Abstract: The comprehensive characteristics of active faults,physical mechanism of fault basins,pole direction of drainage system and fault plane solution of moderate and small earthquakes indicate that recent tectonic stress fields in the study area trend from NNW to nearly SN.It follows that local tectonic stress fields in the area is related to the tectonic deformation of upper crust,caused by slipping to the south of Sichuan-Yunnan block in which the fault basin in the area has been a pull-apart basin of the surface crust since the Neogene.The boundary faults of the basins tend to be in the form of the shovel and to be down to at a depth of 1-2 km,and moderate/small earthquakes are concentrated at a depth less than 20 km,which suggests a strain release of two sorts at different depths in the slipping process.It is possible that the lower part of the crust is in the process of being deformed to northeast between the large-scele platas.Earthquakes of >M 6 with characteristic of high-angla strik-slip mainly concetate at a depth of 20-25 km which is partly related to NE compressive stress.The intersection of large-scale and local stress fields may be representative of tectonic stress at different depths.Of course,the Hounghuo River fault zone in the presence of shear-tension obviously has an effect on shifting of the stress field direction of this region.

摘要： 通过区内活断层性质、盆地生成和水系分布极向等的研究,进一步从地质上论证了该区北北西—近南北向的现代构造应力场。认为这一局部应力场是川滇菱块作南向滑移引起的地壳上部的构造变形事件。晚新生代以来的断陷盆地是这一滑移过程造成的地壳表层的拉分盆地。在地壳的下部有可能受到大区域板块北(偏东)向推挤作用的影响。中小地震和强震在深度分布、破裂特征及应力方向上的区别有可能是这种不同深度层次上应力差异作用的某些信息。