2015年尼泊尔M_w7.8地震震源机制InSAR反演及强地面运动模拟  

Source parameters for the 2015 Nepal Earthquake revealed by InSAR observations and strong ground motion simulation

作　　者：李永生[1] 申文豪[1] 温扬茂[2] 张景发[1] 李振洪[3] 姜文亮[1,4] 罗毅[1] 

机构地区：[1]中国地震局地壳应力研究所(地壳动力学重点实验室),北京100085 [2]武汉大学测绘学院,武汉430079 [3]英国纽卡斯尔大学土木工程与地球科学学院 [4]中国地震局地质研究所,北京100029

出　　处：《地球物理学报》2016年第4期1359-1370,共12页Chinese Journal of Geophysics

基　　金：中央级公益性科研院所基本科研业务专项(ZDJ2015-15;ZDJ2013-22);国家自然科学基金(41374050;41204004;41204010)资助

摘　　要：2015年4月25日,在尼泊尔中部发生了Mw7.8地震.本文利用ALOS-2和SENTINEL-1A宽幅数据获取了该地震大范围的同震形变场,并反演了该地震断层破裂的几何特征及运动机制,继而以此为约束资料反演地震强地面运动.InSAR结果显示本次地震造成了巨大的地表形变,LOS向最大抬升量达到1.3m,最大下沉量达到0.7m.震源机制反演得到的最优的滑动分布模型表明,断层的走向为291°,倾角为7.6°,倾滑主要分布在深度为12～18km范围,主倾滑分布范围在长度上达到了140km,该范围内的平均倾滑角为95°.本次地震最大倾滑量达到5.3m,位于深度15km处.累计释放地震矩达6.5×10^20 N·m,约合矩震级Mw7.8.该地震发生在印度与欧亚板块俯冲逆冲界面之间,发震构造推断为主喜马拉雅逆冲断裂,属于典型的喜马拉雅型——低角度逆断层型强震.以该滑动分布模型参数为基础利用随机振动的有限断层模型进行尼泊尔地震的强地面运动模拟,结果显示最大地震烈度为Ⅸ度,烈度分布的范围及烈度等级与USGS模型结果对比具有很高的符合度.On April 25 2015,an Mw7.8earthquake occurred in Nepal,which is the largest since the 1934 Bihar Earthquake.2015 Nepal earthquake occurred in subduction thrust interface due to collision of Indian Plate and Eurasian Plate,which is the main seismogenic fault structure named Main Himalaya Thrust fault（MHT）.The earthquake released a huge amount of energy,causinghuge losses of people and infrastructure.Using a combination of ALOS-2ScanSAR wide mode data and SENTINEL-1AInterferometric Wide Swath data,we constructed maps of what happened on and below Earth′s surface during the Mw7.8earthquake in Nepal. Wide scan SAR data is very suitable for obtaining a wide range of deformation fields,especially for Nepal earthquake.The earthquake size is often described as slip over a larger fault area.The primarily model implies that the dimension of the fault is about120km×80km in size（length× width）.The conventional Strip Map mode with maximum100 km coverage is unable to obtain the complete deformation region of Nepal earthquake.In this paper,we use the ALOS-2and SENTINEL-1A wide scan data to obtain the wide coverage of the coseismic deformation field,then a two-step inversion strategy is employed to determine fault geometry and slip distribution,at last the seismic intensity surface motion is inverted from the distributed slip model.InSAR results show that the maximum uplift of～1.3mand the maximum subsidence of～0.7m,suggests that earthquake caused a huge ground deformation.The best-fit slip inversion model suggests that the major seismogenic fault is a thrust fault with a strike of～291°,a dip of～7.6°and an average rake angle of～95°.The slip is mainly distributed of 12～18km in the depth and of 140 km in length.The maximum amount of slip is up to 5.3min the depth of 15 km.The accumulative seismic moment was up to 6.5×10^20 N·m,equivalent to a magnitude of Mw7.8.On the basic of the distributed slip model,we use the finite stochastic fault model to simulate the strong ground motion of Nepal earthquake.The

关 键 词：尼泊尔地震 主喜马拉雅冲断裂 宽幅InSAR 强地面运动 

分 类 号：P237[天文地球—摄影测量与遥感] P313[天文地球—测绘科学与技术]