强震前形变异常的时空演化特征  

The temporal-spatial evolution characteristics of deformation anomaly before strong earthquakes

作　　者：宋先月[1] 宋治平[1] 武安绪[2] 薛艳[3] 倪友忠[1] 

机构地区：[1]上海市地震局,上海200062 [2]北京市地震局,北京100081 [3]中国地震局分析预报中心,北京100036

出　　处：《地震》2003年第2期70-76,共7页Earthquake

基　　金："十五"国家科技攻关项目(2001BA601B01-O4-02);地震科学联合基金(101105)

摘　　要：主要对华北北部地区的1989年大同地震、1991年大同地震及1998年张北地震3次强震前的形变异常时空演化特征进行了研究。结果表明,若以形变异常的开始时间作为判断标准,形变异常的群体频次在强震前1～2年内均出现高于或接近2倍均方差的高值状态,显示出形变异常的中期异常,异常时空演化的三阶段特征表现不明显。若以形变异常的转折时间(或结束时间)作为异常判断标准,形变异常频次在震前1～4个月达到高值,显示出异常的短临信息,并且,形变异常的时空演化过程存在明显的三阶段(α、β、γ)特征。在对这些特征进行理论分析的基础上,提出了将形变异常的开始时间与转折时间分别作为判断标准,如果两种群体频次均处于异常状态,则表明异常已处于从中期向短期过渡的阶段,反之,异常仍处于中期阶段。这种形变异常的分析思路可作为形变异常从中期阶段向短期阶段过渡的一种判断方法。This paper mainly discusses the temporal-spatial evolution characteristics of deformation anomaly before the Datong earthquakes in 1989, 1991 and the Zhangbei earthquake in 1998. The results show that, if the start time of anomaly is taken as a judgment criterion, the frequency of deformation anomaly is usually higher than or near twice mean square deviation during 1-2 years before strong earthquakes. That is, this shows the mid-term anomaly of deformation, which the 3-stages characteristics in the temporal-spatial evolution process are not obvious. If the time of turning point or end time of the deformation anomaly is taken as the judgment criterion, the frequency of deformation anomaly will come to the maximum value 1 ~ 4 months before the earthquakes. This shows the short-term information and obvious 3-stages characteristics (a,B,). Based on the theoretical analysis of these features, the starting time and the time of turning point may be taken as the judgment criterion respectively. If the frequencies obtained by two methods are all anomalous, it indicates the anomaly is in the transitional stage from mid-term to the short-term. Otherwise, it is in the mid-term stage. This analytical idea can be used to judge the transitional stage from mid-term to the short-term of deformation anomaly.

关 键 词：华北地区 大同地震 1991年 张北地震 强震 地震前兆 地壳形变 

分 类 号：P315.725[天文地球—地震学]