Does the elastic rebound cause earthquakes?

Answer 1

At a slip fault the plates on either side of the fault are under a force that impels them to move past each other, but restrained by friction and the interlocking of their shapes. These opposing forces distort the rocks of the plate edges near the fault, producing elastic deformation.

When the strain becomes great enough to overcome static friction or to break the interlocking sections of rock, or when any shock occurs that jars the fault and allows it to start moving, the friction between the plates will be reduced to dynamic friction (for so long as the plates keep moving). Then elastic forces in the distorted rocks will cause them to spring suddenly back to their proper shapes, producing movement of the rocks either side of the fault, parallel to the fault, of sometimes several metres.

This sideways movement releases a great deal of elastic potential energy, producing the S-waves of an earthquake.

Elastic rebound caused a problem for seismologists monitoring underground nuclear tests before the Comprehensivve Test Ban Treaty came into effect. An explosion itself produces only P-waves, which ought to have allowed seismologist to tell underground explosions apart from earthquakes. But in practice the P-waves from the explosions could jar elastically-deformed faults into movement, which produced S-waves from the elastic rebound.