Intense rainfall on 11-12 July 2012（ maximum total 572 mm; maximum 4-hour rainfall 385
mm） triggered numerous landslides and associated lahars in Aso caldera, central Kyushu, southwestern
Japan. Most of the landslides were concentrated in the eastern part of Asodani Valley,
at the northern part of Aso caldera. The landslides were divided into three types: landslides
occurring at steep caldera walls, landslides generated on the slopes of the post-caldera central
cones of Aso Volcano and landslides occurring on steep slopes of Nekodake Volcano. Most of the
landslides were shallow （about 1-2 m thick） soil slips in unconsolidated fallout tephra layers
overlying lava and welded Aso pyroclastic-flow deposits, and mobilized completely into lahars.
The lahars eroded talus slopes and/or channel side slopes and transported boulders, which damaged
houses and caused fatalities at some sites. Similar landslide and associated lahar disasters
occurred at Aso Volcano in June 1953, July 1990 and June 2001. The characteristics of landslides
and lahars provide important information for preventing or mitigating future similar disasters
in the Aso caldera region.
阿蘇カルデラにおいて2012年7月の九州北部豪雨によって発生した斜面崩壊
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