Abstract: We have analyzed the cross-fault mobile geodetic deformation data before and after the Datong and Zhangbei earthquakes. The results indicate that each strong earthquake in group activity has similar precursory anomaly of fault movement in specific tectonic sites. The process of earthquake preparation of strong earthquakes in group activity is of unity. The phase of precursory anomaly of fault movement reflects the process of energy centralization and liberation. The trace monitoring and comparative analysis of precursory anomaly is of great significance in seismic regime prediction.

Key words: Group activity, Precursory characteristic, Cross-fault geodetic deformation, Datong earthquake, Zhangbei earthquake