Skip to main content

Volume 57 Supplement 8

Special Issue: Applications and Interpretation of Modern Magnetic Surveys

Magnetization intensity mapping on Unzen Volcano, Japan, determined from high-resolution, low-altitude helicopter-borne aeromagnetic survey

Abstract

On September 18, 2002, we conducted a high-resolution, low-altitude helicopter-borne aeromagnetic survey at two flight altitudes, using spiral trajectories for the first time, over Unzen Volcano in the framework of the Unzen Scientific Drilling Project (USDP). This study obtained more detailed and new information than the previous aeromagnetic studies in Unzen volcano about the geological features, for understanding the history and eruption mechanism of the Unzen volcano. Therefore, we conducted a magnetization intensity mapping on the volcano, on the assumption that the magnetic anomalies are caused by the terrain magnetized in the same direction as the present Earth’s magnetic field and the magnetization intensity varies only laterally. This map shows good agreement with the geologic features, especially the hydrothermal alteration zone and the collapsed pyroclastic deposits. In addition, even in the area covered by lavas, the magnetization intensities show various values corresponding to each eruption event. It may be considered that the differences in magnetic properties reflect different oxygen fugacity in rocks during their cooling time period. Local magnetization lows on Heisei-Shinzan suggest that the Heisei lava produced by the 1991–1995 eruption has not yet been cooled enough.

References

  • Bhattacharyya, B. K., Magnetic anomalies due to prism-shaped bodies with arbitrary polarization, Geophysics., 29, 517–531, 1964.

    Article  Google Scholar 

  • Finn, A. C. and L. A. Morgan, High-Resolution aeromagnetic mapping of volcanic terrain, Yellowstone National Park, J. Volcanol. Geotherm. Res., 115, 207–231, 2002.

    Article  Google Scholar 

  • Finn, A. C., T. Sisson, and M. Deszcz-Pan., Aerogeophysical measurements of collapse-prone hydrothermally altered zones at Mount Rainier volcano, Nature, 409, 600–603, 2001.

    Article  Google Scholar 

  • Grauch, V. J. S., A new variable-magnetization terrain correction method for aeromagnetic data, Geophysics, 52, 94–107, 1987.

    Article  Google Scholar 

  • Honkura, Y., M. Matsushima, N. Oshiman, Y. Sasai, M. Ohno, Y. Tanaka, T. Yamamoto, K. Ikeda, and Y. Wakino, Magnetization structure of the Unzen volcano determined from blimp-borne magnetic survey data, J. Geomag. Geoelectr., 47, 231–236, 1995.

    Article  Google Scholar 

  • Hoshizumi, H., K. Uto, and K. Watanabe, Geology and eruptive history of Unzen volcano, Shimabara Peninsula, Kyushu, SW Japan, J. Volcanol. Geotherm. Res., 89, 81–94, 1999.

    Article  Google Scholar 

  • Hoshizumi, H., K. Uto, A. Matsumoto, S. Xu, and K. Oguri, Geology of Unzen volcano and core stratigraphy of the flank drillings, Unzen Workshop 2002: International workshop on Unzen Scientific Drilling Project (USDP), 4–8, 2002.

    Google Scholar 

  • Makino, M., T. Nakatsuka, R. Morijiri, Y. Okubo, S. Okuma, and Y. Honkura, Derivation of three-dimensional distribution of geomagnetic anomalies from magnetic values at various elevations, Proc. 88th SEGJ Conf., Soc. Explor. Geophys. Japan, 502–507, 1993 (in Japanese).

    Google Scholar 

  • Mogi, T., Y. Tanaka, T. Morikawa, K. Kusakabe, M. Tanahashi, T. Nakatsuka, K. Tanaka and H. Utada, Subsurface structure of Unzen- Fugen and Mayu-yama Volcano inferred from airborne electromagnetic method and magnetic survey, Bull. Volcanol. Soc. Japan, 40, 263–276, 1995 (in Japanese with English abstract).

    Google Scholar 

  • Nakatsuka, T., Reduction of magnetic anomalies to and from an arbitrary surface, Butsuri-Tanko (Geophys. Explor.), 34, 332–339, 1981.

    Google Scholar 

  • Nakatsuka, T., Aeromagnetic anomalies over the area of Unzendake volcano, J. Geomag. Geoelectr., 46, 529–540, 1994.

    Article  Google Scholar 

  • Nakatsuka, T., Minimum norm inversion of magnetic anomalies with application to aeromagnetic data in the Tanna area, Central Japan, J. Geomag. Geoelectr., 47, 295–311, 1995.

    Article  Google Scholar 

  • Nakatsuka, T., Library software for geophysical data processing and representation, Geological Survey Japan Openfile Report, no. 400, 2003.

    Google Scholar 

  • Okuma, S., Magnetization intensity mapping in and arround Izu-Oshima Volcano, Japan, J. Geomag. Geoelectr., 46, 541–556, 1994.

    Article  Google Scholar 

  • Okuma, S., Magnetic constraints on the subsurface structure of Akita-Yakeyama volcano, northeast Japan, Earth Planets Space, 50, 153–163, 1998.

    Article  Google Scholar 

  • Ota, K., Unzen volcano. Nagasaki Prefecture, 98 pp., 1984 (in Japanese).

    Google Scholar 

  • Ozima, M., T. Hashimoto, and Y. Tanaka, Magnetic properties of some volcanics from Mt. Unzen, Abstracts 92nd SGEPSS Fall Meeting, C12–04, 1992.

    Google Scholar 

  • Watanabe, K. and H. Hoshizumi, Geological map of Unzen Volcano, Geological Map of Volcanoes, no. 8, Geol. Surv. Japan, 1995.

    Google Scholar 

Download references

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Ayako Okubo.

Rights and permissions

Open Access  This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.

The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Okubo, A., Tanaka, Y., Utsugi, M. et al. Magnetization intensity mapping on Unzen Volcano, Japan, determined from high-resolution, low-altitude helicopter-borne aeromagnetic survey. Earth Planet Sp 57, 743–753 (2005). https://doi.org/10.1186/BF03351853

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1186/BF03351853

Key words