Abstract: In this paper, the earthquake activity of the 3rd and 4th active periods in North China region since the 20th century has been comprehensively analyzed. The authors have found that there are different space distributionty pes of earthquake activity during the previous and following active periods, but the two earthquake activity periods are closely connected each other and are independent. By compari son, the main body areas of the earthquake activities in the two earthquake activity periods show the characteristics without repeatability basically and the same intervals between the earthquakes. The authors think that this feature will be important to study and analyze the location of earthquakes in the future.

Key words: North China region, Seismicity feature, Spatial evolution