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| | Abstract | | Ground water in Chokai volcano slowly flows inside the fresh porous lava. The ground water is upwelling around the end of the lava flow near the coast of the Sea of Japan Tens of small spring can be seen at Kamaiso sand beach, Yuza town, Yamagata Prefecture. We carried out geophysical exploration s such as induction method, magnetic survey, and ERT (Electric Resistivity Tomography) at the area surrounding springs Using the portable electromagnetic exploration instrument called GEM 2, shallow structure of the electric conductivity was estimated. In spite of careful noise reduction, the conductivity structure might be contaminated by artificial electromagnetic noise or metal facilities above the ground. Magnetic anomaly can delineate the lava rocks buried in the beach sand. We adopted the dipole dipole array and the pole pole array in ERT. The resistivity structure estimated by ERT up to the depth of about 15 m by the dipole dipole array and to the depth of about 40 m by the pole pole array. We can estimate the path of upwelling water beneath the spring. At the shallowest path of the water is thought to be controlled by the location of solid lava rocks. |
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