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Space time study in slow earthquake activity and surrounding seismic structure southern off Hokkaido using broad-band ocean bottom seismograms

Research Project

Project/Area Number 20K04122
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeMulti-year Fund
Section一般
Review Section Basic Section 17040:Solid earth sciences-related
Research InstitutionTohoku University

Principal Investigator

Azuma Ryosuke  東北大学, 理学研究科, 助教 (70620540)

Co-Investigator(Kenkyū-buntansha) 高木 涼太  東北大学, 理学研究科, 助教 (10735963)
Project Period (FY) 2020-04-01 – 2023-03-31
Project Status Completed (Fiscal Year 2022)
Budget Amount *help
¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000)
Fiscal Year 2022: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2021: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
Fiscal Year 2020: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Keywords日本・千島海溝会合部のスロー地震活動 / 微動活動の時空間発展 / 沈み込んだ海山麓のバースト微小地震活動 / 巨大地震発生がスロー地震活動に及ぼす影響 / 地震活動に伴う海底下構造の時空間変化 / スロー地震発生場のプレート境界構造 / 日本-千島海溝会合部の地震活動 / 巨大地震発生と微動活発化 / 超低周波地震の活動実態 / 地震活動と海底下構造の時空間的関係性 / 日本ー千島海溝会合部の地震活動 / 微動と通常地震の時空間的活動関連性 / 北海道襟裳沖の臨時海底地震観測 / 浅部微動活動の検出 / 地震波干渉法 / 常時微動解析 / スロー地震 / 海底地震観測 / 北海道襟裳沖
Outline of Research at the Start

北海道襟裳沖は、海山が沈み込む複雑な地下構造を持ち、スロー地震の一種である超低周波地震や低周波微動の活動度が高い。しかし、既存の定常観測網が疎な領域のため、スロー地震の分布には未解明な点が多く、沈み込む海山との関係も未解明である。スロー地震活動は震源の移動を伴って時空間的に変化し、その要因にはプレート境界面上の流体が予想され、震源近傍の観測によって流体分布の時間変化が地震学的構造の時空間変化として捉えられる可能性がある。本研究では、襟裳沖での海底地震観測を通して、スロー地震とプレート境界付近の不均質構造を結びつけることで、スロー地震発生メカニズムを明らかにする。

Outline of Final Research Achievements

This study clarified the state of the slow earthquake activity off Erimo, Hokkaido, through several OBS observations since 2003. A broadband OBS discovered the presence of broadband slow earthquakes and the new activity of tectonic tremors and burst-type repeating earthquakes at the downdip rim of the subducted seamount. Tremor activities since 2003 remain in their spatial distribution but elongate the recurrent interval influenced by the decaying afterslip of the 2003 Tokachi-oki earthquake. While slow earthquakes are thought to relate to interplate fluid migration, we indicated that an appearance of fluid-move-related structural change would depend on the depth and duration of activities. Surface wave tomography based on cross-correlation analysis of ambient noise observed at S-net stations imaged high- and low-velocity regions corresponding to huge earthquakes and slow earthquakes, respectively.

Academic Significance and Societal Importance of the Research Achievements

本研究では巨大地震の発生が浅部スロー地震の活動に密接に関わることを明らかにした。さらに、そうした陸からはるか沖合の海底下における地震活動の実態把握のためには活動域直上での観測が必要不可欠であることを改めて主張した。北海道襟裳沖は2011年東北沖地震と千島海溝巨大地震の震源域の境界に位置することから、本研究の成果はスロー地震と巨大地震の関わりの解明のみならず、巨大地震発生域間のプレート相互作用の理解に向け重要な意義を持つ。千島海溝巨大地震の発生は今後30年間に非常に高い確率で切迫し、地震津波の減災の観点からもこの海域における研究の重要性は高い。観測の継続によって一層意義深い研究となり得る。

Report

(4 results)
  • 2022 Annual Research Report   Final Research Report ( PDF )
  • 2021 Research-status Report
  • 2020 Research-status Report
  • Research Products

    (16 results)

All 2023 2022 2021 2020

All Journal Article (2 results) (of which Peer Reviewed: 2 results,  Open Access: 1 results) Presentation (14 results) (of which Int'l Joint Research: 10 results,  Invited: 1 results)

  • [Journal Article] Multimode dispersion measurement of surface waves extracted by multicomponent ambient noise cross-correlation functions2022

    • Author(s)
      Takagi Ryota、Nishida Kiwamu
    • Journal Title

      Geophysical Journal International

      Volume: 231 Issue: 2 Pages: 1196-1220

    • DOI

      10.1093/gji/ggac225

    • Related Report
      2022 Annual Research Report
    • Peer Reviewed
  • [Journal Article] Ambient noise correlation analysis of S-net records: extracting surface wave signals below instrument noise levels2021

    • Author(s)
      Takagi, R., Toyokuni, G. & Chikasada, N.
    • Journal Title

      Geophysical Journal International

      Volume: 224(3) Issue: 3 Pages: 1640-1657

    • DOI

      10.1093/gji/ggaa548

    • Related Report
      2020 Research-status Report
    • Peer Reviewed / Open Access
  • [Presentation] 稠密OBS観測から検出された日本海溝-千島海溝会合部における地震学的構造の時間変化と地震活動の関係2023

    • Author(s)
      佐藤豪大、東龍介、高木涼太、日野亮太、篠原雅尚
    • Organizer
      日本地球惑星科学連合2023年大会
    • Related Report
      2022 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Spatio-temporal seismic velocity variation near the Japan-Kuril trenches junction revealed from long-term dense-OBS network observation2022

    • Author(s)
      Takehiro Sato, Ryosuke Azuma, Ryota Takagi, Ryota Hino, Masanao Shinohara
    • Organizer
      American Geophysical Union 2022 Fall Meeting
    • Related Report
      2022 Annual Research Report
    • Int'l Joint Research
  • [Presentation] 広帯域海底地震計とF-netによる北海道襟裳沖の浅部VLFE観測2022

    • Author(s)
      東龍介、高木涼太、馬場慧、日野亮太、篠原雅尚
    • Organizer
      日本地震学会2022年度秋季大会
    • Related Report
      2022 Annual Research Report
  • [Presentation] 稠密OBSアレイ観測から検出された日本海溝-千島海溝会合部における地震波速度の時間変化2022

    • Author(s)
      佐藤豪大、東龍介、高木涼太、日野亮太、篠原雅尚
    • Organizer
      日本地震学会2022年度秋季大会
    • Related Report
      2022 Annual Research Report
  • [Presentation] Shallow VLFE activity at the Japan-Kuril trench junction region revealed from a broadband OBS array and F-net observation2022

    • Author(s)
      Ryosuke Azuma, Ryota Takagi, Satoru Baba, Ryota Hino, Masanao Shinohara
    • Organizer
      International Joint Workshop on Slow-to-Fast Earthquakes 2022
    • Related Report
      2022 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Spatio-temporal seismic velocity variation near the Japan-Kuril trenches junction revealed from long-term dense-OBS network observation2022

    • Author(s)
      Takehiro Sato, Ryosuke Azuma, Ryota Takagi, Ryota Hino, Masanao Shinohara
    • Organizer
      International Joint Workshop on Slow-to-Fast Earthquakes 2022
    • Related Report
      2022 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Attempt of seismic velocity change detection by seismic interferometry using OBSs in the Japan-Kuril trenches junction2022

    • Author(s)
      Takehiro Sato, Ryosuke Azuma, Ryota Takagi, Ryota Hino, Masanao Shinohara
    • Organizer
      日本地球惑星科学連合2022年大会
    • Related Report
      2022 Annual Research Report
    • Int'l Joint Research
  • [Presentation] 広帯域海底地震計とS-netで捉えられた日本・千島海溝会合部に沈み込む海山近傍の地震活動2021

    • Author(s)
      東 龍介・川久保 晋・高橋 秀暢・太田 雄策・高木 涼太・鈴木 秀市・佐藤 真樹子・日野 亮太・田中 伸 一・篠原 雅尚
    • Organizer
      日本地震学会2021年度秋季大会
    • Related Report
      2021 Research-status Report
  • [Presentation] 海底余震観測記録の再解析による2003年十勝沖地震 (M8.0) 直後の低周波微動活動2021

    • Author(s)
      川久保 晋・東 龍介・日野 亮太・高橋 秀暢・太田 和晃・篠原 雅尚
    • Organizer
      日本地震学会2021年度秋季大会
    • Related Report
      2021 Research-status Report
  • [Presentation] Seismicity around the subducted seamount in the trench-trench junction, southern off Hokkaido, by a broadband OBS array2021

    • Author(s)
      R. Azuma, S. Kawakubo, H. Takahashi, R. Hino, Y. Ohta, R. Takagi, S. Suzuki, M. Sato, S. Tanaka and M. Shinohara
    • Organizer
      JpGU Meeting 2021
    • Related Report
      2021 Research-status Report
    • Int'l Joint Research
  • [Presentation] Ambient noise tomography in the offshore forearc region along the Japan trench using S-net data2021

    • Author(s)
      Takagi R. and K. Nishida
    • Organizer
      JpGU Meeting 2021
    • Related Report
      2021 Research-status Report
    • Int'l Joint Research / Invited
  • [Presentation] Activity of low-frequency tremors and regular earthquakes off Erimo, Hokkaido from 2006 to 2007 by a tremor investigation based on waveform information2021

    • Author(s)
      Susumu Kawakubo, Ryosuke Azuma, Ryota Hino, Hidenobu Takahashi, Kazuaki Ohta, Masanao Shinohara
    • Organizer
      JpGU Meeting 2021
    • Related Report
      2021 Research-status Report
    • Int'l Joint Research
  • [Presentation] 自己浮上式海底地震形で捉えた2006~2007年の北海道襟裳沖浅部低周波微動活動2020

    • Author(s)
      川久保晋・東龍介・日野亮太・高橋秀暢・太田和晃・篠原雅尚
    • Organizer
      JpGU-AGU Joint Meeting 2020
    • Related Report
      2020 Research-status Report
    • Int'l Joint Research
  • [Presentation] Shallow low-frequency tremor activity off Erimo, Hokkaido from 2006 to 2007 revealed from pop-up type ocean bottom seismometers2020

    • Author(s)
      Susumu Kawakubo, Ryosuke Azuma, Ryota Hino, Hidenobu Takahashi, Kazuaki Ohta, Masanao Shinohara
    • Organizer
      Slow Earthquake Workshop 2020 Virtua
    • Related Report
      2020 Research-status Report
    • Int'l Joint Research

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Published: 2020-04-28   Modified: 2024-01-30  

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