The influence of water on the stress supported by experimentally faulted Westerly granite

Fault zones in wet Westerly granite deformed at temperatures of 300" and 400C require markedly lower shear stresses for sliding than when dry, even when the effective confining pressure is held constant between the wet and dry tests, provided that the strain rate is lower than lO-'s-l. The rate of strength reduction is enhanced by increasing the pore water pressure. The deformation rate is a power function of the applied stress where the stress exponent is approximately 7 for pore water pressure of l00MPa and 21 for pore water pressure of 20 MPa.