图27 唐山7.8级地震前不同时段京、津、唐、渤地区地震震中分布图[15]
Fig.27 Epicentral distribution of _Beijing-Tainjin-Tangshan-Bohai earthquakes
in various periods before the M7.8 Tangshan earthquake
(a)1972.1-1973.2;(b)1973.3-6;(c)1973.7-1974.2;(d)1974.3-11;
(e)1974.12-1975.11.10; (f)1975.11.11-1976.7.27。
(图中虚线指[15]所示的围空)