云南及邻区地壳应力场研究

地壳应力场对探讨区域构造动力过程和形变机制有重要意义.为了获得云南及邻区精确的构造应力场以及确定先前研究中存在差异地区的构造应力场，本研究首先在搜集研究区已有震源机制解的基础上，使用gCAP方法反演了近年来发生的地震震源机制解，共获得研究区震源机制解1302个; 其次，在应力场反演时，提出了定量设置反演网格大小的方法，并删除阻尼和无阻尼反演应力场结果性质存在差异的网格.最终，基于大量震源机制解资料获得研究区精确的应力场：（1）云南及邻区震源机制解类型以走滑型为主，遍布整个研究区，逆走滑和逆冲型地震集中分布在云南与四川盆地交界地区，正断型和正走滑型地震较少，主要分布在滇西和滇西北地区; 研究区震源机制解的多样性，在一定程度上反映了研究区构造活动和应力场的空间差异性.（2）云南及邻区整体应力场表现为：主压应力轴方位迹线呈以西北角为中心的扇形分布，主张应力轴方位迹线呈以西北角为中心的弧形分布，总体上反映青藏高原物质向东南的运移作用对研究区应力场具有控制作用.（3）研究区应力场类型以走滑型为主，局部地区出现逆冲和拉张型应力场，所得结果与前人应力场研究结果总体上一致.（4）腾冲火山区地壳应力场为走滑型，与腾冲地区断裂以走滑型为主相一致，一定程度上揭示出现今火山活动对浅部地壳应力场的影响较小.

Study on the crustal stress field of Yunnan and its adjacent areas

The tectonic stress field is essential for understanding the regional dynamic tectonics and deformation mechanism. To obtain the accurate tectonic stress field in Yunnan and its nearby regions, and to analyze where there are discrepancies in stress fields in previous studies, we collect the existing focal mechanism solutions and invert the focal mechanism solutions of earthquakes that occurred in recent years, using the gCAP method. In total, 1302 focal mechanism solutions were obtained within the study area. Then, we propose a method for quantitatively setting the grid size for the regional stress field inversion, and remove the grids with different stress field results between damped and undamped inversions. Based on a large number of focal mechanism solution data, the accurate stress field in study area is obtained, summarized as follows. First, the types of focal mechanism solutions in Yunnan and its adjacent areas are mainly strike-slip, which is distributed throughout the study area. Thrust with strike-slip and thrust earthquakes are mainly distributed in the border area between Yunnan and Sichuan Basin, while normal fault and normal with strike-slip earthquakes are less, and mainly distributed in western and northwestern Yunnan. To some extent, the diversity of focal mechanism solutions in the study area reflects the spatial differences of tectonic activities and stress fields. Second, the overall stress field in Yunnan shows that the azimuth trajectory of the principal compressive stress axis is distributed in a fan shape with the northwest corner as the center, and the azimuth trajectory of the principal extensional stress axis is distributed in an arc shape with the northwest corner as the center, which reflects that the migration of materials from the Tibeten Plateau to the southeast has a controlling effect on the stress field in the study area. Third, the stress field in the study area is mainly strike-slip faulting, with thrust and normal stress regime existing in a few areas, and the results are generally consistent with the previous research results. Finally, the crustal stress field in Tengchong volcanic area is strike-slip faulting, which is consistent with the strike-slip-dominated faults in Tengchong area. To some extent, it implies that the current volcanic activity has little influence on shallow crustal stress field.