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Title:: Focal Mechanism and Focal Depth Determination of Yunnan Yangbi M_S5.1 and M_S4.8 Earthquakes in 2017

作者:: 潘睿¹; 姜金钟^2; 付虹²; 李姣²; (1.云南大学资源环境与地球科学学院,云南昆明 650504; 2.云南省地震局,云南昆明 650224)

Author(s):: PAN Rui¹; JIANG Jinzhong²; FU Hong²; LI Jiao²; (1.Colledge of Resources,Environment and Geosciences,Yunnan University,Kunming 650504,Yunnan,China)(2. Yunnan Earthquake Agency,Kunming 650224,Yunnan,China)

关键词:: 漾濞地震; CAP方法; sPn深度震相; 震源机制解; 震源深度

Keywords:: Yangbi earthquake; CAP method; sPn depth-phase; focal mechanism; focal depth

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摘要:: 鉴于国内外地震研究机构给出的2017年云南漾濞M_S4.8和M_S5.1这2次地震的震源深度存在较大差异,利用云南和部分四川地震台网宽频带数字地震波形资料,采用CAP方法和3种不同速度模型对这2次地震进行震源机制解反演,并结合sPn深度震相对其震源深度进行了再次测定。结果表明:①由于利用了台站方位覆盖更好的近震宽频带波形和sPn深度震相数据,最终获得了2次地震的震源深度(5 km和6 km); ②基于更多台站记录的宽频带波形,利用CAP方法得到的双力偶震源机制解与Global CMT利用全球宽频带台站记录波形得到的反演结果更为一致,并且利用CAP方法得到5次M≥ 3.0余震事件的震源机制解与这2次地震的结果基本一致,表明这些地震事件可能发生于同一断层; ③经初步分析认为,2017年漾濞地震的发震断层可能是维西—乔后断裂中南段,即节面Ⅱ(312°/80°/166°)为真正的发震断层面。

Abstract:: Since different earthquake research institutes provided different focal depths of the Yunnan Yangbi M_S5.1 and M_S4.8 earthquakes occurring on Mar.27,2017,we refine the focal depths and focal mechanisms of these two earthquakes by using the broadband earthquake waveforms recorded by Yunnan Seismic Networks and Sichuan Seismic Networks in Cut-and-Paste(CAP)inversions with three different velocity models. We also employ the sPn depth-phase to double-check the focal depths of the Yangbi M_S5.1 and M_S4.8 earthquakes. The results are as follows:①Owing to we used the broadband waveform of near-earthquakes with better azimuth coverage and the phase data of sPn depth,the obtained focal depths of the two earthquakes(5 km and 6 km)are more reliable. ②Based on the broadband waveforms recorded by more stations,the double-couple focal mechanisms we obtained from CAP inversions are consistent with the focal mechanisms provided by both the Global Centroid-Moment-Tensor(GCMT),but slightly better than the focal mechanism solution given by the Institute of Geophysics,China Earthquake Administration(CEA-IGP)based on limited stations on the day after the earthquake occurred. The focal mechanism solutions of five M≥ 3.0 aftershocks obtained by CAP method are basically consistent with that of the two earthquakes,which indicated that these earthquakes may occur in the same fault. ③According to the DD relocation results and distribution of the quaternary active faults in Yunnan area,we preliminarily infer that the middle-south segment of the Weixi-Qiaohou fault,i. e. the plane II(312°/80°/166°)could be the seismogenic fault of the 2017 Yangbi M_S5.1 and M_S4.8 earthquakes.

《地震研究》[ISSN:1000-0666/CN:53-1062/P]

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