Size-distance relationships for hummocks on volcanic rockslide-debris avalanche deposits in Japan

► Relation of hummock size with its runout distance of debris avalanches is examined. ► Hummock size decrease is expressed as an exponential function of distance. ► Intercept coefficient of the function shows a correlation with collapse volume. ► Slope coefficient of the function correlates with the mobility of the avalanche. ► Hummock analysis will reveal the volume and mobility of the unknown events as well.