismic deformation Deduced by the Wenchuan earthquake in the Sichuan-Yunnan region by three dimensional viscoelastic finite element model

Author(s):: JIANG Fengyun¹; ZHU Liangyu¹; LI Yujiang²; (1. The Second Crust Monitoring and Application Center,China Earthquake Administration,Xi’an 710054,Shaanxi,China)(2. Institute of Gustal Dynamics,China Earthquake Administration,Beijing 100085,China)

Keywords:: the Wenchuan earthquake; Finite elements model(FEM); viscoelastic relaxation; Sichuan-Yunnan region

摘要:: 在考虑川滇地区地壳介质的横向分块、纵向分层特征,及汶川地震同震断层面静态位错上下盘非对称性的基础上,构建川滇地区地壳三维粘弹性有限元模型,研究了汶川地震对川滇地区的震后影响。结果表明:(1)震后10 a由于介质粘弹性松弛效应产生的远场水平变形在川滇菱形地块内部约0～20 mm,对其北部影响较大,南部较小,其产生的远场垂直变形较小,在川滇菱形地块大部分区域表现为0～4 mm的上升;(2)离发震断层较近的鲜水河断裂、东昆仑断裂,震后水平和垂直形变呈现高梯度带;(3)为了和汶川地震之后川滇地区强震活动进行对比,计算了主要块体边界活动断裂水平应力状态和库仑破裂应力变化。从同震及震后位移场空间分布特征、应力状态反映的断层活动特征及库仑破裂应力变化反映的断层面应力加卸载情况来看,与该区域强震活动分布在空间上存在一定的相关性。

Abstract:: Considering the characters of horizontal blocks and vertical layers of the crust and the asymmetry of the coseismic static dislocation on fault plane of the Wenchuan earthquake,we study the co-seismic and post-seismic effect deduced by the Wenchuan earthquake in the Sichuan-Yunnan region by three dimensional viscoelastic finite element model. The results indicate:(1)horizontal deformation due to the medium viscoelastic relaxation effect reaches 20mm in the Sichuan-Yunnan block ten years after the earthquake.vertical deformation due to the medium viscoelastic relaxation effect is approximately 0～4mm in most of the Sichuan-Yunnan block,and is smaller than the horizontal deformation.(2)post-seismic horizontal and vertical deformation gradient values are more obvious in the Xianshuihe and Dongkunlun faults.(3)we calculate the horizontal main stress and Coulomb failure stress changes in main faults,which agree with the distribution of the seismicity distribution in Sichuan-Yunnan regions.