图13  大同-阳高6.1级地震前京西北-晋冀蒙交界地区震中分布图

（39°～42°N，111°～116°E，1985．1～1989．9，M_L ≥2．7）

Fig.13  Epicentral distribution of the events in the

        northwest area of Beijing-border land of Shanxi

        province，Hebei province and  Inner Mongolia before

        the M6.1 Datong-Yanggao earthquake