缅甸作为全球受地震灾害影响甚为严重的国家之一,因缺乏区域地震观测资料,对其孕震构造环境的详细分析研究十分不足.本文利用中缅联合地球物理探测(CMGSMO)项目在缅甸布设的密集宽频带地震台阵观测数据,对印缅山脉至中央盆地的地震活动特征进行了分析.基于改进的剪切-粘贴法(generalized Cut And Paste,gCAP)新获得了28个ML3.0~5.0地震事件的震源机制解等震源参数信息,并结合全球矩心矩张量(Global Centroid Moment Tensor,GCMT)目录及其他已发表的震源机制解资料,应用区域阻尼应力场反演算法得到了研究区的应力分布状态,综合探讨了研究区域深浅部构造关系及孕震机制.研究表明印度板块持续的斜向俯冲控制着印缅山脉和中央盆地的地震活动,但其影响向东逐渐减弱,浅部最大主应力方向的变化可能反映的是局部应力集中或者是相对短时间内的应力调整,不同区域的地震活动差异主要受区域构造及其浅部断层的影响,中央盆地下方的两个邻区之间的最大主应力轴的偏转可能与深部活动相关.
Using dislocation model of seismic deformation and the hybrid global inversion method, we analyze the 1990-1995 annually GPS data from 89 stations in southern Taiwan and its neighboring area and discuss the origin of the observed deformation field. Based on the geologic investigation and seismic observation we simply assume six blocks and nineteen fault patches in the studied area. The results show that the Philippine Sea plate moves, relative to the Eurasian plate, at a velocity (69±2)mm/a in 317°±2°. About a half of the rate is concentrated on the Longitudinal Valley fault (LVF), and the other half of the convergence spread over the boundaries among the west blocks. The Philippine Sea plate and the Central Range move toward northwestward. In the west of the Central Range zone, the motion of the blocks accords with the observed fan-shape distribution of the maximum principal stress. The faults between the Western Foothills and the Coastal Plain geological provinces have main thrust components, and the dips turn small from south to north. The fault widths are about 10km, implying that they are strongly locked, and most of the large historical earthquakes occurred here.
