Actual Situation and Characteristics of Houses Damage Caused by Block Slides in Atsuma Town During the 2018 Hokkaido Eastern Iburi Earthquake

Abstract

Block slides were responsible for ∼70% of the damage to wooden houses caused by slope failures in Atsuma Town during the 2018 Hokkaido Eastern Iburi earthquake. In this study, we analyzed the topography of the area where block slides occurred, and quantified their source and deposition areas using ArcGIS. We collected photographs of the damaged houses taken by government agencies and the media to evaluate the degree of damage. Approximately 90% of the damaged houses were “washed out or buried.”All of the victims occurred in the houses exposed to the block slides exhibited this level of damage. The average density and sliding depth of soil were estimated by analyzing stratigraphy of the scarp and by conducting soil tests. The equation of motion was used to calculate the velocity and impact pressure of the block slides. The kinetic energy of the block slide that caused the “washed out or buried” of the houses is estimated to be approximately 313 kN/s or more.