2021年11月17日江苏大丰海域M_(S)5.0地震总结  

About Dafeng sea area M_(S)5.0 earthquake in Jiangsu on Nov.17,2021

作　　者：黎明晓[1] 邓世广 马玉川[1] 解孟雨 王月 郭菲 LI Mingxiao;DENG Shiguang;MA Yuchuan;XIE Mengyu;WANG Yue;GUO Fei(China Earthquake Networks Center,Beijing 100045,China)

机构地区：[1]中国地震台网中心,北京100045

出　　处：《地震地磁观测与研究》2022年第4期148-159,共12页Seismological and Geomagnetic Observation and Research

基　　金：中国地震局震情跟踪(项目编号:2022020501)。

摘　　要：2021年11月17日江苏大丰海域M_(S)5.0地震发生在中强地震活动较为集中的黄海南部凹陷区,位于苏北—滨海断裂带附近,震源机制结果显示为走滑型破裂。截至2022年1月31日,发生M_(L)≥2.0余震14次,最大余震为2021年12月8日M_(S)3.8地震,主震释放能量占比约98.89%,判断地震序列应为主余型序列。主震发生3天后地震序列迅速衰减,因余震数量偏少,无法得到合理的序列参数。本次地震视应力值约1.3 MPa,基本处于研究区域正常背景水平。鉴于鲁东—黄海地块历史地震期幕活动特征,认为江苏及近海区域近期发生6级以上地震的可能性不大。系统梳理此次大丰海域M_(S)5.0地震前出现的地震活动和地球物理观测异常,可知:①地震活动:震前存在地震平静、霍山地震窗、长岛地震窗和地震空区等趋势异常;②地球物理观测:震前存在兴化水温异常。综合分析认为,此次地震发生前,地震活动异常相对较少,并以趋势异常为主,地球物理观测异常相对偏少,震前出现的流体短期异常现象可作为短期判定的参考依据。The M_(S)5.0 earthquake in Dafeng sea area occurred in the southern depression of the Yellow Sea,where M_(S)≥5.0 earthquakes are concentrated.It is located near the Subei-Binhai Fault Zone.The seismic focal mechanism result shows that it is a strike-slip fracture.Up to January 31,2022,there have been 14 aftershocks with M_(L)≥2.0,and the largest aftershock is the M_(L) 4.0(M_(S)3.8)earthquake on December 8,2021.The energy released by the main shock accounts for about 98.89%,and thus the type of this earthquake sequence is main shock-after shock type.Three days after the main shock,the sequence decays rapidly.Due to there are such few aftershocks in the sequence,we cannot obtain reliable sequence parameters.The apparent stress value of the earthquake is about 1.3 MPa,which is basically at the normal background level of the region.Based on the analysis of the episodic activity characteristics of historical earthquakes in the Ludong-Huanghai block,it is considered that there is little possibility of earthquakes with M_(S)≥6.0 in Jiangsu and offshore at present.The anomalies related to the Dafeng sea area M_(S)5.0 earthquake are comprehensively sorted out.In terms of seismicity,there were mid-term anomalies such as seismic quiescence(last until the earthquake),Huoshan seismic window,Changdao seismic window and seismic gap before the earthquake.The geophysical anomalies tracked before the earthquake are Xinghua water temperature anomalies.In one word,the anomalies before this earthquake are mainly mid-term anomalies,and the observed geophysical anomalies are relatively few and generally less than other M_(S)≥5.0 earthquakes.However,the increase of short-term fluid anomalies in this area can be taken as a reference for short-term judgment.

关 键 词：大丰海域M_(S)5.0地震 鲁东—黄海地块 地震活动异常 地球物理观测异常 

分 类 号：P315[天文地球—地震学]