A time domain electromagnetic survey (TDEM method) was conducted to investigate the resistivity structure of the crater, fumarole, and hot spring area of the Nasudake (Chausudake) volcano. The findings of this survey are as follows: (1) Under the crater area, a thin low-resistivity layer (approximately 50 m) was found on the surface, and lens-shaped high-resistivity areas continued to a depth of 800 m below it. The lens-shaped high-resistivity areas are believed to correspond to a thermal volcanic gas region. (2) From the east-west direction survey line crossing the foot of the Nasudake, two or three horizontal resistivity layer structures, which are considered to be caused by the geological structure and surface water, were observed.

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