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| | Abstract | | The fresh water lens that is on seawater is a water source on Tarama island in Okinawa Prefecture. To examine the plan for the water supply and the influence of global warming on such an island, we should understand the distribution of the fresh water lens. Then, we investigated the resistivity structure of Tarama island by TDEM expecting the boundary of the density of salinity of the groundwater and groundwater surface in the Ryukyu limestone to be understood as a resistivity change. As a result, the base of the first layer of the resistivity structure was almost corresponding to the groundwater surface. The second layer is thick in the center part and is thin in the edge part on the island. The thickness of the second layer was more intentionally larger than that of the fresh water lens confirmed in the observation wells, though the shape of the second layer harmonized with that of the fresh water lens. It is necessary to improve the survey system of TDEM and to compare with VES to clarify the shape and distribution of the fresh water lens accurately. |
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