群震（又称群发性地震、频发性地震）意指某处在相对而言较短的一段时间中发生一系列地震而无法明确判断出主震的地震型态。群震是火山喷发前会发生的典型地质活动之一。
另外一个震群于二月末三月初发生在都江堰和彭州之间。
Then there was another swarm at the end of February and early March between Dujiangyan and Pengzhou.
五原震群地震波形改变可能是由于地下介质流体成分增多柔性增强，由脆性向柔性过渡的原因。
The reason why seismic wave forms of Wuyuan swarm change might be transition of underground medium from brittleness to flexibility that increases duo to increase of fluid component.
它由三步组成：余震和震群的剔除，相对完全性的识别以及绝对完全性的计算。
It consists of three steps: removal of aftershock and swarm, detection of the relative completeness and evaluation of the absolute completeness.
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