K. Fujita et al., AN INVESTIGATION OF THE RESISTIVITY STRUCTURE BENEATH OKI-DOGO ISLAND, Journal of Geomagnetism and Geoelectricity, 46(12), 1994, pp. 1083-1094
Extremely Low Frequency (ELF) and Very Low Frequency (VLF) Magnetotell
uric soundings were conducted at fourteen sites on the Oki-Dogo Island
in the Japan sea. The Oki-Dogo Island which was formed during the Mio
cene volcanic activity, mainly consists of volcanic and metamorphic ro
cks. Electrical resistivity structures revealed by the magnetotelluric
(MT) method well coincide with the classifications of the surface geo
logy. The magnetotelluric investigation of the island also suggests th
at a clear resistivity contrast exists between the eastern and western
parts of the island within a few kilometers in depth. In the western
part of the island, a relatively high conductive layer of less than 20
ohm-m is detected at a depth of 200 m. This layer is interpreted as b
eing a ''water-aquifer''. In the eastern part of the island, a relativ
ely resistive layer exists from the surface to 2 km in depth and this
resistive layer is thought to relate to past volcanic activities. The
resistivity contrast is also confirmed by the results of Schlumberger
resistivity soundings.