2022年3月17日甘肃肃南M_(S)5.1地震总结

Summary of the Sunan M_(S)5.1 earthquake in Gansu on March 17,2022

系统总结2022年3月17日甘肃肃南M_(S)5.1地震发生前的地震活动和地球物理观测异常,其中:①地震活动异常:震前存在地震成组活动异常;②地球物理观测异常:震中200 km范围内存在6项地球物理场异常,其中5项异常为趋势异常,但均非此次肃南M_(S)5.1地震的相关异常,而高台地震台形变异常虽为短期异常,但异常转折变化与本次地震无关;此外,肃南M_(S)5.1地震发生前,我国西北地区存在地磁低点位移、加卸载响应比和逐日比3项异常,但因后续于3月26日发生青海德令哈M_(S)6.0地震,认为该地磁预测指标对应成组地震活动,不能作为单一地震的震前异常。肃南M_(S)5.1地震余震较少,其序列活动特征显示为主余型;主震震源机制显示断层破裂为走滑型,与距离最近的疏勒南山断裂构造性质相符。综合分析认为,此次地震对于祁连山地震带及其周边后续中强地震的发生具有一定预测意义。

An earthquake with a magnitude of M_(S)5.1 occurred in Qilian Mountains on March 17,2022.The tectonic background,historical seismicity,geophysical observations,and sequence characteristics before the event are systematically summarized in this paper.The results show that:①Seismicity anomalies:there was one seismic activity anomaly along the Qilian Mountains seismic belt before the occurrence of the Sunan M_(S)5.1 earthquake;②Geophysical observations:measurements such as gravity,geomagnetism,water level,water temperature,fault hydrogen,and so on were available within 200 km of the epicenter of the Sunan earthquake,and most of the 6 anomalies before the event were long-term,but none of them are related to this Sunan M_(S)5.1 earthquake.Before the Sunan M_(S)5.1 earthquake,there were geomagnetic low-point displacement,daily variation amplitude ratio of geomagnetic observations,and geomagnetic load-unload response ratio anomalies.These phenomena point to a cluster of seismic activity,not only to this earthquake.This earthquake has a few aftershocks,and its seismic sequence activity characteristics show that this earthquake was a mainshock-aftershock type.The focal mechanism solution of the mainshock shows a strike-slip fault,which is similar to the Shule Nanshan fault.Meanwhile,the earthquake has certain significance for the prediction of the subsequent strong earthquakes in the Qilian Mountains seismic belt.