基于尼泊尔Mw7.8地震的喜马拉雅俯冲带滑坡分布规律研究  

Landslide distribution pattern in the Himalayan subduction zone based on Mw7.8 earthquake in Nepal

作　　者：刘亢[1,2] 李海兵[2] 李亦纲[1] 王金萍[1] LIU Kang;LI Haibing;LI Yigang;WANG Jinping(National Earthquake Response Support Service,Beijing,100049;Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing,100037)

机构地区：[1]中国地震应急搜救中心,北京100049 [2]自然资源部深地动力学重点实验室,中国地质科学院地质研究所,北京100037

出　　处：《地质学报》2019年第10期2666-2677,共12页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41631073和41502206)资助的成果

摘　　要：全球多数大地震发生在俯冲带地区,然而对于俯冲带地震诱发的滑坡研究并不多见。2015年4月25日尼泊尔廓尔喀县发生了Mw7.8地震,为喜马拉雅俯冲带近70年来的首次强震,震源机制解表明为低角度逆冲型的俯冲带地震,触发了大量滑坡、崩塌等地震次生灾害。通过遥感解译和现场调查获取2072组地震滑坡信息,揭示滑坡多数分布在海拔1000m^3000m之间,高喜马拉雅与低喜马拉雅的过渡区域,基本沿主中央逆冲断裂断裂(MCT)展布,地势落差大。早期断裂活动频繁,由中、高级变质岩和新生代浅色花岗岩变为古生代沉积岩和少量岩浆岩组成的逆冲岩席,易于发生滑坡、崩塌等地质灾害。滑坡坡度值优势分布区间为35°~40°,与中国西部地区一致,说明地震滑坡坡度分布与大的构造背景相关性较小,可能受局部地形地貌、地层岩性等因素控制。坡向值的优势分布区间为120°~200°,与水平形变场关系紧密。以尼泊尔地震滑坡为例探讨了喜马拉雅俯冲带地震滑坡的特征:滑坡点明显呈相对较宽的矩形区域展布,受深部逆冲推覆构造低倾角的断层破裂面影响较大,滑坡全部位于上盘,由于地震运动的惯性作用,在坡向与上盘逆冲方向一致的斜坡上容易诱发地震滑坡。Most the major earthquakes occur in subduction zones.However,there are few studies on earthquakeinduced landslides in subduction zones.On Apr.25,2015,an earthquake(Mw=7.8)hit Gorkha district,Nepal,which was the first strong earthquake in the Himalayan subduction zone in nearly 70years.Focal mechanism solution shows that it is a low-angle thrusting subduction zone earthquake and induced a large number of secondary disasters such as landslides and collapses.2072sets of seismic landslide information were obtained by remote sensing interpretation and field investigation.Seismic landslides are mainly distributed between 1000and 3000mabove sea level,in the transitional areas of the Higher Himalayas and the Lower Himalayas,spreading and distributing along the MCT,with large slopes in terrain.Paleozoic sedimentary rocks which are transformed from the medium-and high-grade metamorphic rocks,combine a small amount of magmatic rocks to form thrust sheets,and therefore the rock strata are liable to trigger geological?disasters such as landslides and collapses.The predominance range of slope values of the landslides in this earthquake is between 35°~40°,which is the same as the western region of China.The aspect values prominent distribution is between 120°~200°.In the light of the comprehensive GPS deformation field data,it reveals that the landslide aspect is closely related to the horizontal deformation field.Taking Nepal earthquake landslide as an example,the characteristics of earthquake landslide in subduction zone are discussed.The landslide points are apparently planar distribution and closely related to the deep low dip fault rupture plane.Earthquake-triggered landslides in the subduction zone are affected by the inertia effect of the plate movement.It is more likely to trigger seismic landslides on the slope which is in the same direction as the thrust direction on the hanging wall side.

关 键 词：喜马拉雅俯冲带 尼泊尔地震 滑坡 坡度 坡向 

分 类 号：P64[天文地球—地质矿产勘探]