初步认为荣成震群是一次频发性震群，不是前兆震群。
It is suggested that the swarm might occur frequently and was not a precursory one.
其他许多中国的大地震象海城地震一样，也有类似的前兆震群。
Many other violent earthquakes sofar occurred in China, similar to the Haicheng earthquake, also had precursory earthquake swarms.
应用主成分分析方法构建了前兆震群判别方程，对震群活动的异常特征进行了分析。
The anomalous characteristic of the swarm activity is analyzed using the precursor swarm distinguishing equation constructed by the principal component analysis method.
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