苏门答腊巨大地震前后的区域应力状态  

Regional stress state before and after Sumatra Earthquake

作　　者：程万正[1] 阮祥[1] 江在森[2] 

机构地区：[1]四川省地震局预报研究所,四川成都610041 [2]中国地震局预测研究所,北京100036

出　　处：《四川地震》2012年第4期1-9,共9页Earthquake Research in Sichuan

基　　金：国家自然科学基金项目(41090294)资助

摘　　要：研究了2004年印尼苏门答腊巨大地震前后安达曼—苏门答腊大断裂带与缅甸实皆大断裂至中国中部南北地震带中南段的地震矩张量解资料,采用力轴张量计算法研究了各构造区(段)平均应力张量,结合大范围连续定点GPS观测资料的分析,给出巨大地震前后应力场的变化特征。苏门答腊巨大地震前后主压应力方位大体一致,震后呈现的张应力方位发生一定变化,作用力更陡。苏门答腊—安达曼大断裂带附近,地震多属逆倾滑动类型,少量为走滑错动类型,2004年12月26日苏门答腊9.0级地震后走滑错动型地震有明显增加。沿缅甸实皆大断裂至中国中部的南北地震带,震前倾滑和走滑型地震比例相当,而震后走滑错动型地震减少。2004～2007年印尼苏门答腊3次巨震虽然距青藏高原及边缘较远,巨大地震破裂造成相当大区域应变释放的影响是显著的,也是整体性的。分析结果表明,青藏高原东缘地区随印尼巨震过程,2003～2005年基线伸长变化,呈现的应力应变状态是拉张,2006年以来转平或缩短,基线缩短量有较明显增大,呈现为几次巨大地震后的恢复状态。研究得到的大区域应力场和大尺度地壳变形场的微动态呈现板块间汇聚挤压与恢复拉张,或应力增强、松弛、再增强的变化过程。We collected and analyzed the moment tensor solutions of earthquakes occurred in three seismic belts. These seismic belts include Sumatra-Andaman fault zone in Indonesia, Sagaing fault in Burma and the middle-south seismic belt of the south-north seismic zone in central China. All of the earthquakes occurred around the time when the Indonesian Sumatra earthquake happened in 2004. By using the stress tensor calculation method, the mean stress tensors of each tectonic zone were obtained. Linking with the analysis of continuous GPS observation data at fixed points in big range, the dynamic characteristic of stress field before and after the great earthquake could be summarized. The directions of main stress were roughly consistent before and after Sumatra great earthquake oc- curred. The direction and intensity of tensile stress changed somewhat and steeply, respectively. In Sumatra-Anda- man fault zone, most of the active types of the seismic faults before the Sumatra great earthquake were reverse dip- slip and a few were strike-slip, and strike-slip seismic faults were distinctly on the increase after the Sumatra MW9. 0 earthquake on 26 December 2004. In the area stretching from Sagaing fault to the south-north seismic zone in central China, dip-slip and strike-slip seismic faults were equivalent before the Sumatra great earthquake, and strike-slip seismic faults decreased relatively after the earthquake. Although 3 large earthquakes happened in Indo- nesian Sumatra between 2004 and 2007 were far distant from Qinghai-Tibet Plateau and its edge, the effect of strain release in a region of considerable extent caused by large earthquake ruptures was distinct and integral. Analysis shows that, on the eastern edge of Qinghai-Tibet Plateau, baselines were extended and the state of stress and strain was in tension between 2003 and 2005, and it assumed restoring state of large earthquakes had happened that the magnitude of baseline shortening had increased distinctly since 2006. Micro-dynamic of stress field in large area

关 键 词：应力张量 震源机制 GPS观测 地壳运动 苏门答腊地震 南北地震带 地震趋势 

分 类 号：P315.727[天文地球—地震学]