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Title:: Retrospective Analysis of Seismometric Anomalies before the 2021 Yangbi,Yunnan M_S6.4 Earthquake

Author(s):: LIU Zifeng; SUN Nan; WANG Guangming; PENG Guanling; LI Yongli; ZHANG Tianyu; MAO Huiling; ZHAO Xiaoyan; (Yunnan Earthquake Agency,Kunming 650224,Yunnan,China)

Keywords:: seismometric anomalies; focal mechanism consistency; seismic belt; intensified earthquake activities; foreshock sequence; the Yangbi M_S6.4 earthquake

摘要:: 为了完善云南地区测震学预测指标体系,对2021年云南漾濞M_S6.4地震前平静类、增强类、条带类、参数类测震学异常和前震活动特征进行回顾总结,得到以下主要认识:①地震前测震学异常以不同时空尺度、不同震级档地震的平静为主,条带交汇现象也十分显著,震中附近震源机制趋于一致,2012—2017年滇西北地区5级地震丛集发生,且自2020年以来小滇西及邻区4级地震出现增强活动,以中长期异常为主,临震阶段震源区中小地震密集发生构成前震。②根据震前提出的测震学异常做出的中长期、较大区域的震情趋势判定是正确的,但临震前的前震识别工作因过多依赖以往震例经验而存在不足。

Abstract:: In order to improve the seismometric prediction index system in Yunnan,we review the seismometric anomalies which we had tracked and analyzed before the 2021 Yangbi M_S6.4 earthquake,including earthquake quiescence,intensified earthquake activity,earthquake strips,seismic parameters,and the characteristics of the foreshocks' activity.Then we draw the following conclusions:①the seismometric anomalies before the Yangbi earthquake contained mainly the quiescence of earthquakes in different periods and spaces and of different magnitudes.The earthquake strips intersected significantly.A cluster of 5-magnitude earthquakes occurred in northwestern Yunnan from 2012 to 2017,and the activity of 4-magnitude earthquakes intensified in the sub-region of western Yunnan and its neighboring regions since 2020.The anomaly of the activity of foreshocks mainly featured as in medium-and long-term.The small-and medium-foreshocks intensively occurred in the source area of the Yangbi earthquake.②Our judgment on the seismic tendency in middle-and long-term and in large area in West Yunnan based on the seismometric anomalies we put forward before the Yangbi earthquake is correct.However,as we depend much on the experience of the past earthquake cases,our identification of the impending foreshocks before the Yangbi earthquake has some disadvantages.