小江断裂中段及其邻近地区应力场时间变化分析

研究地壳构造应力状态及其时空分布特征,特别是应力变化的信息,是探讨地震成因、分析发震条件的重要有效途径之一.本文利用1998年1月至2009年1月以来小江断裂中段及其邻区ML≥2.5的共计740个震源机制解,基于小江断裂中段及其邻近地区地质构造背景,对研究区进行了分区；以该区域内较大地震为界,结合余震时间序列特征,进行...

Possible crustal stress change in middle section of Xiaojiang fault and its adjacent area

The study on temporal and spatial crustal stress change is important for exploring earthquake origin and seismogenic condition. Based on 740 focal mechanism solutions of MLge;2.5 earthquakes occurred during Jan. 1998 to Jan. 2009 in middle Xiaojiang fault and its adjacent area, the studied region was divided into sub-regions, and temporally further divided into phases with the larger earthquakes as boundary of the sub-regions. After removal of the larger earthquakes this paper inverted the focal mechanism data with the method of Gephart for the stress in main phase of each sub-region. The result indicates that the azimuth of maximum principal stress sigma;1 in 4 temporal phases of the sub-region A is approximately NNW-SSE, and in northern part of sub-region B are approximately NNW-SSE，NNW-SSE and NNW-SSE. The azimuth of sigma;1 in southern part of sub-region B is approximately NNW-SSE. The azimuth of sigma;1 in northern part of sub-region B changed significantly, while the azimuth of sigma;1 in sub-region A is relatively stable. This result may be related to the complicated structure and possible stress adjusting in northern sub-region B.The sigma;1 directions in sub-region A may indicate seismically relative stability of the central Yunnan crustal block.