LAUSR

The flow-like Kataragai landslide triggered by the 2018 Western Shimane Earthquake occurred in a gentle slope out of the area which suffered from the most intense ground motion. The geotechnical and hydrological conditions are considered as the primary factors for the landslide occurrence. It is confirmed through the field survey that the Kataragai landslide occurred in a refilled slope composed of medium sand with gravel, and several small ponds scattered on the refilled slope with perennial water. The existence of downslope seepage flow was validated by self-potential tests and the seepage flows at the center of the crown near the pond are more noticeable. A weak layer with low dry density and fine-particle content was confirmed through hardness tests and penetration tests. The triaxial tests indicate that the anti-liquefaction strengths of the soils in the Kataragai landslide are relatively low on the whole, while the weak layer is the lowest. The erosion of fine content in soil due to seepage flow is responsible for the formation of the weak layer. Based on the soil property and hydrologic condition, the initiation and motion mechanisms of the Kataragai landslide were discussed as well.