四川芦山 MS7．0地震震源机制解

摘要

使用中国数字地震台网记录的区域和远震宽频带波形，通过频率域和时间域多步反演，研究四川芦山 MS 7．0地震基于点源模型的震源机制解和有限断层模型。考虑到使用不同波形资料类型、盆地效应及简化的一维速度模型等给反演震源参数带来的影响，经测试比较，结果表明：使用区域波形和本区域简化一维速度模型，波形拟合误差最小。此次地震表现为高倾角纯逆冲型事件矩心在水平方向上位于震中偏南西向约4．5 km，最佳波形拟合矩心深度约17 km，矩震级 MW约6．6。推断此地震大多数能量主要在震源偏南西约4．5 km 处释放。%We employ multistep inversions in the frequency or time domain,to infer the point-source and finite-fault model of Lushan MS 7.0 earthquake,mainly using regional and far broadband seismic waves recorded by the Chinese Digital Seismic Network.We take into account some factors,which could bring possible effects on the inverted result,consisting of different datasets,basin effect and simplified 1-D velocity models.The result indicates the misfit between observed waves and synthetics is better,if we use the regional waves and the 1-D velocity model in this studied area.This event occurs on a true rupture plane(strike=214°/dip=47°/rake=96°),showing a high-angle thrust faulting.The horizontal centroid locates at nearly 4.5 km southwest of the epicenter (30.303°N,102.988°E),and the best-fitting cen-troid depth is about 17 km.The total scalar moment M0 ,is retrieved with an average value of 1.16×10 19 N·m (or moment magnitude MW 6.6).We speculate that most of energy could release at nearly 4.5 km southwest of the epicenter.