2015年尼泊尔Ms8.1地震构造成因及对青藏高原及邻区未来强震趋势的影响  

Tectonic Genesis of the 2015 Ms8.1 Nepal Great Earthquake and its Influence on Future Strong Earthquake Tendency of Tibetan Plateau and its Adjacent Region

作　　者：吴中海[1,2] 赵根模[1,3] 刘杰[1,4] 

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]国土资源部新构造运动与地质灾害重点实验室,北京100081 [3]天津市地震局,天津300201 [4]首都师范大学资源环境与旅游学院,北京100048

出　　处：《地质学报》2016年第6期1062-1085,共24页Acta Geologica Sinica

基　　金：国家自然科学基金项目(批准号:41171009);中国地质调查局项目(1212011120163;12120114002101);中国地质科学院地质力学研究所基本科研业务费项目(DXLXJK201410)共同资助的成果

摘　　要：2015年尼泊尔Ms8.1地震的余震分布、震源机制解、震源破裂过程反演结果和喜马拉雅造山带地质构造特点表明,此次大震是印度板块沿喜马拉雅主前缘逆冲断裂向欧亚板块进行低角度俯冲的结果。地震破裂从北西向东南方向传播,累计长度达170km,最大倾向滑移量5-7m。其发震断裂全新世活动强烈,历史地震活动频率高、强度大,M≥7.5地震的原地复发平均间隔在500年左右,而在地震活跃阶段分段破裂的平均间隔只有10年左右,并且历史地震活动在最近1800年期间显示出比较明显的从西向东迁移规律。历史地震活动过程揭示,喜马拉雅主逆冲断裂带上目前存在兴都库什、尼泊尔西部、锡金-不丹和印缅交界区4个地震空区段,特别是位于此次地震东部的两个空区,未来地震危险性较显著。由于印-欧大陆俯冲碰撞作用是中国大陆现今地壳变形的主要动力来源,也是中国大陆强震频发的主要地质构造原因,这决定了喜马拉雅、青藏高原及邻区的大震活动之间存在明显的时空关联性,主要表现为大地震活跃阶段在时间上的交替出现和大地震沿垂直喜马拉雅造山带的纵向迁移过程。进一步结合青藏高原及邻区历史地震活动及未来地震危险性的分析成果推断,在喜马拉雅地震带的新一轮活跃过程中,中国大陆必将面临更为严峻的地震形势,尤其是青藏高原及邻区晚第四纪活动性显著的区域性活动构造带或断裂带的潜在强震危险性比较突出,主要包括：藏南的近南北向裂谷带与北西向右旋走滑断裂带,川滇地块中的安宁河-小江断裂带与大凉山断裂带、南汀河断裂带与畹町断裂带、澜沧-景洪断裂带和滇西北大理-丽江裂陷带,西北地区的西昆仑山前逆冲-褶皱带、阿尔金断裂带和天山的主要逆冲-褶皱变形带等。但当前活动构造调查研究的不足限制了对区域大地震危险性做出更准�Aftershock distribution,focal mechanism interpretation,inversion result of source rupture process of the 2015 Ms8.1Nepal great earthquake and Cenozoic tectonic of the Himalayan orogenic belt shows that the Ms8.1great earthquake resulted from low-angle subduction of Indian plate towards the Eurasian plate along the Main Himalayan Thrust（MHT）fault zone.The focal rupture propagated from northwest to southeast along the MHT trend,with an accumulated length of about 170 km and a maximum dip-slip displacement of about 5-7 m.The focal rupture was active at most during the Holocene,with high frequencies and high magnitudes.Along the MHT,earthquakes with Ms ≥7.5occurred very 500 years and the average interval of earthquake segmentation rupture was only 10 years or so during active phase of earthquakes.Historical records show that seismic activities migrated distinctly from west to east along the MHT during last 1800 years,revealing that four seismic gaps,including the Hindukush,western Nepal.,Sikkim-Bhutan and India-Myanmar border area from west to east respectively along the MHT,occur in the Himalayan thrust belt,especially the last two gaps to the east of the 2015 Nepal earthquake vulnerable to geohazards.Collision between Indian plate and Eurasian plate is not only the driving force for deformation of present Chinese continent but the leading tectonic factor for frequent occurrence of strong earthquakes in China.Our study shows there is spatial-temporal relation of big seismic activities in Himalayas,QinghaiTibet plateau and adjacent areas,which are reflected by alternative occurrences of big earthquakes during active stages and vertical migration of big earthquakes perpendicular to the Himalayan orogenic belt.The previous seismic records in the Qinghai-Tibet plateau and adjacent areas and analysis results of future seismic geohazards reveal that during a next new round of seismic activity in the Himalayan seismic belt,Chinese mainland will likely face the sever situation of seismic hazard,especially the regional

关 键 词：2015年尼泊尔Ms8.1地震 喜马拉雅造山带 青藏高原 中国活动构造 地震危险性评价 

分 类 号：P315.2[天文地球—地震学]