A controversy over the last decade is the large difference in the slip-weakening distance, Dc, between laboratory-measured and seismically estimated values. Our numerical analyses of the thermal pressurization process, based on measured transport properties of the Hanaore fault zone in Japan, reveal that the process is effective for this fault and that Dc becomes of the order of several decimeters to about 1 m when the width of the deformation zone is less than 10–20 mm. This Dc value is of exactly the same order as that determined seismically, so thermal pressurization can be a mechanism for solving the Dc paradox. The thermal pressurization process effectively reduces the heat production rate. and the temperature rise expected for this fault zone is at most about 600°C, which is not high enough a temperature to melt rocks.