九江-瑞昌5.7级地震前地震活动异常研究

选择反映地震活动时、空、强特征的8个地震活动性参数，即地震频次N(M _L≥2.0)、b值、η值、A(b)值、Mf值、Ac值、C值、D值，用因子分析法对2005年11月26日九江 瑞昌5.7级地震前活动异常特征进行研究，得到反映地震活动时、空、强异常特征的综合指标W _fa、主要影响因子及参数之间的相关关系。结果表明前4个因子的累积贡献率达95.14%，即主影响因子数为4个，其贡献率分别为50.53%、23.50%、16.79%和4.33%。

RESEARCH ON ANOMALOUS SEISMICITY BEFORE JIUJIANG-RUICHANG EARTHQUAKE

There were 8 seismic parameters i.e. earthquake frequencyN(ML≥2.0),b-value,η-value,A(b)-value,Mf-value,Ac-value,C-value and D-value be used to reflect seismic activity characteristics in time, space and magnitude. Applying the factor analysis method variations of all these parameters since 1980 were studied before the Jiujiang M5.7 earthquake occurred on Nov.26,2005 in Jiangxi province and the synthetic parameter W _fa value,major effective factors and certain correlation among these parameters were picked out.It showed that the camulative contribution rate of the four former factors reached to 95.14% totally. Being the four major effect factors,their contribution rate were 50.53%,23.50%,16.79% and 4.33% respectively.