Numerical Simulation of Landslide Movement and Unzen-Mayuyama Disaster in 1792, Japan

Landslides may cause huge sediment disasters. To mitigate such sediment-induced disasters, the behavior of the landslide must be predicted, in addition to the time, the location of occurrence, and the scale of the landslide. This paper proposes a two-dimensional numerical simulation for landslides. The Mayuyama landslide of 1792, which was triggered by volcanic activity, caused one of the largest disasters in the world. To reproduce sediment movement resulting from this landslide, 2-D numerical simulation and topographical analysis are discussed. The topography of Mt. Mayuyama before the failure, the topography of the slip surface, and the characteristics of the landslide material are estimated for conducting numerical simulation. Results suggest that landslide volume is about 150 million m3 or more, the landslide probably reached the sea in only a minute, and the event may have been almost finished in a couple of minutes. Landslide velocity upon reaching the sea is estimated at 100 m/sec and the thickness of landslide front is estimated at 30 m, which are enough to generate a tsunami causing a huge disaster along the seashore of Ariake bay.