Abstract
The fault-slip motion of an earthquake is described on the basis of the recognition that frictional characteristics of the fault surfaces are important factors to be considered insofar as an earthquake source is a shear-type dislocation accompanying fracture or stick-slip. Expressions for the fault-slip velocity and acceleration are derived in terms of the stress drop (or the stress defined by the difference between the critical stress necessary to initiate slippage or fracture and the kinetic frictional stress in solid friction), the rigidity, the shear wave velocity, a parameter p standing for the magnitude of viscous friction on the fault plane and another parameter c, whose magnitude may depend upon the surface conditions such as roughness, of a natural fault and upon the bounded nature of the fault. It is shown that whether the stress after the earthquake dislocation is larger than the average kinetic frictional stress or not depends upon p and c.
