Abstract: Based on the investigation of active faults in region we have obtained the recent tectonic stress field in Northwest Yunnan Province and its adjacent areas using the method of determination of principal stress axes from field measurements of slickensides. The result shows that thereceut tectonic stress field in the region is characterized by horizontal componment. The directionof maximum principal stress in Northwest Yunnan is different from that in the surrounding areas. Analysis of active tectonic pattern shows that Northwest Yunnan active tectonic region is aantithetic S extension region with NW-trending strike slip faults. This may be better for explaining the tectonic origin and the state of recent crustal stress in the region.

Key words: Northwest Yunnan, Fault slip direction, Tectonic stress tensor, Antithetic S－type dextral extension

摘要： 通过滇西北及邻区大量活动断层擦痕的测量和利用由断层滑动方向反演构造应力张量的计算方法,获得滇西北及邻区现代构造应力场特征:区域现代构造应力场以水平作用为主,在滇西北地区,最大主应力方向为北北东;在滇西北外围地区,最大主应力方向为北北西或北西。在构造应力场分析的基础上,依据活动断裂构架及运动组合特征,提出了滇西北反“S”型右旋扩展的构造成因模型。

关键词: 滇西北, 断层滑动方向, 构造应力张量, 反“S”型右旋扩展