2013年4月20日四川芦山MS7.0地震:一个高角度逆冲地震

利用中国地震台网和IRIS数据中心提供的近远震数字地震波形记录,首先读取P波初动方向,在考虑深度误差和速度模型引起的离源矢量误差基础上,利用网格搜索方法,计算了2013年4月20日四川芦山M_S7.0地震断层面解,其断层面走向/倾角/滑动角依次为212°/44°/92°.然后采用近远震波形联合反演方法(CAPjoint),反演了地震矩心深度和点源近似下双力偶解,表明地震发生在12 km深度,发震断层面参数为212°/47°/93°.通过分析波形反演中深度和震源区地震波速度模型对断层面倾角的影响,并结合短期余震机制解,认为芦山M_S7.0地震是一个高角度逆冲地震.

The Lushan Ms7.0 earthquake on 20 April 2013: A high-angle thrust event

P wave first motions picked from regional and teleseismic records were used to invert focal mechanism of the Lushan M_S7.0 earthquake on 20 April 2013. To reduce errors introduced by uncertainties of take-off angle due to the velocity model and focal depth errors, random perturbations of take-off angle were added into raw values. After multiple trials, strike/dip/rake angles of the best solution are calculated to be 212°/44°/92°. To better understand focal mechanism, the regional and teleseismic waveforms inversion method (CAPjoint) was employed to determine the centroid depth, double-couple solution and magnitude. The results (212°/47°/93°, depth=12 km, M_w6.7) suggest that the Lushan earthquake is a high-angle thrust event. Both inversion results with three other seismic velocity models and focal mechanisms of short term aftershocks support this solution.