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

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K14811
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: The 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
• 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

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.

Free Research Field

地震学

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。