华东地区地震前兆短期异常研究

通过对华东地区1970年以来发生的14次5级以上地震的研究表明:无论以异常开始时间判断的异常还是以异常结束时间(或转折时间)判断的异常,其空间分布与震前地震活动的空间分布存在一定关系,并且前兆异常存在不同特征的三阶段性。以前兆的开始时间作为判断标准,异常频次反映出地震孕育的中期阶段信息。以异常的转折(或结束)时间作为异常判断标准,其异常频度具有短期信息。从而提出了异常转折率TAR,研究表明,强震前TAR超过均值的高值异常具有短期信息。通过理论分析后,提出了华东地区中期向短期过渡的综合判断方法。

Study on short-term anomalies of earthquake precursors in the East China

This paper has mainly studied the 14 earthquakes with M>5 in the Eastern China since 1970s.The results show that,no matter the anomaly that is judged by anomaly start-time or that is by anomaly turning-ttime,there is a certain relation between the spatial distribution of precursors and seismicity before earthquakes,and 3-stages feature of different characteristics of precursor anomalies.If the start time of anomaly is taken as criterion,the frequency of precursor anomalies reflects the middle-term information of seismic generating process.If the time of turning point or ending time of the deformation abnormities is taken as the judge criterion,the frequency of precursor abnormities reflects the short-term information.Based on the above-mentioned study,we develop a method named the anomaly-turning ratio(TAR).The results show that,the high-value anomaly of the TAR exceeding mean value may reflect the short-term information.By theoretical analysis,we provide a comprehensive method to judge the variety from middle-term anomaly to short-term one in the Eastern China.