A model for tsunamis caused by a sequential process from landsliding to debris flow is proposed and applied to the cases of the 1741 Oshima-oshima volcanic tsunami in Japan and the 1998 Aitape tsunami in Papua New Guinea. In both cases the observed tsunami heights were locally very large. A numerical model combining a circular-arc slip for sliding with two-layer flow model for debris flow is developed to simulate tstmamis due to land/underwater sliding. Stability conditions for CFL, open boundary, and splash of debris flow into seawater are discussed. One stability condition of the numerical model is that ∆x/∆t = max(C1, C2) should be less than unity. A stable numerical model of the splash of debris flow is obtained by introducing a drag force at the front and artificial viscosity. The model could well reproduce the distribution of tsunami heights along the coast in the southwestern part of Hokkaido, Japan. The numerical result for the 1998 Papua-New Guinea tsunami suggests a sediment slump 10–20 km offshore the lagoon as an additional source important for recreating the reported tsunami behavior.
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- Modeling for Tsunamis Generated by Landsliding and Debris Flow
Specialist MD. Monzur Alam Imteaz
- Springer Netherlands