2002 Fiscal Year Final Research Report Summary
Study on mechanism of landslide-induced tsunami by sedimentrological approach
| Project/Area Number |
12574016
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 海外学術 |
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| Research Field |
Natural disaster science
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| Research Institution | Tohoku University |
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Principal Investigator |
IMAMURA Fumihiko Tohoku University.,Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (40213243)
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| Co-Investigator(Kenkyū-buntansha) |
TAKAHASHI Tomoyuki Akita University., Faculty of Engineering and Resource Science, Associate Professor, 工学資源学部, 助教授 (40261599)
MINOURA Koji Tohoku University., Graduate School of Science, Professor, 大学院・理学研究科, 教授 (10133852)
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| Project Period (FY) |
2000 – 2002
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| Keywords | Landslide tsunami / historical tsunami / sand sedimentation / field study and hydraulic experiments |
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| Research Abstract |
This study aims to study the mechanism of landslide-induced tsunami by sedimentrological approach using the tsunami sedimentation. A tsunamigenic sediment layer has been discovered in fluvio-alluvial sequences on the northern coast of the Marmara Sea, northwestern Turkey. The layer is consisting of unsorted silty coarse sand including landsnails and charcoal fragments. The AMS radiometric ages of the shells have been estimated at around BC400, AD300, AD400, and AD1,000. It is proposed that a tsunami occurred in the Marmara Sea in the middle of 11th century and invaded the fluvial plains. The older fossils were derived from the underlying horizons, and we suggest that buoyancy materials such as landshells and charcoals were isolated from liquefied sediments durlng submarine sliding. Slope failing of coastal blocks triggered by fault movement generated tsunamis, which might have transported floating materials to the backshore. The simulation model for tsunamis caused by landsliding and d
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ebris flow is proposed and compared with the result from the hydraulic experiment model with an open-channel. We applied nonlinear long-wave theory integrated over a layer with non-horizontal bottom/interface as the governing equation for the numerical model. We assume hydrostatic pressure distribution, and uniform density and velocity distributions in each layer. For the case of tsunami generation by landslide, the sea water is modeled as an upper layer for wave generation and propagation, and the landslide is modeled. We used the staggered leap-frog scheme for the linear terms and the up-wind scheme for the nonlinear terms in this study. The leap-frog scheme is a central difference scheme with a truncation error of the second order. Three parameters/coefficients of the bottom friction, the horizontal viscousity and the interactive force between landslide and tsuami rushing into water are examined through comparison with the results of hydraulic experiments. We found that the Manning coefficient of 0.12 and horizontal viscousity of 0.01 are recommended for landsliding in this study. Although the interactive force is significantly important for a tsunami generation, a more detail analysis is required to determine a value of its coefficient. Less
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Research Products
(12 results)
