华东地区具有短期预测意义的特殊显著性地震事件识别

依据华东地区中强地震前的地震活动特点,初步提出“特殊显著性地震事件”SPE的概念及其可能的识别方法.具有前兆指示意义的SPE可划分为三类，三类SPE分别表达了主震前中小地震与主震之间的时空位置关系.I类SPE距主震时、空距离均较近，在一定程度上与“直接前震”具有相似之处；II类SPE距主震时间较近、而空间距离可能较远，但与主震之间有一定的构造联系，具有时间上的“信号地震”的意义.Ⅲ类必须首先通过地震活动性方法对可能的SPE进行筛选，之后通过比较其与之前在同一位置发生的一系列中小地震的地震波参数之间的差异，在一定程度上进一步确认其短期预测意义.华东6次中强地震震例的研究结果表明，当可能的SPE的单台波速比小于此前该区域长时期的均值、归一化尾波持续时间大于此前该区域长时期的均值以及振幅衰减系数与此前该区域长时期均值之差大于长时期均值的30％时，可进一步认定其短期前兆意义.

Identifing special precursory earthquake events with forecasting significance in east China

According to the features of seismic activity before the moderate-strong earthquake in north east China, an identifing method on special precursory earthquake event(SEP) is tentatively proposed. The SPE with precursory significance can be divided as three types. The type Ⅰ SPE is near the mainshock in time and space. The thpe Ⅱ SEP is near in time but far in space with the mainshock. The type Ⅲ SPE is near the mainshock in space but the time duration from SPE to mainshock is long. The potential SPE should be filtered firstly by the normal seismic activity methods, and then the difference of seismic wave parameters between the SPE and small earthquakes occurred in the same site and before should been compared., Results from 6 moderate-strong earthquakes in north east China show that the short forecasting significance of SPE could be more affirmed when three conditions be satisfied: (1) vp/vs of the SPE is smaller than average value during a long period; (2) normalized duration of trail wave of SPE is larger than average value during a long period; (3) attenuation coefficient of wave amplitude of SPE is about 30% larger than average value during a long period.