强震前区域地震活动时常会出现一个平静或“缺震”过程 ,这种现象早已为国内外许多地震学者所关注 (陆远忠等 ,1 985 ;Wesson,1 973 ) .近十几年来我国地震工作者从不同角度对某些特定地区 ,对地震活动平静异常进行了专门研究 .蒋淳和冯德益 (1 989)以华北地区每年 5级地震的折 A serene or “missing earthquake” process often occurs in the seismic activity before the strong earthquakes, a phenomenon that has long been of concern to many seismologists both at home and abroad (Lu Yuanzhong et al., 1985; Wesson, 1973). In recent decades, China’s earthquake work From different perspectives, he conducted a special study on the seismological anomalies in some specific areas. Jiang Chun and Feng Deyi (1989) take the annual earthquake of magnitude 5 in North China