2015年尼泊尔M_w7.9地震破裂过程:快速反演与初步联合反演  

Rupture process of the 2015 Nepal M_w7.9 earthquake:Fast inversion and preliminary joint inversion

作　　者：张勇[1] 许力生[2] 陈运泰[1,2] 

机构地区：[1]北京大学地球与空间科学学院,北京100871 [2]中国地震局地球物理研究所,北京100081

出　　处：《地球物理学报》2015年第5期1804-1811,共8页Chinese Journal of Geophysics

基　　金：国家自然科学基金(41474046;41090291);地震行业基金(201108002)资助

摘　　要：本文介绍了2015年4月25日尼泊尔Mw7.9(MS8.1)地震发生后的破裂过程快速反演工作,以及后续开展的地震波与少量GPS资料的初步联合反演工作.两项工作得到的反演结果尽管在最大滑动量估计方面存在一些差别,但都一致地显示此次地震是发生在低倾角俯冲断裂上的一次单侧破裂事件,破裂主要朝东南方向传播;断层滑动主要发生在震中至加德满都一带.在加德满都附近区域,其下方破裂与朝东南传播的地震波的多普勒聚焦效应可能造成较强的震感和较大的破坏.对比历史大地震发现,2015年尼泊尔Mw7.9地震的浅部破裂紧邻1934年Mw8.2地震的地表破裂,余震分布与1833年M7.6地震的宏观震中基本重合,其破裂填补了前两次地震破裂以西100km左右的空区,表明此次地震是1934年Mw8.2地震与1833年M7.6地震向西继续延伸的结果.As a routine work for earthquake emergency response,we have performed fast inversions of rupture processes for large earthquakes since the 2008 Wenchuan Mw7.9earthquake.About 2.15 hours after the 2015 Nepal Mw7.9earthquake,we determined the rupture model by inverting teleseismic P waves.From the obtained rupture images,the earthquake was a unilateral rupture event and ruptures mainly propagated to the southeast.So we concluded that the earthquake may cause relatively terrible damages around Kathmandu area due to nearby ruptures and Doppler effects of the southeastward rupture propagations.After the fast inversion,we collected more seismic data and a few GPS data（two stations）,and carried out a joint inversion of rupture process.The joint model well confirms the major source characteristics,e.g.southeastward rupture propagation,and displays a larger peak slip（about 5.2m）than that of the fast estimated model（about 2.0m）.The source duration is about80 s,with the major sub-event occurred at 0～45s.At 60～70s,a small-scale sub-event occurs in very shallow depth about 100 km along the strike direction,and may cause a few surface breakages.From comparisons with historical large earthquakes,the 2015 Nepal Mw7.9earthquake ruptured an area,with a dimension of about 100 km,to the west of the 1833 M7.6earthquake and the 1934 Mw8.2earthquake.The shallow ruptures are very close to the surface ruptures of the 1934 Mw8.2earthquake,and the aftershocks are around the macroseismic epicenter of the1833 M7.6 earthquake.It is highly probable that ruptures of the three earthquakes have connected.From this perspective,the 2015 Nepal earthquake is the result of the westward rupture extensions of the 1833 and 1934events.

关 键 词：波形反演 破裂过程 2015尼泊尔地震 

分 类 号：P315[天文地球—地震学]