2022年1月2日宁蒗M_(s)5.5地震异常特征分析

Analysis of Anomalous Characteristics Before Ninglang M_(s)5.5 Earthquake on January 2,2022

选取2022年1月2日宁蒗5.5级地震前距离震中250 km范围内的前兆资料,总结本次地震活动异常特征,并对比分析了距震中50 km范围内的两次历史5级地震前的异常特征,为今后该地区地震异常的判定及震情跟踪提供了参考。结果表明:宁蒗M_(S)5.5地震前共存在16项异常,其中测震学异常5条,微观前兆异常9条,宏观前兆异常2条,并在时间和空间上存在一定的特征。时间上,微观前兆异常以短期异常为主,震前3个月异常数量明显增加,表现为破年变和转折异常,地震活动性异常以中强地震长时间平静为主;空间上,微观前兆异常主要集中在震中200 km范围内,地震活动性异常主要为中小地震的有序条带分布。且与历史地震相比,此次地震与两次历史地震前的共有的异常特征有:宁蒗-木里-盐源多震区长时间中强震显著平静,在形变长趋势破年变异常背景下,流体短临异常较为突出。

In order to provide the reference for judging the destructive Ninglang earthquake anomaly and tracing the earthquake situation in the future,the characteristics of seismicity anomaly of the January 2th Ninglang M_(s)5.5 earthquake and the precursory data within 250 km from the epicenter are analyzed and summarized,and the anomalies before the two historical M≥>5 earthquakes within 50 km of the epicenter are compared and analyzed.The results show that there are 16 anomalies before the Ninglang M_(s)5.5 earthquake,including 5 seismicity anomalies,9 micro-precursory anomalies and 2 macro-precursory anomalies,and there are certain characteristics in time and space.In time,the micro-precursory anomalies are mainly short-term anomaly;the number of anomalies increases obviously 3 months before the earthquake;the anomalies are mainly annual variation change and transition;and the anomalies of seismicity are mainly long-term earthquake quiescence.In spacce,the micro-precursory anomalies are mainly concentrated within 200 km of the epicenter;and the seismicity anomalies are mainly distributed in bands of small earthquakes.The anomaly features common to the historical earthquakes are as follows:the Ninglang-Muli-Yanyuan multi-earthquake area has a long period of moderate and strong earthquakes that are remarkably calm,and the short imminent fluid anomaly is prominent under the background of the long trend of deformation breaking the annual variation anomaly.