本文用修改了的系统聚类法研究华北地区地震活动期,结果表明,当类间距离用离差平方和增量距离,且样品间用欧氏距离时,能较好地划分该地区的地震活动期。而样品间用相似系数时,不论类间距离是哪一种,所得结果均较差。本文还作了地震活动期的后验预测尝试,还通过逐次筛选方法对21个特征进行了选择。 In this paper, the modified system clustering method is used to study the seismicity in North China. The results show that the earthquakes in this area can be well divided when the distances between the two classes are separated by the square of the sum of the deviations and the Euclidean distance between the samples Active period. When using similar coefficients between samples, no matter what kind of distance between classes, the results are poor. In this paper, posterior predictions of seismogenic period have also been made, and 21 features have been selected by successive screening methods.