Geothermal model of the Kurikoma region.

概要

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Four almost independent geothermal areas are distributed in the Kurikoma region Each of them is around Late Quaternary volcanoes; namely, the Onikobe Caldera, the Narugo volcano, the Takamatsudake volcano, and the Kurikomayama volcano. Hence, the magma reservoirs, which probably exist or existed beneath these volcanoes, are considered to be heat sources of the four geothermal areas. In the center of each geothermal area, a high temperature two phase zone (water & steam) is developed at a shallow depth. The temperature of the shallow two phase zone is controlled by the boiling point for depth of the geothermal fluid. The ground temperature decreases away from the center. The geothermal fluid beneath these high temperature areas is lighter than the surrounding lower temperature fluid and consequently at deeper levels the fluid pressure, compared at the same depth below the sea level, is lower beneath these high temperature areas than beneath their surroundings. As a result geothermal fluid flows toward the high temperature areas at depth. The flow pattern of geothermal fluid beneath each geothermal area is further controlled by the topography and the geological structure of the area. In the Kurikoma region, Neogene formations and pre-Tertiary basement rocks and distributed at a comparatively shallow depth; hence, fractures in these rocks are important as the reservoir of the geothermal fluid.
日本地熱学会の論文