Abstract: Using rich history earthquake data, author studied some feature of strong earthquake activity in space and time variation in North China.The most remarkable characteristics of strong earthquake activity shows clearly the heterogeneity in time, which is represented by the active and calm period. On the basis of the heterogeneity of earthquake activity, strong earthquake activity since 1369 year can be divided into two active periods. According to release process of strain energy, each strong earthquake active period can be further divided into four stages of released strain energy.Spatial distribution pattern of strong earthquake activity in two active periods shows obviousl difference. These differences mainly are represented by large change of the pregnant environment and spatial distributive range of the large earthquake (M≥7). It is likely that the large change of the pregnant environment of large earthquake (M≥7) is very responsible for this obvious difference in the event time, total released strain energy, maximum magnitude of two active periods and so on.It is worthy to point out that strong earthquake active process of two active periods is not only very similar but also correlatable, Thus author will be able to judge the trend of strong earthquake activity.Finally author discussed possible reason of strong earthquake active difference of two active periods.

Key words: North China, Space and time variation for strong earthquake activity

摘要： 本文利用华北丰富的震史资料,分析该区强震活动时-空变化某些特点。并以此为依据,对近期强震活动趋势作出判断。文章最后部分还对华北地区最近两个活动期的强震活动水平的巨大差异的可能原因,从构造和介质条件等方面作些初浅讨论。

关键词: 华北, 强震时-空变化