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

• Okubo Ayako

  Disaster Prevention Research Institute, Kyoto University

• Tanaka Yoshikazu

  Institute for Geothermal Sciences Graduate School of Science, Kyoto University

• Utsugi Mitsuru

  Institute for Geothermal Sciences Graduate School of Science, Kyoto University

• Kitada Naoto

  Institute for Geothermal Sciences Graduate School of Science, Kyoto University

• Shimizu Hiroshi

  Institute of Seismology and Volcanology, Faculty of Sciences, Kyushu University

• Matsushima Takeshi

  Institute of Seismology and Volcanology, Faculty of Sciences, Kyushu University

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.

Journal

• Earth, Planets and Space

  Earth, Planets and Space 57 (8), 743-753, 2005

  Society of Geomagnetism and Earth, Planetary and Space Sciences, The Seismological Society of Japan, The Volcanological Society of Japan , The Geodetic Society of Japan , The Japanese Society for Planetary Sciences

Keywords

• Aeromagnetic survey
• Unzen volcano
• magnetization intensity mapping

Details

• CRID: 1390001206512880512
• NII Article ID: 10017469848
• NII Article ID: 130003956533
• NII Book ID: AA11211921
• DOI: 10.1186/bf03351853
• ISSN: 18805981
• ISSN: 13438832
• NDL BIB ID: 7465084
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I7465084
• Web Site: https://link.springer.com/content/pdf/10.1186/BF03351853.pdf
• Web Site: https://link.springer.com/article/10.1186/BF03351853/fulltext.html
• Web Site: http://link.springer.com/content/pdf/10.1186/BF03351853
• Text Lang: en
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
• Abstract License Flag: Disallowed