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

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• 作者：Ayako Okubo ; Yoshikazu Tanaka ; Mitsuru Utsugi ; Naoto Kitada…
• 关键词：Aeromagnetic survey ; Unzen volcano ; magnetization intensity mapping
• 刊名：Earth, Planets and Space
• 出版年：2005
• 出版时间：August 2005
• 年：2005
• 卷：57
• 期：8
• 页码：743-753
• 全文大小：3045KB
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• 作者单位：Ayako Okubo (17)
  Yoshikazu Tanaka (27)
  Mitsuru Utsugi (27)
  Naoto Kitada (27)
  Hiroshi Shimizu (37)
  Takeshi Matsushima (37)
  
  17. Disaster Prevention Research Institute, Kyoto University, Kyoto, 611-0011, Japan
  27. Institute for Geothermal Sciences Graduate School of Science, Kyoto University, Kumamoto, 869-1404, Japan
  37. Institute of Seismology and Volcanology, Faculty of Sciences, Kyushu University, Nagasaki, 855-0843, Japan
  
• 刊物类别：Earth Sciences, general; Geology; Geophysics/Geodesy;
• 刊物主题：Earth Sciences, general; Geology; Geophysics/Geodesy;
• 出版者：Springer Berlin Heidelberg
• ISSN：1880-5981

文摘

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 1991-995 eruption has not yet been cooled enough. Key words Aeromagnetic survey Unzen volcano magnetization intensity mapping