摘要
利用日本ALOS-2和欧空局Sentinel-1A卫星获得的尼泊尔地震同震形变场,结合GPS同震位移数据,联合反演了断层滑动分布特征和空间展布.结果表明：尼泊尔地震的同震形变场主要集中在150km×100km的范围内,且分为南北两个相邻的形变中心,南形变中心的视线向抬升量约为1.2m,北形变中心的视线向沉降量约为0.8m,均位于发震断层上盘.位于形变抬升区的KKN4和NAST两个GPS站,抬升量和南向运动量均达到了m级,而远离震区的其他GPS台水平和垂直观测量均在1cm以内.联合反演得到的断层位错分布主要集中在沿走向150km,沿倾向70km的范围内,最大滑动量为5.59m,平均滑动量为0.94m.断层面倾角在浅部约为7°,随着深度增加,倾角逐渐变大,到垂直深度20km时倾角接近12°;5月12日MW7.2级余震位于主震破裂区的＂凹＂型滑动缺损区域;主震破裂区的上边界与MBT空间位置十分吻合,主震破裂区主要集中的MBT以北50~60km处,垂直深度为8~9km,倾角为9°,继续向北时主震破裂面以10°~12°的倾角向深延伸,在18~20km可能与MHT交汇.因此,初步判定MBT为此次地震的发震断层.
An MW7.9earthquake,located at the front of the India-Eurasia collision belt,struck Nepal on April 25 th,2015.Focal mechanisms from different organizations show a dip angle of7°~10°,which indicate a typical Himalayan-type low-angle thrusting earthquake.Almost no surface ruptures were found after the earthquake,making it difficult to interpret the spatial characteristicof the coseismic slip distribution,and most importantly,the possible causative fault buried underneath the sub-surface.We seek to answer these questions by joint inversion of InSAR coseismic deformation observed by ALOS-2and Sentinel-1ASAR satellites,as well as some GPS measurements.The method of joint inversion was used to analyze the spatial characteristic of the coseismic slip distribution and to infer the possible causative source fault of the 2015 Nepal earthquake.We collected the Sentinel-1A data immediately after the mainshock and processed them using the GAMMA software.Besides,the relevant ALOS-2and GPS data were also collected.The quadtree sampling method was then used to resample the InSAR deformation results.In order to obtain a robust result and to reduce the uncertainties of the inversion,initial parameters for the fault were assigned according to focal mechanisms from Global CMT,USGS and GFZ.（1）The coseismic deformation field derived from geodetic data shows that the Nepal MW7.9event is mainly distributed within a 150 km long and 100 km wide range,with two peak deformation centers aligned close to each other in north-south direction reaching about 1.2m and about0.8m,respectively,and both of which are located on the hanging wall side,demonstrating a low-angle thrust.The InSAR results confirm that the surface trace of the causative source fault coincides with the MBT.Two GPS stations,namely KKN4 and NAST,about 80 km away from the epicenter on the hanging wall side,have peak displacements over 1 m.However,GPS stations at the far field decay very rapidly,which only have about 1cm of coseismic displacements in both horizontal and verti
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2015年第11期4266-4276,共11页
Chinese Journal of Geophysics
基金
国家自然科学基金(41461164002
41541031)
地震动力学国家重点实验室自主研究课题(LED2013A02)联合资助
