THE CHARACTERISTICS OF SMALL EARTHQUAKES ACTIVITY OF THE ZHANGBEI M6.2EARTHQUAKE

By analysis and study of M₁≥1.0 earthquakes activities in the northwest area of Beijing in 1993-1998,it has been obtained that the Zhangbei M6.2 earthquake occurred on the composite position of the east-west striking Quarternary fault and Wanquan fault.The seismic activities were frequant on Wanguan fault and Zijingguan fault in recent years before the earthquake,and there was an obvious seismic migrating activity from north to south on the Wanquan fault.There is abundant precursory information of VP/VS ratio,seismogenic gap and seismic migration after1993 for analysis.