STUDY ON SEISMIC ACTIVITY CHARACTER OF MEDIUM-SMALL EARTHQUAKE IN THE JUNCTURE AREA OF SHANXI,HEBEI AND INNER MONGOLIA

The juncture area of Shanxi,Hebei and Inner Mongolia has experienced medium-strong earthquakes quiet period for ten years since the 1998 Zhangbei M_S6.2 earthquake.Based on this background, this paper uses the medium-small earthquake date from 1970 to 2013 to analyze the activities of mediumsmall earthquakes in the juncture area of Shanxi,Hebei and Inner Mongolia.It is found that 2 years before the 1989 Datong-Yanggao M_s5.9 earthquake,the 1998 Zhangbei M_S6.2 earthquake and the 2010 Datong M_S4.6 earthquake,in the epicenter of 3°×3°range,the month frequency of medium-small earthquake activities show obviously the process of increasing-attenuating-main earthquake occurring.This may be predictive meaning phenomenon has certain reference value to the strong earthquake prediction in the area.