小江断裂带及其周边地区构造应力场特征

 应用Snoke方法计算了2000—2009年发生在小江断裂带及其周边地区的55个中小地震震源机制解.根据震源机制解分析,该区震源错动类型主要为走滑型,其次是逆断型,与小江断裂左旋走滑运动相符.整个区域主要受到近水平的北北西—南南东向挤压,自北向南主压应力轴方位从南东转为南南东,与川滇菱形块体沿南东—南南东向的走滑和旋转运动相一致.另外,构造应力方向在0~20 km内有从北西西转为北北西的趋势,考虑力轴仰角无明显变化,认为构造应力在此深度内是相对连续的.

Characreter of tectonic stress in Xiaojiang fault zone and surrounding areas

The focal mechanisms of 55 moderate-small earthquakes(3.5≤ML≤5.6) in Xiaojiang fault zone and surrounding areas are calculated tentatively using Snoke methord.According to the result of focal mechanisms,we got some information.First,source faulting types are mainly of strike-slip fault,then thrust fault in the area of the studied time period.Xiaojiang fault zone are mainly of left-lateral strike-slip motion.The maximum compression in generally in horizontal NNW-SSE direction in the study area,The result shows that there is a clockwise rotation tendency for the direction of maximum compression from north to south in the study area,which is consistent with slip and rotation functions along the direction of SE—SSE in the inner part of the Sichuan-Yunnan rhombic block.The direction change of tectonic stress in 0—20 km under the earth’s surface is NWW to NNW,consider of there is no obvious change of elevation of compressional axis,we think that the direction of tectonic stress is relatively continuous in the range.