Earthquakes and faults

Abstract

Abstract The hypothesis that earthquakes are caused by faulting has been prominent in seismological theory for half a century, but continues to present many difficulties. Although the chief support comes from studies of large shallow earthquakes that have been accompanied by surface faulting, the evidence given by these infrequent events can be interpreted otherwise. No satisfactory explanation of deep-focus earthquakes has emerged; sudden faulting may be essentially a surface phenomenon. Nor does the hypothesis aid the understanding of such phenomena as sudden regional uplift, or slow fault creep. There is much to encourage the view that fracture of the ground is but a gross form of earthquake damage. On the other hand, the similarity between natural earthquakes and underground nuclear explosions, as radiators of seismic waves, suggests that sudden local phase transitions may provide a source mechanism for earthquakes at all depths.