Mechanisms of faulting

The faulting picture shown by E. M. ANDERSON in his book using C. E. INGLIS' stress calculations is examined, and it appears difficult to extract energy for radiation in seismic waves from such a picture. Before and after the formation of such a crack the stress energy appears to be approximately the same. However if there are two pre-existing 'lubricated' approximately co-planar sheet regions or sheet regions weaker than their surrounding rocks with a strong solid region between them, then this solid between may be ruptured and energy radiated. This may be modified to include the growth of a simple single lubricated crack but this later process does not seem adequate for large earthquakes.