基于强震记录快速确定康定地震的震源破裂方向研究

Rapid Rupture Direction Estimation of Kangding Earthquake Using Strong-Motion Recordings

2014年11月22日四川省康定县发生Ms6．3级地震，主震3d后发生Ms5．8级余震．为研究两次地震震源破裂特性并探讨通过强震记录快速确定震源破裂方向的方法，利用强震记录并基于网格搜索方法，快速确定了使强震动峰值参数预测值与震源方向性系数修正的观测值误差最小的震源破裂参数．研究结果表明：由于Ms6．3级地震震中西北方向强震台站缺失致其记录空间分布严重不均匀，确定的震源破裂方向不理想；对于Ms5．8级余震，结合流动台站的强震记录，快速确定了震源为双向破裂，主破裂方向约为北偏东320°，与断层走向及余震分布较为一致，主破裂方向上的破裂占整个震源破裂的70％-90％，破裂速度约为2．5～2．8km／s．

An Ms6.3 earthquake hit the Kangding County, Sichuan Province on November 22, 2014. Three days later, an Ms5.8 aftershock occurred. The source rupture properties of two earthquakes were analyzed and the method for rapidly estimating the source rupture direction was investigated using strong-motion recordings. The grid-search technique was used to seek the optimal source rupture parameters, including the predominant rupture direction and the rupture velocity, which can satisfy the minimum fitting error between the predicted peak ground-motion parameters and the observed ones corrected by the directivity coefficient. The results indicate owing to lack of the strong-motion stations in the northwest of the Ms6.3 earthquake epicenter, the non-uniform spatial distribution of the strong- motion recordings results in the bad estimation of the rupture direction. With strong-motion recordings from temporary strong-motion stations, the rupture parameters for the Ms5.8 earthquake were well estimated. The Ms5.8 earthquake predominantly ruptured in the N320°E direction, accounting for 70% -90% of the total rupture, which is consistent with the fault trend and the aftershock distribution. The rupture velocity of the Ms5.8 earthquake is approximately 2.5 -2.8 km/s.