2022 Fiscal Year Final Research Report
Investigation on spatial-temporal variation mechanism of earthquake ground motion amplification using high-sampling borehole data
| Project/Area Number |
20K05039
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 25030:Disaster prevention engineering-related
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| Research Institution | Railway Technical Research Institute |
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Principal Investigator |
Tsuno Seiji 公益財団法人鉄道総合技術研究所, 鉄道地震工学研究センター, 主任研究員 (50644738)
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| Co-Investigator(Kenkyū-buntansha) |
山中 浩明 東京工業大学, 環境・社会理工学院, 教授 (00212291)
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Keywords | 高サンプリング / 重錘落下 / 地震 / 地震波速度 / 地震動増幅 / スペクトル比 / 不整形地盤 / 凍結 |
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| Outline of Final Research Achievements |
We recognized a clear difference between P-wave velocities from the high-sampling weight drop and seismic data at the temporary earthquake observation station, Kumamoto. Therefore, we investigated the relationships between earthquake ground motion amplifications depending on epicentral azimuth and irregularities of subsurface structure. As a result, it was clarified that the surface/borehole spectral ratios of earthquake ground motions differ when those with different epicentral azimuths are incident on the irregular subsurface structure. Also, we calculated ground/surface spectral ratios for the normal and frozen seasons in Kitami City and showed that the ground/surface spectral ratios during the normal season increased at more than 20 Hz compared to that during the frozen season. We concluded that the S-wave velocity contrast between the surface and basement layers was reduced by freezing, or the S-wave velocity between the surface layer and the basement was reversed.
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| Free Research Field |
地震工学、強震動地震学、地盤震動特性
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| Academic Significance and Societal Importance of the Research Achievements |
地震動や物理探査に対する高サンプリングの実測データを通じて、表層地盤の不整形性のみならず、その方向依存性が地震動評価に重要であることを示した本研究成果は、現状の地震動予測のばらつきを減少させることができることを示した。また、凍結地盤に対する研究成果では、凍結により表層と基盤のS波速度コントラストが小さくなるあるいは表層と基盤のS波速度が逆転することを明らかにし、凍結期と通常期に区別して地震動増幅を評価することが重要であることを示した。
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