STUDY OF GEOTHERMAL VARIATION IN RELATION TO LARGE EARTHQUAKES(2)THE EFFECT OF TEMPERATURE GRADIENT ON FRACTURE PROPAGATION DIRECTION FOR STRIKE-SLIP FAULT

Considering a fault of elliptical-shaped crack along which exists a uniform thermal gradi-eni. The characteristics of the direction of fracture propagation of such a crack have been analysed theoretically under uniform shear loads whose direction parallels with that of the major axis of the ellipse. The results indicate that besides the fracture branches occurring in small regions near both ends of the major axis of the crack and making an angle of about 80 with the fracture plane, non-coplanar fracture branches also appear in the middle part of the major axis and at the ends of the minor axis. The extension range oi the fracture branches is related with the aspect ratio of the crack and the thermal gradient etc.On the basis of this model, the aftershock distributions of the Tangshan, Haicheng and Lon-gling earthquakes are well explained.