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Title:: Quantitative Results and Confidence Interval Analysis of the Stress Field in Hunan Region

作者:: 田优平¹; 沈平¹; 万永革²; 3; 唐红亮¹; 康承旭¹; 姚海东¹; 佘旭明¹; 叶世山⁴; (1.湖南省地震局湖南省震灾风险防治中心,湖南长沙 410004; 2.防灾科技学院,河北三河 065201; 3.河北省地震动力学重点实验室,河北三河 065201; 4.广东省地震局,广东广州 510070)

Author(s):: TIAN Youping¹; SHEN Ping¹; WAN Yongge²; 3; TANG Hongliang¹; KANG Chengxu¹; YAO Haidong¹; SHE Xuming¹; YE Shishan⁴; (1.Hunan Earthquake Disaster Risk Prevention Center,Hunan Earthquake Agency,Changsha 410004,Hunan,China)(2.Institute of Disaster Prevention,Sanhe 065201,Hebei,China)(3.Hebei Key Laboratory of Earthquake Dynamics,Sanhe 065201,Hebei,China)(4.Guangdong Earthquake Agency,Guangzhou 510070,Guangdong,China)

Keywords:: stress field; the grid-trial method; the grid-search method; confidence interval; Hunan region

摘要:: 基于湖南及其邻区312个地震的529条P波初动极性数据和32个M_L≥2.8地震的震源机制解,采用格点尝试法和网格搜索法分别反演得到了湖南地区构造应力场的定量结果和置信范围。格点尝试法计算得到的P轴方位和倾伏角分别为102°和10°,T轴方位和倾伏角分别为237°和76°; 网格搜索法反演得到的P轴方位和倾伏角分别为100°(置信区间为79°～100°)和5°(置信区间为2°～5°),T轴方位和倾伏角分别为225°(置信区间为204°～225°)和81°(置信区间为81°～82°)。结果表明:湖南地区平均震源机制解表现为逆断型; 主压应力轴优势方位为NWW向,倾伏角近乎水平; 主张应力轴优势方位为NE—NEE向,倾伏角较大。对两种方法得到的研究区应力场结果进行了可靠性分析并与前人结果进行了对比,证实本文结果的可信度较高。

Abstract:: Based on 529 P-wave polarity data of 312 earthquakes and the focal mechanism of 32 earthquakes with magnitude over 2.8 in Hunan and its neighboring region,we obtain the quantitative results and confidence ranges of the tectonic stress field in Hunan region by using the grid trial method and the grid search method respectively.The mean stress field calculated by the grid trial method shows that the azimuth of P-axis is 102°,the dip angle of P-axis is 10°,and the azimuth and dip angle of T-axis are 237° and 76° respectively.The results from the grid search inversion show that the azimuth and dip angle of P-axis are 100° when confidence interval is 79°-100°,and 5° when confidence interval is 2°-5°,and the azimuth and dip angle of T-axis are 225° when confidence interval is 204°-225°,and 81° when confidence interval is 81°-82°.According to the results of two stress field algorithms,the average focal mechanism proves to be reverse fault in Hunan region.The dominant direction of the principal compressive stress is NWW,and its dip angle is almost horizontal.The dominant direction of the principal tensile stress is NE-NEE,and its dip angle is large.We analyze the reliability of the inversion results from two algorithms,and compare with the previous study,and prove that the results proposed in this paper is of high reliability.