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

Abstract

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.

A Numerical Analysis of Landslide Movements Considering the Erosion and Deposition along the Flow Path

“…Landslide movement governing equations suggested by Miyamoto (2010) and Fathani, Legono and Karnawati (2017) is based on the momentum conservation law. The mass movement equation is shown in Eq.…”

“…Whereas i, j are the vector units on the direction x, y on Cartesian coordinate. Average density (ρm) is described in detail by Miyamoto (2010) and Fathani, Legono and Karnawati (2017).…”

“…This prediction can be used to estimate the damage potential, to design protective measures, or to identify the possibility of secondary effects such as landslide-generated wave and landslide dam that triggers flood (McDougall and Hungr, 2004;Hungr, 2007). Miyamoto (2010) suggested a 2D numerical model simulate landslide movement in Unzen-Mayuyama, Japan. This model gave the description of the landslide velocity and the affected area with finite difference numerical scheme.…”

The Search for Tsunami Evidence in the Geological and Archaeological Records, With a Focus on Japan

“…The eruption was followed by a lava dome collapse and debris flow into Ariake Bay. The landslide is estimated to have been 30 m thick at its front and containing 150 million m 3 of sediments traveling at 100 m/s (Miyamoto 2010). The landslide triggered tsunami along 77 km of coastline around the Ariake Sea, which resulted in approximately 15,000 deaths (Shiki et al 2008:167;Smithsonian 2013).…”

Reflection of typhoon morakot — the challenge of compound disaster simulation

“…Egashira et al (1992Egashira et al ( , 1997, Itoh (2000), and Miyamoto (2002Miyamoto ( , 2010 proposed the constitutive relations for water flow and the mixture of water and sediment. They successfully simulate the progress of movable bed for landslide, debris flow, and sediment transport in the river channel.…”