Temperature Gradient Map of the Japanese Islands.

概要

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Temperature gradients were obtained from temperature logging of drillholes for geothermal explorations. These data were compiled with the published temperature gradients for terrestrial heat flow measurements to make a temperature gradient map of the Japanese Islands. Since a temperature-depth profile obtained from a drillhole near a volcanic zone is often distorted by fluid convections, it is difficult to estimate the conductive heat transfer. This complicated nature of heat transfer requires detailed heat flow studies and sufficient coverage over a volcanic zone. The proposed map is based on direct evidences of many drillhole measurements in and around the volcanic zones ranging from several hundreds meters to 3000 meters in depth. Consequently, the map can represent shallow reliable geothermal structures of volcanic zones. A significant feature of the map is a clear difference between backarc (2∼10°C/100 m) and forearc sides (1∼3°C/100 m). Temperature gradient of the Japan Sea side is predicted to be 3∼4°C/100 m from a number of data sets. The spatial variation of the Curie depths are in remarkable agreement with the temperature gradient map.
日本地熱学会の論文