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应力场在地球动力学研究方面起着至关重要的作用。本研究给出了由震源机制解数据反演应力张量及其置信范围的网格搜索法。我们使用人工合成震源机制解数据对该算法进行了测试,人工合成的震源机制解数据由拉张型、挤压型和走滑型3种类型应力场生成,并对生成的震源机制解数据添加不同水平的噪声。测试结果表明,相对于传统方法,本研究给出的方法反演出的应力场精度得到显著提高。本文算法主要有以下3个优点:(1)由精细的网格搜索获得应力张量的全局最优解,搜索网格为1°×1°×1°×0.01,避免了搜索结果落入局部最小值;(2)在反演应力张量的过程中,本方法可以考虑震源机制解数据精度的不同,并赋予不同的权重;(3)由F检验给出应力张量结果的置信范围。我们将该方法应用于中国、越南和老挝的边界地区,获得该地区应力场的主压应力方向为SSE—NNW,主张应力方向为NEE—SWW。应力比R为0.6,这意味着应力张量的特征值接近等差数列。该地区应力场与奠边—琅勃拉邦弧形断裂的左旋走滑性质一致,所得结果对该地区的地质动力学过程研究有一定的帮助。
Stress field plays a crucial role in geodynamics research. In this study, a mesh search method is proposed to retrieve the stress tensor and its confidence range from focal mechanism solution data. We tested the algorithm using synthetic focal mechanism solution data. Synthetic focal mechanism solution data were generated from three types of stress fields: tensile, extrusion and slippery, and the focal mechanism solution data was added Different levels of noise. The test results show that compared with the traditional method, the accuracy of the stress field obtained by the method given in this study is significantly improved. The main advantages of this algorithm are as follows: (1) The global optimal solution to stress tensor is obtained from the fine grid search, and the search grid is 1 ° × 1 ° × 1 ° × 0.01, which avoids the search results falling into the local (2) In the process of inverting the stress tensor, this method can consider the different accuracy of the focal mechanism solution data and give different weights; (3) Confidence range of stress tensor results is given by F-test. We apply this method to the boundary regions between China, Vietnam and Laos. The principal compressive stress direction of the stress field in this area is SSE-NNW, and the stress direction is NEE-SWW. The stress ratio R is 0.6, which means that the eigenvalues of stress tensors are close to the arithmetic progression. The stress field in this area is consistent with the left-lateral strike-slip nature of the dyke-Luangprabang arc fault. The results obtained will be helpful to the study of the geodynamic process in this area.