Abstract
It is important to understand the faults and basement rock structure in hot spring area. Precise gravity survey has been conducted around the Minou fault system, Fukuoka prefecture. We set 913 measurement points in Kurume, Asakura and Ukiha cities. We carried out the frequency analysis in order to remove the regional trend and noises. A three-dimensional gravimetric modeling was conducted under the assumption of two homogeneous layers condition. The survey result indicates that there are three graben structures on the north side of the Minou fault system. The maximum depth of the grabens was estimated at about 2000 m. A steep slope with north dipping exists on the southern side of graben. We compared the locations of hot springs with the basement rock structure, which is estimated from our precise gravity survey. The result of survey indicates that almost all of the hot springs are located above the steep slope portion of the basement rock, while some of them are above the deepest or gentle slope portions of the basement.
