Thermal properties such as thermal conductivity are necessary to understand the subsurface thermal structure. It remains difficult to obtain such thermal properties without laboratory measurement on rock core samples, while such core samples are usually difficult to obtain especially at great depths. This research seeks to derive an empirical equation between thermal properties and elastic wave velocities by analysing laboratory measurement data on volcanic rock core samples. Measurements of thermal properties and elastic wave velocity have been conducted on volcanic rock core samples collected from Aso volcanic region, Japan. And correlations between measured physical properties have been discussed. Both thermal conductivity and P-wave velocity were found to decrease with increasing porosity. And thermal conductivity presented a tendency to increase as P-wave velocity increased, while an acceptable empirical equation failed to be obtained which indicated the need for further research.
A better understanding of underground phenomena associated with temperature, such as the frictional heat of faults during earthquakes, requires the study of subsurface thermal structure. Computing the thermal structure profile requires the thermal properties of rocks underground. Since it is still challenging to measure the thermal properties of rocks remotely from the ground with high operability and low cost, the predominant method of obtaining such data is laboratory measurement using rock samples. While laboratory measurement requires a certain size of samples, which are usually difficult to be retrieved at great depth and under the sea floor. On the other hand, well logging and geophysical exploration were well established and allowed the in situ physical properties underground like elastic wave velocity and resistivity obtained remotely. Therefore, correlations between these physical properties and thermal properties are of increasing interest. Thermal properties, especially thermal conductivity, are highly dependent on porosity, saturation, and mineral composition, and so does the elastic wave velocity of rocks. Based on this similarity, there is a possibility to obtain the thermal properties of rocks through elastic wave velocity data using the relationship between them.
