Initial Pore Pressure Ratio in the Earthquake Triggered Large-scale Landslide near Aratozawa Dam in Miyagi Prefecture, Japan

The Iwate-Miyagi inland earthquake with magnitude of 7.2 on 14 June 2008 in Tohoku region of Japan resulted in more than 4,000 landslides. The deep large-scale landslide near Aratozawa Dam in Ohu Mountains of Miyagi Prefecture occurred shortly after the earthquake. In this paper, landslide geotechnical simulation with high normal stress and pore-water pressure measurement in undrained conditions is explained through laboratory experiment by means of ring shear tests. We used the newest version of undrained dynamic loading ring shear apparatus to test volcanic tuff samples from the collapsed zone and flank side of the Aratozawa landslide. The simulation results of combined triggering factors using ring shear apparatus implied that the initiation mechanism of Aratozawa landslide was influenced by initial pore pressure before being triggered by the earthquake.