The Kumamoto earthquake of 2016 triggered numerous landslides. One feature of these landslides was fluidic movement of soil mass, which occurred despite little rain having fallen for a long time before the earthquake. To understand this distinctive phenomenon, we analyzed the seismic and soil characteristics of the area and evaluated their association with landslides. The results showed landslides to be concentrated in areas where seismic acceleration exceeded 800 gal. Through soil tests, we found that a mass of clay with abundant Halloysite easily becomes fluid. Therefore we inferred that some landslides were induced by fluidization of such clay layers.

本研究の一部は、国土交通省河川砂防技術開発公募の砂防技術分野（平成29～31年度）「大規模地震とそれに伴う地盤の劣化に起因する連鎖複合型土砂災害の発生機構と対策」（研究代表者：丸谷知己北海道大学大学院特任教授）から支援を受けて行うことができました。