青海玛多M_(S)7.4地震前b值时空变化特征  

Temporal and Spatial Variation of b-value before Maduo M_(S)7.4 Earthquake

作　　者：杜航[1] 杨云[1] 郑江蓉[1] 王俊[1] 张扬[1] 宫杰[1] Du Hang;Yang Yun;Zheng Jiangrong;Wang Jun;Zhang Yang;Gong Jie(Jiangsu Earthquake Agency,Nanjing 210014,China)

机构地区：[1]江苏省地震局,南京210014

出　　处：《震灾防御技术》2022年第4期691-700,共10页Technology for Earthquake Disaster Prevention

基　　金：江苏省地震局青年科学基金(202102);江苏省地震局科技创新团队(202204);地震预测开放基金(XH22033D)。

摘　　要：大量研究表明地震孕育过程中存在相对平静期,该阶段b值会相对下降,b值变化在地震活动性研究中起着十分重要的作用。2021年5月22日青海玛多发生M_(S)7.4地震,为研究地震前b值时空变化特征,本文截取2009年至震前地震目录,将地震目录分为去除余震目录、完整地震目录,对比研究b值变化特征。研究发现,玛多M_(S)7.4地震前1年b值开始低于均值且不断下降,至b值有上升趋势时地震发生,扩大到区域内其它5级以上地震,也符合此规律,地震发生后b值明显上升,短时间内又下降至较低位置,并一直处于较低位置直至下次地震发生;从b值空间扫描结果看,玛多M_(S)7.4地震前,震中位于低b值区域,该位置为b值最低处;通过不同时间段的b值空间扫描结果,可发现玛多M_(S)7.4地震发生前低b值区域向震中不断迁移,表明地震发生前震中附近应力不断集中;b值空间扫描时,完整地震目录掩盖了中强震震中区域低b值特性,去余震地震目录较好的凸显了中强震震中区域低b值特性。A large number of studies have shown that there is a corresponding quiet period in the gestation process of an earthquake,during which the b-value will decrease accordingly,and the change of b-value plays a very important role in the study of seismic activity.M_(S)7.4 earthquakes occurred in Maduo County,Qinghai Province on May 22,2021.To study the relationship between the spatiotemporal changes of b-value before the earthquake,the earthquake catalog from 2009 to before the earthquakesis extracted to study the changes of b-value in the earthquake focal area.The results show that the b-values of this earthquake in the focal area of earthquake with a magnitude of more than 5 decreased correspondingly about half a year before the earthquake,while the b-value rises suddenly and then decreases rapidly before the earthquake,and the earthquake mostly occurs in the descending stage.In this paper,short-term spatiotemporal scanning was carried out for two earthquakes above M5 in the focal area,and the epicenters were all located in low bvalue region.This study found that short-term changes in b-values seem to be related to earthquakes.The epicenters of moderate and strong earthquakes in the study area are all located in low b-value areas.Further research is needed to determine whether this feature is universal or not,and ultimately to find the best earthquake prediction method.

关 键 词：玛多M_(S)7.4地震 B值 时空扫描 地震目录 

分 类 号：P315[天文地球—地震学]