Abstract: Before the Ms 6.2 earthquake on January 10, 1998, in Zhangbei, Hebei Province, a group of precursory anomalies developed from tendency anomalies to short-term and impending precursors were observed in some wells within Beijing water well network. The distribution of these anomalies and their expression characteristics and development processes during different stages are described in detail in this paper. The results show that the internal relationship between the dynamic water-level features and the accumulative processes of stress and strain during the seismogenic processes in the source region exists, and gives helpful enlightening guidance for seismologists. Therefore, this study has a certain reference value for precursory researches of earthquake prediction.

Key words: Groundwater level anomaly, Anomalous character, Precursor phenomena, Zhangbei earthquake