A wide-area risk re-evaluation for seismic slope failures in 2008 Iwate-Miyagi Nairiku Earthquake

Abstract

Recently, many earthquakes have occurred frequently in various countries in the world including Japan. In cases where the epicenter is located in mountainous area, a number of seismic slope failures tend to happen. But it is very difficult to analyze detailed mechanisms of each failure due to its wide range of impact. Simple and preliminary assessment of slope failure risk based on geological and geomorphological viewpoint will provide us with useful knowledge for future hazard quantification and countermeasures. It has been expected to develop a numerical system based on simple tools with use of only digital elevation model data and conventional regional geological information. In this study, a case study is demonstrated with use of a wide-area simple seismic slope failure risk evaluation system based on 3D dynamic FEM named as BESSRA, developed by the authors before. In the analysis, the soils in each layer follow the elasto-plastic model with considering cyclic loading effects. The proposed system has inexpensive specifications that do not require an environment such as high-performance parallel computers, owing that the concept of substructures in which computational processing is completed independently at each computational node are utilized. The effectiveness of the proposed system is verified through the simulation of observed slope failure distributions in the 2008 Iwate-Miyagi Nairiku Earthquake in Japan. Finally, a detailed discussion for improvement of the numerical modeling in the proposed system is presented.