利用近震波形研究2016年唐山M4.1地震震源参数及发震断层

基于首都圈地震台网观测数据,利用Hypo2000方法对2016-09-10河北唐山M4.1地震主震震中进行准确测定。采用近震波形反演方法,确定主震的最佳双力偶震源机制解为:节面Ⅰ走向122°、倾角60°、滑动角-42°;节面Ⅱ走向236°、倾角54°、滑动角-142°;矩震级约为M W4.3。结合近震深度震相sPL确定主震的震源深度约为6 km。使用双差定位法对余震进行重新精确定位,结果显示,余震深度集中分布在4~9 km,整体形态近于铅直,表明发震断层面具有倾向北西、倾角较陡的特点,与节面Ⅱ的性质较为一致,据此推测节面Ⅱ为发震断层面,节面Ⅰ为辅助面。将发震断层面参数与震源区附近断层性质进行对比分析认为,发震断层应为唐山断裂带中唐山-丰南断裂。

Research on Focal Parameters and Seismogenic Fault of the 2016 Tangshan M4.1 Earthquake Using Local Waveforms

Abstract: Based on the observation data recorded by Capital circle earthquake network, the mainshock epicenter of the 2016-09-10 Tangshan M4.1 earthquake is accurately determined by the Hypo2000 method. The best double-couple solution of the plane Ⅰ of the mainshock is 122°, 60°, and -42° for strike, dip, and rake angle respectively; the plane Ⅱ is 236°, 54°, and -142°; the moment magnitude is M_W4.3, which are analyzed by local waveforms inversion method. Combining with local earthquake depth phase sPL, the focal depth is determined as 6 km. The aftershocks are relocated by hypoDD, the results show that the focal depths are in the range of 4~9 km, distributed within a straight zone, indicating that the seismogenic fault should be a NE-trending fault with high dip, the characteristic of which is consistent with plane Ⅱ. We infer that plane Ⅱ is the seismogenic fault plane, and plane I is the auxiliary plane. Compared the parameters of the seismogenic fault with the properties of local faults, it shows that the seismogenic fault of Tangshan earthquake should be the Tangshan-Fengnan fault.