Abstract
Clarification of groundwater system over wide horizontal and depth ranges is indispensable to the management and maintenance of the amount and quality of groundwater resource. Electromagnetic surveys are suitable to this clarification because of their capability of detecting deep geologic structures. This study proposes a spatial modeling of resistivity by a joint inversion of MT and AMT surveys data and a 3D interpolation method Kumamoto plain covering 35 km ×32 km, which is well-known as being rich in groundwater resource, is selected as a case study. Resultant 3D resistivity model elucidates that the shallow and deep groundwater flows are similar. In addition, a hydrogeologic model of the study is constructed as the shallow groundwater system including the first and second aquifers (0 to 500 m depth range), the shallow hydrogeologic basement rocks consisting chiefly of pre-Aso volcanic rocks (500 to 1500 m depth range), the deep groundwater system containing a large aquifer composed of the Cretaceous sandstone, Mifune formation (2000 to 3500 m depth range), and the Higo metamorphic rocks forming the deep hydrogeologic basement at the bottom.
