林向东 徐 平 葛洪魁 武敏捷 武安绪. 2011: 小江断裂中段及其邻近地区应力场时间变化分析.. 地震学报, 33(6): 755-762.
引用本文: 林向东 徐 平 葛洪魁 武敏捷 武安绪. 2011: 小江断裂中段及其邻近地区应力场时间变化分析.. 地震学报, 33(6): 755-762.
Lin Xiangdong Xu Ping Ge Hongkui Wu Minjie Wu Anxucomult. 2011: Possible crustal stress change in middle section of Xiaojiang fault and its adjacent area. Acta Seismologica Sinica, 33(6): 755-762.
Citation: Lin Xiangdong Xu Ping Ge Hongkui Wu Minjie Wu Anxucomult. 2011: Possible crustal stress change in middle section of Xiaojiang fault and its adjacent area. Acta Seismologica Sinica, 33(6): 755-762.

小江断裂中段及其邻近地区应力场时间变化分析.

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

  • 摘要: 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MLge;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,进行时间上的分段;去除较大地震后,采用最长距离聚类分析方法对各分区的地震进行了分类.在此基础上,利用Gephart 的应力张量反演方法,根据震源机制解资料反演出了各分区的优势应力场.结果表明,在观测时段内,根据构造和震源机制,可将研究区域分为A和B两个区域. A区最大主应力sigma;1 方位在4个时段内大致为NNW向, B区北部在4个时段内sigma;1 方位大致为NNW向、WNW和ENE向. 从应力结构看,A区和B区北部应力以水平作用为主. B区南部sigma;1 方位大致为NNW向,仍以水平作用为主; B区北部sigma;1 方位变化较大,可能与B区北部地质结构复杂、应力调整活跃有关.而A区主应力方位相对稳定,显示了滇中块体的稳定性.

     

    Abstract: 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.

     

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