| Project/Area Number |
20J22082
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| Research Category |
Grant-in-Aid for JSPS Fellows
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| Allocation Type | Single-year Grants |
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| Section | 国内 |
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| Review Section |
Basic Section 17040:Solid earth sciences-related
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KIM Hye Jeong (2020-2021) 東京大学, 理学系研究科, 特別研究員(DC1)
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| Research Fellow |
KIM Hye Jeong (2022) 東京大学, 理学系研究科, 特別研究員(DC1)
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| Project Period (FY) |
2020-04-24 – 2023-03-31
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| Project Status |
Completed (Fiscal Year 2022)
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| Budget Amount *help |
¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 2022: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2021: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2020: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | 海底地震計 / 海底堆積物 / レシバー関数 / 沈み込み帯 / レシーバー関数 / 海底地震観測 / 堆積層 / 地震波速度構造 / スラブ / レシーバー関数 |
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| Outline of Research at the Start |
Utilizing the in situ observation of the oceanic plates is key to estimate the water content of the oceanic lithosphere. Numerous broadband ocean bottom seismometer experiments have been conducted by Japan and other institutions worldwide, which allows analyzing regions of various circumstances. I propose to develop an analysis method that can utilize both event and ambient noise signal waveforms to constrain the water existence. It will help to overcome the previous difficulties of analysis and construct a comprehensive understanding of the hydration process of the oceanic plates.
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| Outline of Annual Research Achievements |
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.
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| Research Progress Status |
令和4年度が最終年度であるため、記入しない。
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| Strategy for Future Research Activity |
令和4年度が最終年度であるため、記入しない。
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