Dislocation motion on an interface with friction that is dependent on sliding velocity

It is shown that smeared-out dislocations can move at a supersonic velocity across slip or fault planes if the sliding velocity across the plane is determined by a dynamic friction stress. The friction stress is assumed to decrease as the sliding velocity increases. It also is shown that smeared-out dislocations can move at the Rayleigh wave velocity if they are edge dislocations and at the transverse wave velocity if they are screw dislocations.