Inversion of needle-probe data for sediment thermal properties of the eastern flank of the Juan de Fuca Ridge

An estimation method is introduced for measuring thermal conductivity, thermal diffusivity, and heat capacity of sediment from temperatures using a needle probe. This method is based on the continuous cylindrical heat-source model. Thermal conductivity is estimated from needle-probe temperature data using asymptotic approximation of the model. Heat capacity is then inverted from early time temperature data using a complete form of the model. Finally, thermal diffusivity is calculated from the estimated thermal conductivity and heat capacity. Numerical experiments with synthetic temperature data indicate that the estimation error of the sediment's heat capacity is similar to 12%. The error of thermal diffusivity is thought to be greater than that of heat capacity. We apply the method to needle-probe temperature data obtained during Integrated Ocean Drilling Program Expedition 301 carried out on the eastern flank of the Juan de Fuca Ridge and estimate the sediments' thermal properties. The results indicate that thermal properties of sediments are strongly dependent on lithology and porosity. Examination results of the relations of heat capacity and thermal diffusivity to thermal conductivity show that these relations depend on the amount of quartz. The empirical formulas for these relations are provided, and they differ from those which are commonly used in thermal conductivity reduction schemes.