滇缅活动地块构造应力场研究

本文收集了1976—2017年滇缅活动地块98个M_W 4.8—7.0地震的震源机制解，分析震源机制解和震源深度的空间分布特征，探讨了其构造动力学背景。结果表明:①滇缅活动地块震源深度优势分布范围为10—30km，90%以上的地震震源深度小于30km，结合研究区统计时段内地震震源深度、优势度、众数等参数，推断滇缅活动地块及周边震源深度的下界为30km，脆性多震层位于10—30km，且主要位于15km附近；②滇缅活动块体不同断裂带、块体内部各次级块体之间、块体内外表现出不同的震源机制解，在空间上存在着明显的分区性特征，揭示出位于青藏高原东南缘的滇缅活动块体及周边地区应力场的非均匀性；③滇缅活动地块区域构造应力场明显受周边板块作用的控制，活动地块内部由于构造格局及其运动的差异，应力状态具有明显的区域特征。根据研究区各主要断裂带所反映的与构造背景作用一致的震源机制分布特征，可以将滇缅活动地块初步分为3个应力区。

Study on Tectonic Stress Field of Yunnan-Myanmar Active Block

In this study, focal mechanism solutions for 98 earthquakes M_W 4.8-M_W 7.0 the in Yunnan-Myanmar active block in last 41 years were collected. We analyzed the focal mechanism solution and the spatial distribution characteristics of focal depth, and discussed related tectonic dynamics. The results are:①The dominance range of seismic depth is 10-30km. More than 90% of the earthquake depth is less than 30km. According to the range, dominance, and mass of seismic depth in the statistical period of our study area, we infer that the bottom of seismic depth locates at 30km. The brittle seismogenic layer is situated between 10-30km and mainly located near 15km. ②The spatial distribution of focal mechanism solutions in the study area has obvious regionalization characteristics. This reveals the inhomogeneity of stress fields in the Yunnan-Myanmar active blocks and surrounding areas. ③The regional tectonic stress field of the Yunnan-Myanmar active block is obviously affected by the action of surrounding plates. Due to the difference of tectonic patterns and movements, the stress system has obvious regional characteristics. According to the distribution characteristics of the focal mechanism, which are consistent with the tectonic, the stress division of the Yunnan-Myanmar active block can be divided into 3 parts.