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.
Seismogenic settings in the Indo-Burma Ranges and Central Basin in Central Myanmar
Myanmar is one of the countries suffered from severe earthquake disasters in the world,and its seismogenic settings are complex and not well studied due to inadequate seismic observations.In this study,we analyzed the seismicity in the Indo-Burma Ranges and Central Basin in Myanmar using data from the densy seismic array of China-Myanmar Geophysical Survey in the Myanmar Orogen project,derived 28 new earthquake focal mechanisms of ML3.0～5.0 by the generalized Cut-and-Paste inversion method,and inverted the regional stress field using damped regional-scale stress inversion technique with some focal mechanisms from Global Centroid Moment Tensor(GCMT)and other published work.Then we discussed the deep and shallow tectonic and seismogenic settings and its mechanism in the study area.Our results indicate that the continuous oblique subduction of the Indian plate controls the seismicity in the Indo-Burma Ranges and Central Basin,but its influence declined with the eastward subducting.The changes of the maximum principal stress direction in the shallow might be caused by stress concentration or the fast adjustment of local stress.The difference stress patterns in various zones are mainly affected by the subduction angle,and the shallow seismicity as well as the asthenosphere activity in the deep.The different regional seismicity is mainly affected by the complexity of fault systems and tectonic settings.
万方数据
维普
