Sulfur dioxide emissions related to volcanic activity at Asama volcano, Japan

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• 作者：Michiko Ohwada (1)
  Kohei Kazahaya (1)
  Toshiya Mori (2)
  Ryunosuke Kazahaya (1)
  Jun-ichi Hirabayashi (3)
  Makoto Miyashita (4)
  Shina Onizawa (5)
  Takehiko Mori (6)
  
• 关键词：SO2 emission rates ; B ; type earthquakes ; Volcanic activity ; Degassed and outgassed magma ; Convective degassing and outgassing of magma ; Asama volcano
• 刊名：Bulletin of Volcanology
• 出版年：2013
• 出版时间：December 2013
• 年：2013
• 卷：75
• 期：12
• 全文大小：
• 作者单位：Michiko Ohwada (1)
  Kohei Kazahaya (1)
  Toshiya Mori (2)
  Ryunosuke Kazahaya (1)
  Jun-ichi Hirabayashi (3)
  Makoto Miyashita (4)
  Shina Onizawa (5)
  Takehiko Mori (6)
  
  1. Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), Central 7, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8567, Japan
  2. Geochemical Research Center, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
  3. Volcanic Fluid Research Center, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8551, Japan
  4. Seismological and Volcanological Department, Japan Meteorological Agency, 1-3-4 Otemachi, Chiyoda-ku, Tokyo, 100-8112, Japan
  5. Meteorological Research Institute, Japan Meteorological Agency, 1-1 Nagamine, Tsukuba, Ibaraki, 305-0052, Japan
  6. Earthquake Research Institute, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan
  
• ISSN：1432-0819

文摘

A 40-year-long record of the sulfur dioxide (SO2) emission rate of Asama volcano, Japan, is presented including high-temporal-resolution data since the 2004 eruption. The 2004 and 2008009 eruptive activities were associated with high SO2 emission, and SO2 emission rates markedly fluctuated. In contrast, stable and weak SO2 emissions have been observed for the rest of the investigated interval. The fluctuation of the SO2 emission rates is correlated with the number of shallow low-frequency B-type earthquakes, implying that increased flows of gas and/or magma induced the B-type earthquakes along the shallow conduit. The total volumes of outgassed magma during the 2004 and 2008009 eruptive activities are estimated to be 1.9108 and 1.5108m3, respectively. These volumes are about 10000 times larger than those of the erupted magma, indicating that the large volumes of the magma were outgassed without being erupted (i.e., excess degassing/outgassing). Degassing and outgassing driven by magma convection rather than by permeable gas flow in the conduit is concluded as the probable degassing/outgassing process of Asama volcano based on model examinations, and is thought to occur regardless of the outgassing intensity. Production rates of outgassed magma related to the 2004 and 2008009 eruptive periods are estimated to have been 7.4103 and 6.7103kg/s, respectively. These values are one order of magnitude higher than the average production rate of 0.92103kg/s for the inactive periods. Increased supply of fresh magma is thought to activate magma convection in the conduit and to thereby increase magma degassing/outgassing.