关键词: 成组孕震, 华北北部, 震兆, 张北地震

Abstract: Group features of the strong shocks in North China are studied in this pa per ba sed o n a seismogenic model for group shocks and the theory of the group events dev eloped by Li Qing zu et al. The events used include the Datong-Yang gao shock ( M_S 6. 1), the Bao to u shock ( M_S 6. 4) and the Zhang bei shock ( M_S 6. 2). Combined the g eo logical structures with the recorded historical events, the model for the seismogenesis and occurrence of the Zhangbei earthquake and some precursors before it a reanalyzed. Research show that the MS 6. 2 shock occurred in Zhangbei in January of 1998 is a very important event among the group events in North China, which is in a same group with the Da tong earthquake ( M_S 6. 1, 1989) and the Baotou earthquake ( M_S 6. 4, 1996). The main active area for this group of large shocks is along the mid-western segment of the Yinshan-Yanshan seis-mic belt in North China. The frequency of shocks and the precursors in earth resistivity show that the crust in this area changed as a whole within that time interval.

Key words: Seismogenic group, Northern part of North China, Earthquake precur-sor, Zhang bei earthquake