THE 1983 HEZE EARTHQUAKE OF MAGNITUDE 5.9

An earthquake of magnitude 5.9, of a singleshock category occurred on November 7, 1983 in Heze county, Shandong province. Some interesting seismic features about the earthquake are found: no foreshoeks, very few aftershocks with strong attenuation of seismic energy; the epicenters of aftershocks clustered and the early aftershocks oeurred in pairs or groups; the isoseismal lines of intensity are distorted and the inner isoseis-mals are butterfly-shaped with two axes striking NE and WNW respectively, etc. In the present study, the nature and the fracture model of the main shock are discussed preliminarily.