地震によって発生する特異な土砂移動現象についての研究

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.