Abstract
The island of Miyako is roughly triangular and very flat topography. Geologically, it consists mainly of porous, unconsolidated to partly indurated, coarse-textured limestone, resting on a bed of impervious shale, the Gusukube formation. Stracturally, the island are are tilted blocks separated by normal faults. Faulting occurred toward the end of the Tertiary, shaping the island into a series of parrallel valleys and low ridges trending northwest-southeast.
Due to high permeability of the surface layer and flat topography of the island, natural water supply on Miyako exists mainly in the form of groundwater. Hydro-geologically, the island is divided into five hydrogeologic provinces. The main part of this paper discussed the hydrogeologic provinces.