Interactions between Temperature and Pore-Fluid Pressure during Earthquake Faulting and a Mechanism for Partial or Total Stress Relief

At depths in the crust greater than perhaps 1 km, local melting with production of pseudotachylyte should take place on fault planes during seismic faulting1,2. But, although many ancient fault zones are now exposed at erosion levels which correspond to depths of several kilometres when the faults were active, very few of them contain pseudotachylyte; it has been suggested3,4 that the general absence of this material on fault planes puts an upper limit on the magnitude of shear stresses associated with earthquake faulting. In refs 1–4 earthquake fault models with heat generated by dry frictional sliding on a single plane across which there is a constant normal stress are used. Two other factors are probably dominant in controlling the temperature rise on a fault, and the second has important implications with regard to the seismic source mechanism, and the nature of cataclastic rocks produced by rapid faulting.