“…The Miocene Mizunami Group, including lignite-bearing formation in the lowermost part covers inconsistent with the Toki granite complex in excavating the area [12]. Before the excavating, it is suggested the boundary depth of the Toki granite complex and Mizunami Group [8] and regional ground water flow system based on the 100 m deep boring logging, airborne electromagnetic survey, gravity survey, and elastic wave exploration. As results of the excavating, plane of the unconformity is about 200 m deep.…”