Takigami geothermal system, northeastern Kyushu, Japan

The Takigami geothermal reservoir is bounded by a system of faults and fractures oriented along two main directions, north to south and east to west. The Noine fault has a large vertical displacement and trends north to south, dividing the subsurface characteristics of resistivity, permeability, temperature and reservoir depth. The Takigami geothermal ¯uid has a near neutral pH and is of the Na±Cl type, with a chloride content ranging from 400 to 600 ppm. The southwestern part of the area has the highest subsurface temperature, up to 2508C. The deep ¯uid originates from the southwest, and ¯ow is mainly to the north and partly to the east along faults and fractures, decreasing in temperature with increasing lateral ¯ow. # 2000 CNR. Published by Elsevier Science Ltd. All rights reserved