非マグマ性の火山活動に伴う消磁及び地盤変動のソースの特徴

DOI 機関リポジトリ (HANDLE) 機関リポジトリ (HANDLE) Web Site 被引用文献3件 オープンアクセス
  • 橋本 武志
    北海道大学大学院理学研究院附属地震火山研究観測センター
  • 宇津木 充
    京都大学大学院理学研究科附属地球熱学研究施設火山研究センター
  • 大倉 敬宏
    京都大学大学院理学研究科附属地球熱学研究施設火山研究センター
  • 神田 径
    東京工業大学理学院火山流体研究センター
  • 寺田 暁彦
    東京工業大学理学院火山流体研究センター
  • 三浦 哲
    東北大学大学院理学研究科地震・噴火予知研究観測センター
  • 井口 正人
    京都大学防災研究所火山活動研究センター

書誌事項

タイトル別名
  • On the Source Characteristics of Demagnetization and Ground Deformation Associated with Non-magmatic Activity
  • ヒマグマセイ ノ カザン カツドウ ニ トモナウ ショウジオヨビ ジバン ヘンドウ ノ ソース ノ トクチョウ
公開日
2019-06-30
資源種別
journal article
DOI
  • 10.18940/kazan.64.2_103
公開者
特定非営利活動法人 日本火山学会

この論文をさがす

説明

<p>We collected information on non-magmatic unrest events reported mainly of Japanese volcanoes that have been monitored for extended time periods, with the aim of conducting a statistical evaluation of these phenomena, which can sometimes lead to an eruption. We assessed the geomagnetic field changes and ground deformation, which indicate demagnetization and inflation, respectively. We then compiled the source depth, intensity, and the rate (i.e., magnetic moment rate / deformation rate), based on the single magnetic dipole model or the Mogi model, since these models are the most frequently cited in the literature. We found clear positive correlations between the source depth and its intensity and rate, exhibiting a linear trend on the log-log scatter plots. We confirmed that all the magnetic events and some of the deformation events were plotted markedly above the cutoff line related to the detection limit. We suspected that the geometry of the monitoring network and/or the simplistic point-source modeling could contribute to these positive correlations; otherwise some physical requirements such as subsurface structure might be the cause.</p><p>Although the number of unrest events collected was small, we investigated the validity of the evaluation of these unrest events from different viewpoints. Upward deviation from the linear trend on the scatter plot was found to be a potentially useful criterion, whereas the source depth had no definitive relationship with the subsequent occurrence of eruptions.</p><p>We assert that observable non-magmatic unrest events should be plotted within a diagonal area between the lower-right and upper-left domains in a scatter plot of source intensity (or rate) and depth. This is because weak sources at great depths cannot be detected, while overly strong sources close to the ground surface are physically impossible. In the intermediate zone, “unerupted” and “erupted” unrest events both occur. Based on this idea, we propose a statistical evaluation of the severity of unrest events, by measuring the deviation from the “unerupted unrests”, although this hypothesis must be tested with a sufficient number of unrest events in the future. Meanwhile, care must be taken in interpreting the data collected here, since they are based on the simplified point-source models that assume a uniform half-space, and they may not accurately recreate the physical entities.</p><p>Further studies that can relate the physical conditions and their time evolution in the subsurface to geophysical monitoring records at the ground surface will be necessary to evaluate how such unrest events are related to eruptions.</p>

収録刊行物

  • 火山

    火山 64 (2), 103-119, 2019-06-30

    特定非営利活動法人 日本火山学会

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