大姚、民乐-山丹地震前的中短期前兆  

MEDIUM AND SHORT-TERM PRECURSORS OF FAULT DEFORMATION BEFORE DAYAO AND MINLE-SHANDAN EARTHQUAKES

作　　者：张希[1] 薛富平[1] 王双绪[1] 

机构地区：[1]中国地震局第二监测中心,西安710054

出　　处：《大地测量与地球动力学》2004年第4期57-63,共7页Journal of Geodesy and Geodynamics

基　　金：国家重点项目:"中国大陆构造变形变化特征和重点地区应变积累状态研究";地震科学联合基金:"地壳运动的非震负位错模型反演与强震地点预测研究";中国地震局"十五"项目子课题:"青藏高原北部地区地震活动短期前兆特征及其预测方法研究"

摘　　要：利用川滇及青藏块体北缘地区上世纪 80年代至 2 0 0 3年的跨断层流动形变观测资料 ,借助应变强度比时序曲线 ,通过丽江Ms7.0、景泰Ms5 .9等震例研究 ,获取与 2 0 0 3年 7月大姚Ms6 .2、Ms6 .1地震和 10月民乐 山丹Ms6 .1地震孕育有关的中短期前兆异常。分析表明 :①大姚、民乐 山丹地震前 1年内异常场地数远超过场地总数的 1/ 3,相对近源区异常在发震地区占一半 ;②大姚Ms6 .2地震前半年内 ,盐源 丽江地块及其邻近区域以及北东向延伸的川滇交界地区异常明显增多 ,相对集中。 2 0 0 3年 7～ 9月大幅减弱 ;而鲜水河断裂、楚雄 通海断裂南段有所增强 ;③民乐 山丹震前十余天至数月内相对近源区及其邻近构造区域呈现异常相对分散 相对集中且局部增强 临震前减弱的时空演变特征。震后一个月内青藏块体北缘地区仍有近 1/ 3的场地呈现异常 (海原 六盘山断裂带尤为突出 )。Using mobile observations of deformation of cross-faults from the 1980s to 2003 in Sichuan-Yunnan area and the northern margin of Qinghai-Tibet block, by means of the time-curve of strain intensity ratio and analyses the seismic examples such as the Lijiang %M%s7.0 and the Jingtai %M%s5.9,the medium and short-term of precursory anomalies related to the Daoyao Ms6.2,Ms6.1 and Minle-Shandan Ms6.1 earthquakes which took place respectively on July and October of 2003 are studied. It is shown that: ①The number of sites with anomaly for one year before the Daoyao and Minle-Shandan earthquakes was much more than 1/3 of total, and the number of sites with anomaly in the region nearby the epicenter was half of that in the area where the earthquakes took place. ②In six months,before Daoyao earthquake, Yanyuan-Lijiang block and its nearby, together with its expanding northeastward to the boundary between Sichuan and Yunnan,the precursory anomalies increased remarkably and concentrated relatiely. Furthermore, from July to September of 2003, the precursory anomalies became weak obviously in this region, but stronger in the Xianshuihe fault and the southern segment of Chuxiong-Tonghai fault. ③From dozen days to serveal months before the Minle-Shandan earthquake in the region near the epicenter the time-space evolution features of deformation anomalies manifest themselves from relatively sparse to relatively concentrated and anomalies with locally enhanced to decreased.In a month after the earthquake, nearly 1/3 of sites revealed abnormal deformation(especially Haiyuan-Liupanshan fracture belt).

关 键 词：民乐-山丹地震 青藏块体 异常 源区 前兆 地震孕育 震例 短期 时序 曲线 

分 类 号：P315[天文地球—地震学] P316.242[天文地球—固体地球物理学]