- Open Access
Electrical conductivity structures estimated by thin sheet inversion, with special attention to the Beppu-Shimabara graben in central Kyushu, Japan
Earth, Planets and Space volume 57, pages605–612(2005)
It is proposed that the Beppu-Shimabara graben (BSG), characterized by the continuous negative Bouguer anomaly, runs NE to SW in central Kyushu. In order to clarify the BSG, the shallow electrical conductivity structure in central Kyushu is obtained by thin sheet modeling using the inversion of a conjugate gradient relaxation method and also using the forward method. The data used are the single-site transfer functions at 75 sites for the periods of 77, 97 and 122 sec. The inverted model indicates three highly conductive areas: these are the Saga-Chikugo plain covered with thick alluvium and the eastern and the western parts of central Kyushu including the BSG. Both end zones of this BSG are highly conductive in our model, which is closely related to conductive layers shallower than about 1 km. In contrast, the central part of the BSG is rather highly resistive. The BSG, thus, is not revealed as a continuous high-conductive belt and seems to be separated into three parts; the eastern and the western high-conductive zones and the central resistive area in our geoelectrical model of the shallow crust.
Agarwal, A. K. and J. T. Weaver, Regional electromagnetic induction around the Indian peninsula and Sri Lanka; a three dimensional numerical study using the thin sheet approximation, Phys. Earth Planet. Inter., 54, 320–331, 1989.
Editorial Committee of Kyushu, Part 9 of Regional Geology of Japan, Regional Geology of Japan Part 9 Kyushu, 371 pp., Kyoritsu Shuppan, Tokyo, 1992.
Egbert, E. D. and J. R. Booker, Robust estimation of geomagnetic transfer functions, Geophy. J. R. Astr. Soc., 87, 173–194, 1986.
Eguchi, T. and S. Uyeda, Seismotectonics of the Okinawa Trough and Ryukyu Arc, Mem. Geol. Soc. China, 5, 189–210, 1983.
Geological Survey of Japan, Gravity map of Fukuoka district (Bouguer anomaly), Geol. Surv. Japan, 2002a.
Geological Survey of Japan, Gravity map of Ooita district (Bouguer anomaly), Geol. Surv. Japan, 2002b.
Handa, S., Y. Tanaka, and A. Suzuki, The electrical high conductivity layer beneath the northern Okinawa Trough, inferred from geomagnetic depth sounding in Northern and Central Kyushu, Japan, J. Geomag. Geoelectr., 44, 505–520, 1992.
Kamata, H., Volcanic and structural history of the Hohi volcanic zone, central Kyushu, Japan, Bull. Volcanol., 51, 315–332, 1989.
Kamata, H., Subsurface geologic structure and its genesis of Beppu Bay and adjacent area in central Kyushu, Japan, J. Geol. Soc. Japan, 99, 39–46, 1993 (in Japanese with English abstract).
Kuvshinov, A. V., D. B. Avdeev, and O. V. Pankratov, Global induction by Sq and Dst sources in the presence of oceans: bimodal solutions for nonuniform spherical surface shells above radially symmetric earth models in comparison to observations, Geophys. J. Int., 137, 630–650, 1999.
Matsumoto, Y., Some problems on the volcanic activities and depression structures in Kyushu, Japan, Mem. Geol. Soc. Japan, 16, 127–139, 1979 (in Japanese).
McKirdy, D. McA., J. T. Weaver, and T. W. Dawson, Induction in a thin sheet of variable conductance at the surface of a stratified earth—II. Three-dimensional theory, Geophy. J. R. Astr. Soc., 80, 177–194, 1985.
Nakada, T. and H. Kamata, Temporal change in chemistry of magma source under Central Kyushu, Southwest Japan: progressive contamination of mantle wedge, Bull. Volcanol., 53, 195–206, 1991.
NEDO, Report of the resistively survey (MT and CSAMT) in the Tsurumi-Dake area, NEDO, 1989 (in Japanese).
Nishida, Y., Conductivity anomalies in the southern half of Hokkaido, Japan, J. Geomag. Geoelectr., 28, 375–394, 1976.
Parkinson, W. D., The influence of continents and oceans on geomagnetic variation, Geophys. J., 6, 441–449, 1962.
Schmucker, U., Anomalies of geomagnetic variations in the southwestern United States, Bull. Scripps Inst., 13, Univ. of Calif. Press, 1970.
Shimoizumi, M., T. Mogi, M. Nakada, T. Yukutake, S. Handa, Y. Tanaka, and H. Utada, Electrical conductivity anomalies beneath the western sea of Kyushu, Japan, Geophys. Res. Lett., 24, 1551–1554, 1997.
Wang, L. J. and F. E. M. Lilley, Inversion of magnetometer array data by thin-sheet modelling, Geophys. J. Int., 137, 128–138, 1
Yamamoto, T., T. Kagiyama, and H. Utada, Resistivity structure by ULF-MT around Unzen Volcano, SW Japan, 13th Workshop on Electromagn. Ind. In the Earth, 1996.
Yusa, Y., K. Takemura, K. Kitaoka, K. Kamiyama, S. Horie, I. Nakagawa, Y. Kobayashi, A. Kubotera, Y. Sudo, T Ikawa, and M. Asada, Subsurface structure of Beppu Bay (Kyushu, Japan) by seismic reflection and gravity survey, Zisin, 45, 199–212, 1992 (in Japanese with English abstract).
About this article
Cite this article
Handa, S. Electrical conductivity structures estimated by thin sheet inversion, with special attention to the Beppu-Shimabara graben in central Kyushu, Japan. Earth Planet Sp 57, 605–612 (2005). https://doi.org/10.1186/BF03351839
- Electrical conductivity
- Beppu-Shimabara graben
- thin sheet model