Estimated thermal regime at volcanic areas in Japan

Abstract:

Borehole temperature profiles and samples in volcanic areas even at shallow depths provide valuable information about the thermal regime. Recently, drilling cores sampled from Japan Meteorological Agency’s (JMA’s) borehole type volcanic monitoring stations [Group for Drilling Core Analysis, Coordinating Committee for the Prediction of Volcanic Eruption, 2011] offers an opportunity for studying the thermal regime at 42 volcanoes in Japan. Thermal conductivity, heat capacity, and density were measured on 122 samples obtained from these JMA’s boreholes. Thermal conductivity shows good correlation with density. We also investigated continuous temperature profiles from JMA’s boreholes up to about 100 m in depth. Although less precise, these data provide most of the estimates of heat flux at volcanic areas in Japan.

On the other hand, the depth of magnetic sources based on spectrum analysis of magnetic anomaly data [e.g., Spector and Grant, 1970] can be used to estimate regional thermal structures. This analysis is still controversial, however, this depth may reflect the broad average temperature and they have been used to estimate the thermal structure in various regions.

We discuss some of the limitations and possible uses for both data sources.