图28  京、津、唐、张地区M_Ｌ≥3.0级地震震中分布图^［10］

Fig.28  Epicentral distribution of M_Ｌ≥3.0 earthquakes in Beijing-Tainjin-

        Zhangjiakou region

        (a) 1973.5-1976.6; (b) 1976.7-1977.12; (c) 1978.1-1980.12