Specific heat capacity and thermal diffusivity and their temperature dependencies in a rock sample from adjacent to the Taiwan Chelungpu fault

Determination of the specific heat capacity and thermal diffusivity of rock samples, together with their temperature dependencies, is crucial for estimation of frictional heating during an earthquake. We measure these properties of a rock sample taken adjacent to the Taiwan Chelungpu fault, which slipped during the 1999 Chi-Chi earthquake, by differential scanning calorimetry and by using a laser-flash apparatus. We also evaluate the temperature dependencies of these properties up to 1000 degrees C and 800 degrees C, respectively, and determine their fitting equations. The specific heat capacity of the sample peaks at around 565 degrees C, and the thermal diffusivity decreases with increasing temperature to 600 degrees C but is almost constant in the temperature range of 600 degrees C-800 degrees C. These changes at around 550 degrees C-600 degrees C probably result from the alpha-beta phase transition of quartz, of which the sample is dominantly composed. We then perform a numerical analysis, adopting these values of specific heat capacity and thermal diffusivity along with their temperature dependencies, to reestimate dynamic shear stress and earthquake energetics during the Chi-Chi earthquake. In this way, we determine the residual shear stress after the stress drop to be 9.0 MPa and the energy taken up by coseismic chemical reactions to be 10.4 MJ m(-2), corresponding to 12.1% of the given work on the fault and tending to counteract the frictional heating.