2016年1月21日青海门源Ms6.4地震震源机制解及发震构造初步探讨

Preliminary Discussion on the Focal Mechanism Solutions and Seismogenic Structure of Menyuan Ms6.4Earthquake on Jan.21,2016in Qinghai

采用CAP(Cut and Paste)方法反演了2016年1月21日青海门源MS6.4地震的震源机制解,其最佳双力偶解节面I走向339°,倾角49°,滑动角111°:节面Ⅱ走向129°,倾角45°,滑动角68°,矩震级MW5.92,矩心震源深度约为9km,地震破裂类型为逆冲型地震。结合余震序列展布及震区的活动构造特征,判定发震断层面为节面I,推测此次地震的发震断裂为冷龙岭断裂。

According to Chinese seismological station net determination,aMS6.4earthquake occurred at 01：13,Beijing time on Jan.21,2016 in Menyuan county of Qinghai province.By the end of Feb.11,475 aftershocks of ML≥ 1.0had occurred in the seismic region of the Menyuan6.4earthquake,including 4.0~4.9level 1and 3.0~3.9level 17 times.The largest magnitude of ML4.4occurred at 01：18on Jan 21,and the Menyuan earthquake caused heavy economic losses.The CAP method is one entire profile inversion method,its inversion result has an advantages of relatively small merit which relies on the speed model and the earth＇s crust lateral change.The core idea is as follows：we split the seismic broadband waveform data into Pnl and surface wave parts,calculate the objective error function of the observed and the theoretical seismograms,perform the grid search in the assigned parameter space,and search the focal mechanism and the focal centroid depth of the two global minimum variances.In the paper,using the wave data from＂the fifth＂Seismological Network of Gansu province and Qinghai province,we adopted the CAP method to obtain the focal mechanism of the 6.4earthquake occurred at Menyuan on Jan.21,2016.The results show that the focal character of the earthquake is thrust,MW5.9and the focal depth of the event is 9km.The nodal plane I parameters of the best double-couple are strike339°,dip 49°,and rake 111°,respectively.The strike of the nodal plane is the same trend with the strike of the Lenglongling fault;the characteristics of the dip are according to the properties of the Lenglongling fault.The nodal plane has been identified to be representative of the seismogenic fault plane.Analysis considers that the occurrence of Menyuan 6.4earthquake has osculating correlation with the activity of the fault.