Most of you have seen these figures by Lachenbruch and Sass where they search for frictional heat generated along the San Andreas Fault. The fact that they don�t observe any heat flow �anomaly� around the San Andreas has been one of the most cited arguments for the frictional properties of active faults.
But one of the biggest criticisms of these data is that they are SURFACE DATA. Heat is generated throughout the seismogenic zone and in the time that it takes to conduct to the surface, groundwater flow could �wash out� and disperse the heat.