云南盐津2个地震序列震源参数测定及发震构造探讨  

Focal Parameters and Seismogenic Structure of Two Earthquake Sequences in Yanjin,Yunnan

作　　者：顾慧冬 姜金钟[1,2,3] 李姣 张演[1,3] 杨跃文[1] 王光明 张帅[1,3] 姚远 GU Huidong;JIANG Jinzhong;LI Jiao;ZHANG Yan;YANG Yuewen;WANG Guangming;ZHANG Shuai;YAO Yuan(Yunnan Earthquake Agency,Kunming 650224,Yunnan,China;School of Earth Sciences,Yunnan University,Kunming 650504,Yunnan,China;Kunming Institute of Prediction,China Earthquake Administration,Kunming 650224,Yunnan,China)

机构地区：[1]云南省地震局,云南昆明650224 [2]云南大学地球科学学院,云南昆明650504 [3]中国地震局昆明地震预报研究所,云南昆明650224

出　　处：《地震研究》2024年第3期391-404,共14页Journal of Seismological Research

基　　金：中国地震局地震科技星火计划项目(XH212502Y);云南省地震局科技专项(2021ZX04);云南省地震局传帮带项目(CQ3-2021003);中国地震局地震科技星火计划项目(XH21039Y);云南省地震局“地震机理与孕震环境研究”创新团队.

摘　　要：2021年1月23日云南盐津发生M L5.2地震,在此次地震前后该区域已经发生了多次中小地震。为了更好地评估该地区的地震危险性及识别发震构造,利用云南和四川地震台网的近震波形资料,采用CAP方法和2种速度模型反演了盐津M L≥3.5地震的震源机制解和震源深度,结合sPn深度震相测定了盐津M L5.2地震的震源深度,最后采用双差定位法对盐津地震序列进行重定位。结果表明:①最大震级为M L5.2的“孤立型”地震序列发震断层为逆断层,走向近SN向、倾向东、倾角约50°,是一次沿断层面自下而上破裂较为充分的浅源地震;②最大震级为M L3.9的“震群型”地震序列发震断层为走滑型断层,走向为NNW向、倾向北东、倾角约为80°,该序列内3次M L≥3.5地震的震源机制解略有差异,可能是由于该区域复杂的断层结构和应力环境影响所致;③最大震级为M L3.9的“震群型”地震序列的发震断层可能为盐津—筠连断裂,而最大震级为M L5.2的“孤立型”地震序列的发震断层可能为华蓥山断裂与盐津—筠连断裂共同作用产生的一条未知隐伏断裂。Before and after the M L5.2 earthquake in Yanjin,Yunnan Province on 23 January 2021,several medium and small earthquakes occurred in this region.In order to better assess the seismic hazard and identify the seismogenic structures in this region,we use the waveform data of the near earthquakes from the Yunnan Seismic Network and the Sichuan Seismic Network to invert the focal mechanisms and the depths of the M L≥3.5 earthquakes in Yanjin by the cut-and-paste(CAP)method and two different velocity models.Then,we determine the depth of the M L5.2 earthquake using the depth phase sPn.Finally,we employ the double-difference relocation method to relocate the earthquake sequences in Yanjin.We obtain that seismogenic fault of the isolated M L5.2 earthquake sequence belongs to the thrust type.It strikes near the N-S direction and dips eastward at 50°.The M L5.2 earthquake has a shallow source,the rupture occurred from the bottom to the top along the fault plane.The seismogenic fault of the swarm-type M L3.9 earthquake sequence belongs to the strike-slip type.It strikes from NNW and dips northeastward at about 80°.The focal mechanisms of the three M L≥3.5 earthquakes in this swarm-type sequence are slightly different,this may be due to the region s complex fault structure and stress environment.Based on this analysis,we believe that the seismogenic fault of the M L3.9 earthquake sequence is the Yanjin-Junlian fault.The seismogenic fault of the M L5.2 earthquake sequence is an unknown hidden fault in the near N-S direction and with a dip angle of about 50°,which is generated by the Huayingshan fault and the Yanjin-Junlian fault.

关 键 词：盐津地震序列 震源机制解 重定位 SPN震相 发震构造 

分 类 号：P315.332[天文地球—地震学]