THE PRECURSORY CHARACTERISTICS AND SEISMOGENIC PROCESS OF THE DATONG EARTHQUAKE IN 1989

After the Helingeer 6.3 earthquake in 1976, the earthquakes with Ml≥4 occurred on the border land of Shanxi, Hebei and Inner Mongolia showed, in general, a migration from west to east, the small earthquake activity formed a gap after 1985, and formed a band after 1987, the earliest precursory anomalies emerged round about 1985 and distributed inside the gap.The mid-term anomalies marked by a set of fault displacement anomalies started in May and June of 1978, a few anomalies of groundwater level and earth resistivity appeared as well, and all these anomalies distributed outside the gap.The short-term anomalies started in March of 1987, most of which were anomalies of groundwater regime, hydrochemistry and geomagnetism, and there were anomalies of seismomitry and deformation as well.Among them, geomagnetic anomalies mainly distributed inside the gap and its boundary region, the other anomalies extended farther along Shanxi tectonic zone and Yanshan tectonic zone.In this paper, the seismogenic process of the Datong earthquake has been inferred based on the stages of seismic activity and precursory anomalies development.