On the basis of the interlayer discouple model provided in 1979,we further demonstrate the various kinds of discouple forms,which occur between the granite,layer and the basalt layer.These various disco-uple forms are caused by various tectonical movements such as depression,uplift and differential movement of upper mantle.We also.discuss the inf-luence of the discouple phenomena on the occurrence of great earthquake.We demonstrate the existence of the interlayer discouple phenomena by means of the non-symmetric spatial distribution of bigger aftershocks which occurred after the great Haicheng and the Tangshan earthquakes,Those great earthquakes belong to strike slip type,and their dip angles of faults are nearly vertical.
We use the discouple phenomena to discuss the gravity adjustment process in a source volume,which occurs immediately after a gerat earth-quake.The gravity adjustment process can be used to explain that the trends of the aftershock fault plane are more scattered,the dip slip displace-ments of aftershocks are markedly bigger than that of the mainshock,and the aftershocks with dip slipping distribution mainly in the depressed region,which can be observed in the epicentral area and nearby.