- Open Access
A resistivity cross-section of Usu volcano, Hokkaido, Japan, by audiomagnetotelluric soundings
Earth, Planets and Space volume 50, pages339–346(1998)
We collected audio-magnetotelluric (AMT) data across Usu volcano, Hokkaido, Japan, which erupted in 1977 and is still active. We had a profile of 17 sites perpendicular to the regional tectonic strike, which crossed the 1977 cryptodome, Usu-Shinzan. Tensor-decomposed data were interpreted by a two-dimensional inversion. Outside the crater rim, the resistivity structure is simple. The resistive somma lava is underlain by a conductive substratum, implying altered Tertiary or Quaternary rocks. In the crater, there are two resistive bodies bisected by a vertical conductor, which corresponds to Usu-Shinzan fault, located at the foot of the uplift. The vertical conductor was not detected in the AMT sounding in 1985. One of the possible causes of the development of the vertical conductor is a cold water supply from the surface into the vapor dominant fracture zone. One of the resistive bodies is located beneath Usu-Shinzan and implies an intrusive magma body which caused the 1977 uplift.
Ballestracci, R. and Y. Nishida, Fracturing associated with the 1977-1978 eruption of Usu volcano, north Japan, as revealed by geophysical measurements, J. Volcano. Geotherm. Res., 94, 1913–1925, 1987.
Groom, R. W. and R. C. Bailey, Decomposition of magnetotelluric impedance tensor in the presence of local three-dimensional galvanic distortion, J. Geophys. Res., 94, 1913–1925, 1989.
Katsui, Y., H. Komuro, and T. Uda, Development of faults and growth of Usu-Shinzan cryptodome in 1977-1978 at Usu volcano, North Japan, Jour. Fac. Sci., Hokkaido Univ., Ser. IV, 21, 339–362, 1985.
Matsushima, N., M. Michiwaki, N. Okazaki, R. Ichikawa, A. Takagi, Y. Nishida, and H. Y. Mori, Self-potential studies in volcanic areas (2)-Usu, Hokkaido-Komagatake and Me-akan, Jour. Fac. Sci., Hokkaido Univ., Ser. VII (Geophysics), 8, 456–477, 1990.
Nishida, Y. and E. Miyajima, Subsurface structure of Usu volcano, Japan, as revealed by detailed magnetic survey, J. Volcano. Geotherm. Res., 22, 271–285, 1984.
Nishida, Y. and H. Tomiyama, Self-potential studies in volcanic areas (1)- Usu volcano-, Jour. Fac. Sci., Hokkaido Univ., Ser. VII (Geophysics), 8, 173–190, 1987.
Nishida, Y., M. Utsugi, H. Oshima, T. Kagiyama, T. Inoue, Y. Morita, S. Shigehara, N. Matsushima, and T. Maekawa, Resistivity structure of Usu volcano as revealed by the magnetotelluric measurements, Geophysical Bulletin of Hokkaido University, 59, 151–162, 1996 (in Japanese).
Ogawa, Y. and T. Uchida, A two-dimensional magnetotelluric inversion assuming Gaussian static shift, Geophys. J. Int., 126, 69–76, 1996.
Okada, Hm., H. Watanabe, and I. Yokoyama, Seismological significance of the 1977-1978 eruptions and the magma intrusion process of Usu volcano, Hokkaido, J. Volcano. Geotherm. Res., 9, 311–334, 1981.
Oshima, H., Gravity change associated with volcanic activity-Usu volcano, M.Sc. Thesis, Hokkaido University, 1979 (in Japanese).
Soya, T., Y. Katsui, K. Niida, and K. Sakai, Geological map of Usu volcano, in Geological Map of Volcanoes 2, Geological Survey of Japan, 1981.
Watanabe, H., H. Yamashita, and T. Maekawa, Electrical study of the 1977- 1982 activity of Usu volcano, Geophysical Bulletin of Hokkaido University, 43, 31–40, 1984 (in Japanese).
Yokoyama, I., Y. Katsui, Y. Oba, and S. Ehara, Usu-zan, its volcanic geology, history of eruption, present state of activity, and prevention of disaster, Committee for Prevention of Disasters of Hokkaido, Sapporo, 1973 (in Japanese).
About this article
Cite this article
Ogawa, Y., Matsushima, N., Oshima, H. et al. A resistivity cross-section of Usu volcano, Hokkaido, Japan, by audiomagnetotelluric soundings. Earth Planet Sp 50, 339–346 (1998) doi:10.1186/BF03352120
- Apparent Resistivity
- Static Shift
- Strike Direction
- Resistivity Structure
- Resistive Body