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Investigation of megathrust seismogenic zone by high-frequency receiver functions with dense array of ocean-bottom seismometers

Research Project

Project/Area Number 19K14811
Research Category

Grant-in-Aid for Early-Career Scientists

Allocation TypeMulti-year Fund
Review Section Basic Section 17040:Solid earth sciences-related
Research InstitutionThe University of Tokyo

Principal Investigator

Akuhara Takeshi  東京大学, 地震研究所, 助教 (30802954)

Project Period (FY) 2019-04-01 – 2022-03-31
Project Status Completed (Fiscal Year 2021)
Budget Amount *help
¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000)
Fiscal Year 2021: ¥390,000 (Direct Cost: ¥300,000、Indirect Cost: ¥90,000)
Fiscal Year 2020: ¥390,000 (Direct Cost: ¥300,000、Indirect Cost: ¥90,000)
Fiscal Year 2019: ¥3,510,000 (Direct Cost: ¥2,700,000、Indirect Cost: ¥810,000)
Keywords沈み込み帯 / 巨大地震断層 / 海底地震計 / 波形解析 / ベイズ統計 / レシーバ関数 / 表面波 / 地震波解析 / 海域地震観測 / 地震波形解析 / 地震波速度構造
Outline of Research at the Start

沈み込み帯で発生する巨大地震のふるまいを理解するためには、地震が起こる場所、すなわちプレート境界面の調査が必要となります。本研究では、海底地震計で観測された地震波形データを解析することで、プレート境界面の調査を行います。「①密な観測点を設置すること」、および「②新しく開発したデータ解析手法を用いること」で、従来の研究よりも高い解像度で、プレート境界面の実態に迫ることを目指します。

Outline of Final Research Achievements

In order to understand the slip behavior of megathrusts in subduction zones, it is essential to understand the physical properties of the fault plane, especially pore fluid pressure. In this study, we aim to investigate fluid pressure through waveform analysis of natural earthquakes with densely installed ocean-bottom seismometers (OBSs).
Waveforms of natural earthquakes generally show complex waveforms.In addition, multiple reflected waves trapped in seawater or in soft marine sediments further promote this complexity. Therefore, OBS records have been considered unsuitable for detailed subsurface structural analysis. In this study, this challenge is overcome by modern analytical methods using Bayesian statistics.

Academic Significance and Societal Importance of the Research Achievements

本研究では、海底地震計で記録された自然地震データを利用した解析により、沈み込み帯巨大地震断層面近傍の構造を推定できることが新たに明らかとなった。この自然地震を用いた手法では、従来の人工震源を用いた探査とは異なる物理量に感度があるため、断層面近傍の物性をよりよく拘束することができる。今後、同様な稠密観測を進め、巨大地震断層面の物性をマッピングすることで、巨大地震の被害予測向上につながると期待される。

Report

(4 results)
  • 2021 Annual Research Report   Final Research Report ( PDF )
  • 2020 Research-status Report
  • 2019 Research-status Report
  • Research Products

    (11 results)

All 2022 2021 2020 2019 Other

All Journal Article (1 results) (of which Peer Reviewed: 1 results,  Open Access: 1 results) Presentation (8 results) (of which Int'l Joint Research: 5 results,  Invited: 1 results) Remarks (2 results)

  • [Journal Article] Overpressured Underthrust Sediment in the Nankai Trough Forearc Inferred From Transdimensional Inversion of High‐Frequency Teleseismic Waveforms2020

    • Author(s)
      Akuhara Takeshi、Tsuji Takeshi、Tonegawa Takashi
    • Journal Title

      Geophysical Research Letters

      Volume: 47 Issue: 15

    • DOI

      10.1029/2020gl088280

    • Related Report
      2020 Research-status Report
    • Peer Reviewed / Open Access
  • [Presentation] Fluid reservoir in the Hyuganada accretionary prism related to the ridge subduction: implication from a passive seismic array2022

    • Author(s)
      Takeshi Akuhara, Yusuke Yamashita, Shukei Ohyanagi, Yasunori Sawaki, Tomoaki Yamada, Masanao Shinohara
    • Organizer
      Japan Geoscience Union Meeting 2022
    • Related Report
      2021 Annual Research Report
    • Invited
  • [Presentation] Passive seismic observation at Kumano-nada toward high-resolution study of slow earthquakes2021

    • Author(s)
      Takeshi Akuhara, Hiroko Sugioka, Yusuke Yamashita, Shukei Ohyanagi, Atikul Haque Farazi, Yoshihiro Ito, Ryota Hino, Ryosuke Azuma, Eiichiro Araki, Takashi Tonegawa, Takeshi Tsuji, Kimihiro Mochizuki, Tomoaki Yamada, Shunsuke Takemura, Masanao Shinohara
    • Organizer
      International Joint Workshop on Slow Earthquakes 2021
    • Related Report
      2021 Annual Research Report
    • Int'l Joint Research
  • [Presentation] 海域機動地震観測による熊野灘のスロー地震調査2021

    • Author(s)
      悪原岳,杉岡裕子,山下裕亮・大柳修慧・Atikul Haque Farazi・伊藤喜宏,日野亮太・東龍介,荒木英一郎・利根川貴志,辻健,望月公廣・山田知朗・武村俊介・篠原雅尚
    • Organizer
      海と地球のシンポジウム2021
    • Related Report
      2021 Annual Research Report
  • [Presentation] Overpressured underthrust sediment in the Nankai Trough forearc revealed by high-frequency receiver function inversion2020

    • Author(s)
      Takeshi Akuhara, Takeshi Tsuji, Takashi Tonegawa
    • Organizer
      JpGU-AGU Joint Meeting 2020
    • Related Report
      2020 Research-status Report
    • Int'l Joint Research
  • [Presentation] Development of seismic inversion tool for flat and isotropic layered structures in the ocean (SEIS-FILO)2020

    • Author(s)
      Takeshi Akuhara
    • Organizer
      JpGU-AGU Joint Meeting 2020
    • Related Report
      2020 Research-status Report
    • Int'l Joint Research
  • [Presentation] Seismic transdimensional inversion tools for flat and isotropic layered structures in the ocean (SEIS-FILO)2020

    • Author(s)
      Takeshi Akuhara
    • Organizer
      American Geophysical Union Fall Meeting 2020
    • Related Report
      2020 Research-status Report
    • Int'l Joint Research
  • [Presentation] Constraining S Wave Velocity of the Source Region of Shallow Very Low-Frequency Earthquakes2019

    • Author(s)
      Takeshi Akuhara, Takashi Tonegawa
    • Organizer
      日本地球惑星科学連合2019年大会
    • Related Report
      2019 Research-status Report
  • [Presentation] Sediment compaction and fluid processes in the Nankai Trough forearc inferred from teleseismic body waves2019

    • Author(s)
      Takeshi Akuhara, Takeshi Tsuji, Takashi Tonegawa
    • Organizer
      American Geophysical Union Fall Meeting 2019
    • Related Report
      2019 Research-status Report
    • Int'l Joint Research
  • [Remarks] SEIS_FILO(地震波データ解析用プログラムパッケージ)

    • URL

      https://github.com/akuhara/SEIS_FILO

    • Related Report
      2021 Annual Research Report 2020 Research-status Report
  • [Remarks] 自然地震波の解析で明らかとなった沈み込む堆積層内の高間隙流体圧

    • URL

      https://www.eri.u-tokyo.ac.jp/research/11785/

    • Related Report
      2020 Research-status Report

URL: 

Published: 2019-04-18   Modified: 2023-01-30  

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