Prediction of earthquake-induced landslides of pyroclastic fall deposits
Earthquake-induced landslides of pyroclastic fall deposits are special because they occur on gentle slopes and are highly mobile with long runout distance; even one landslide could have hundreds of fatalities when it occurs in a populated area. We have been examining such landslides induced by 6 earthquakes in Japan and one in Indonesia with field surveys, and here summarize their geological features to establish a methodology of prediction. These case histories strongly suggest that pumice deposits and a clay mineral, halloysite, are very susceptible to earthquake shaking and those susceptible beds can be identified from the view point of volcanic stratigraphy. Landslides of pyroclastic fall deposits may occur repeatedly by earthquakes in a certain area until unstable beds are removed, so we need to consider the potential of earthquake-induced landslide is high in an area with buried pumice fall deposits at least where previous earthquakes induced such type of landslides.