地震研究

提取川滇地区GPS速度场边界值作为约束条件,依据地质资料,利用ANSYS有限元模拟软件建立川滇地区三维有限元模型,将川滇地区划分为4个块体,利用静力学分析模块模拟下地壳拖曳作用及2条主要活动断裂的走滑速率。结果显示:模型四周仅加载GPS速度场边界值,川滇菱形块体位移速度较实测速度偏差明显,不满足此地区地球动力学特征,增加下地壳拖曳作用荷载后速度场模拟结果得到优化,川滇菱形块体位移速度差值减小; 研究模拟下地壳拖曳作用产生的剪切力发现,拖曳作用在小金河断裂附近由南东转向正南时才能得到最优模拟结果,暗示其对川滇菱形块体拖曳方向发生了偏转。鲜水河、小江断裂模拟走滑速率分别为8.5 mm/a,6 mm/a,与实际走滑速率具有较好一致性,优化后可对断裂带闭锁研究提供参考。

Under the constraint condition extracted by the boundary value of GPS velocity field in Sichuan-Yunnan area(96°～107°E,21° ～35°N),based on geological data,we established the three-dimensional finite element model of Sichuan-Yunnan region by using ANSYS. Then we divided the Sichuan-Yunnan region into four blocks,and simulated the lower crustal dragging and the strike-slip rates of two main active faults by using the static analysis module. The results show that when only the boundary value of GPS velocity field is loaded around the model,the displacement velocity of Sichuan-Yunnan rhombic block is obviously different from the measured velocity,which does not satisfy the geodynamic characteristics of this area. After increasing the dragging load of the lower crust,the simulation results of velocity field are optimized and the difference of displacement velocity of rhombus decreases. Simulating shear forces produced by the lower crustal dragging,it is found that the optimal simulation results can only be obtained when the direction of the dragging changes from southeast to Southeast near the Xiaojinhe fault,which indicates that the direction of the lower crustal dragging is deflected. In addition,the simulated strike-slip rates of Xianshuihe and Xiaojiang faults are 8.9 mm/a and 6 mm/a respectively,which are in good agreement with the actual strike-slip rates. The optimized results can provide reference for the study of fault zone blocking.

引言
1 川滇地区构造特征及模型建立
2 模拟结果
3 讨论
4 结论

图1 川滇地区构造简图(a)(据Shen et al,2005)及模型边界条件及块体划分(b)<br/>Fig.1 Structural outline map of Sichuan-Yunnan area(a)(according to Shen et al,2005), model boundary conditions and block division(b)

图1 川滇地区构造简图(a)(据Shen et al,2005)及模型边界条件及块体划分(b)
Fig.1 Structural outline map of Sichuan-Yunnan area(a)(according to Shen et al,2005), model boundary conditions and block division(b)

表1 块体参数<br/>Tab.1 Parameters of different blocks

表1 块体参数
Tab.1 Parameters of different blocks

图2 川滇地区断裂带模型(a)及模型网格划分(b)<br/>Fig.2 Fault model(a)and model meshing(b)in Sichuan-Yunnan region

图2 川滇地区断裂带模型(a)及模型网格划分(b)
Fig.2 Fault model(a)and model meshing(b)in Sichuan-Yunnan region

图3 川滇菱形块体底部荷载边界条件<br/>Fig.3 Bottom load boundary conditions of Sichuan-Yunnan rhombic block

图3 川滇菱形块体底部荷载边界条件
Fig.3 Bottom load boundary conditions of Sichuan-Yunnan rhombic block

图4 川滇地区实测位移场与模拟结果对比<br/>Fig.4 Comparison between actual and simulation results of displacement field in Sichuan-Yunnan region

图4 川滇地区实测位移场与模拟结果对比
Fig.4 Comparison between actual and simulation results of displacement field in Sichuan-Yunnan region

图5 川滇地区等效应力场<br/>Fig.5 Equivalent stress field in Sichuan-Yunnan region

图5 川滇地区等效应力场
Fig.5 Equivalent stress field in Sichuan-Yunnan region

图6 川滇地区断裂带模拟走滑速率<br/>Fig.6 Simulated strike-slip rate of fault in Sichuan-Yunnan region

图6 川滇地区断裂带模拟走滑速率
Fig.6 Simulated strike-slip rate of fault in Sichuan-Yunnan region

图7 川滇地区泊松比分布(据Wang et al,2010)<br/>Fig.7 Distribution of Poisson's ratio in Sichuan-Yunnan region(according to Wang et al,2010)

图7 川滇地区泊松比分布(据Wang et al,2010)
Fig.7 Distribution of Poisson's ratio in Sichuan-Yunnan region(according to Wang et al,2010)

表2 鲜水河、小江断裂走滑速度对比<br/>Tab.2 Comparison of strike-slip velocities of Xianshuihe and Xiaojiang faults

表2 鲜水河、小江断裂走滑速度对比
Tab.2 Comparison of strike-slip velocities of Xianshuihe and Xiaojiang faults

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备注

引言

1 川滇地区构造特征及模型建立

2 模拟结果

3 讨论

4 结论

期刊信息