Brian, yes, water lowers melting point. I forgot about that when I made my post. But, the fluid pressure in water or any fluid also holds the fault apart (reduces the effective stress perpendicular to the fault surface)so that it does not take as much differential (deviatopric? I get them mixed up) stress to make an earthquake. Stress drop is involved in the energy of an earthquake (I think). The fluids may tend also to diffuse heat generated.
Chris