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2022 年度 実績報告書

海底地震計を用いた海洋マントルの含水様式の解明

研究課題

研究課題/領域番号 20J22082
研究機関東京大学
特別研究員 KIM Hye Jeong  東京大学, 理学系研究科, 特別研究員(DC1)
研究期間 (年度) 2020-04-24 – 2023-03-31
キーワード海底地震計 / 海底堆積物 / レシバー関数
研究実績の概要

On the top of the seafloor, two layers hamper the analysis of body waves recorded by ocean bottom seismometers (OBSs). They are the layer of water mass above the OBS and the seafloor sediment layer right beneath an OBS. The seafloor sediment layer is generally thin, less than a kilometer, and the P-wave and S-wave velocities are very low. A large impedance contrast between the sediment layer and the basement basaltic crust is the cause of strong P-wave and S-wave reverberations. Effects of the seafloor sediment layer are predictable if the structure of the sediment layer is known.

Through this project, a new method that characterizes the seafloor sediment layer using body wave records of earthquakes. Records of the radial, vertical, and pressure components are used to invert the multi-layered sediment structure at the seafloor. The method can resolve the P-wave impedance, P-wave travel time, and the S-wave velocity using the Markov chain Monte Carlo approach. The method has strength in taking the noise level information to retrieve the absolute value of the parameters. Synthetic tests using various models and real data applications to two stations showed the ability of the method.

Moreover, a possible influence of the sediment layer on the OBS data is investigated. The reverberations in the sediment and water layer of the ocean bottom environment cause frequency-dependent correction terms for the shallow layers (water and sediment). Also, we could identify the potential of combining the new method with the S-receiver function and surface wave analyses.

現在までの達成度 (段落)

令和4年度が最終年度であるため、記入しない。

今後の研究の推進方策

令和4年度が最終年度であるため、記入しない。

備考

Two invited talks using the project's outcome.
(1) 2023/04 Earthquake Research Center, KIGAM, Republic of Korea
(2) 2023/02 Center for DEEP-SURFACE Coupling of Earth, SEES, SNU, Republic of Korea

  • 研究成果

    (2件)

すべて 2022

すべて 学会発表 (2件) (うち国際学会 1件)

  • [学会発表] High-resolution seismic constraint on the seafloor sediments using teleseismic body waves of ocean bottom seismometers2022

    • 著者名/発表者名
      HyeJeong Kim, Hitoshi Kawakatsu, Takeshi Akuhara, Nozomu Takeuchi
    • 学会等名
      AGU Fall Meeting 2022
    • 国際学会
  • [学会発表] High-resolution seismic constraint on the seafloor sediments using the teleseismic body waves: towards deeper structure analysis using receiver functions2022

    • 著者名/発表者名
      HyeJeong Kim, Hitoshi Kawakatsu, Takeshi Akuhara, Nozomu Takeuchi
    • 学会等名
      JpGU 2022 Meeting

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公開日: 2024-12-25  

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