数値モデル計算によるマグマ貫入に伴う地熱系発達過程の研究

概要

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Cooling of intruded magma, development and decay of hydrothermal systems are investigated by model calculations for various combination of parameters such as hydraulic permeability of the intruded magma and its surroundings. Dependence of the pressure gradient on the hydrothermal systems is also investigated to inspect the effect of the potential flow of the groundwater along the topography. In the case that the horizontal pressure gradient is smaller than buoyancy, the hydrothermal system develops just above the intruded magma, while the greater pressure gradient as well as high permeability of surroundings carries the hydrothermal system to downstream. We applied these examinations to the newly formed Nishiyama geothermal field at the time of the 2000 Usu eruption. Numerical calculations considering the real topography in and around the Nishiyama geothermal field well reproduce the observed temporal variations of geothermal field appeared on the ground surface, assuming the in-situ hydraulic permeability of the intruded magma and the surroundings as l0－12～10－13m2 and 10－l0～10－11m2, respectively.
北海道大学大学院理学研究院自然史科学部門（地球物理学）の論文
2008-03-15