云南普洱-宁洱地区变形及应力场的有限元模拟

The Deformation and Stress Fields by Finite Element Method of Pu'er-Ninger Area in Yunnan Province

为研究普洱-宁洱地区强震频发与构造应力场和变形场的相关性,以1997—2007年GPS数据计算得到的云南普洱-宁洱块体年运动量为边界约束,建立云南普洱-宁洱地区包含红河断层及澜沧江断层等10个断层的三维摩擦接触有限元模型,计算在GPS年运动速率约束下棋盘式构造格局的变形位移场、应变场及应力场分布,并将计算结果与GPS计算结果进行比较。通过计算发现:普洱-宁洱断层群会使澜沧江及红河断层包围区域变形及应力场更复杂,普洱-宁洱地区复杂变形及应力场可能是该地区中强地震频发的主要原因;镇远-普洱断层可能是影响普洱-宁洱地区变形及应力场的主要断层;普洱-宁洱地区走向共轭断层交汇处,存在较大变形及应力值;变形场与应力场会随断层走向变化而发生变化,在断层走向变化剧烈部位有较大值。

In this paper, we study the possible correlation between the strong earthquake and tectonic stress or deformation. By applying the computational result from the GPS data of Pu＇er-Simao area in Yunan Province as the boundary condition, we construct the 3D frictional contact finite element model of Pu＇er-Simao area containing more than 10 faults besides Lancang and Red fiver fault. Then, we compute spatial distribution of deformation displacement strain and stress field. We compare the numerical result of deformation displacement with GPS data. Through the computation, we find that the presence of fault group in Pu＇er-Simao area will affect the deformation and stress field in the area between Lancang river and Red river fault and will make the deformation and stress field more complex. The complex tectonic stress and deformation field is the main cause to the strong earthquakes. Zhenyuan-Pu＇er fault is perhaps the main fault which affects the deformation and stress field in the Pu＇er-Simao area. There are relatively large stress deformation strain and displacement in the place where the NNW and NEE strike faults meet in the Pu＇er-Simao area. Both the deformation and stress field will vary with the strike of fault, especially, there will have relatively large deformation and stress value at the position where the fault strike change orientation greatly.