Thermal properties across the Chelungpu fault zone and evaluations of positive thermal anomaly on the slip zones: Are these residuals of heat from faulting?

Abstract

Thermal properties of the fault zone materials are of fundamental importance for estimate of frictional heat generation during earthquake. The properties across the Chelungpu fault zone activated by 1999 Chi‐Chi earthquake, Taiwan, are measured using the drilled core penetrating the fault zone at around 1100 m depth. The fault zone contains four distinct fracture zones, each of which includes thin slip zones. Thermal conductivity (K) lies between 1.0 and 3.0 Wm−1K−1 and shows the lowest value at the slip zones. Thermal diffusivity (α) varies between 0.8 to 2.0 × 10−6 m2s−1, and is relatively low at the slip zones. Density (ρ) varies between 2200 to 2800 kgm−3 and shows the lowest values at a particular slip zone (1110 m depth). Specific heat (c) is calculated by using above data resulting in the values from 300 to 1000 Jkg−1K−1, and lowest values for slip zones. Using these data and spectral gamma ray logs, reported positive thermal anomalies at the slip zones are re‐examined whether they are regarded as residual heat from friction by faulting.