Abstract
On 6 August 1993, Kagoshima City was struck by the record-high torrential rain of 90mm/hour. A number of landslides occurred along Route 10, leaving some 800 vehicles confined in an 8-kilometer distance between Iso and Hiramatsu. Also, Ryugamizu railroad station, where a train had made an emergency stop, was hit by one of debris flows and buried in earth and sand with the crashed train.
Investigations of the Ryugamizu area after the accident show that its geological formation consists of andesite, basalt, Kekura formation and welded tuff. It was also found that the collapse was triggered by Iso tuffaceous member, component of the upper Kekura formation. Most of debris flows were identified as basalt and welded tuff. In addition, it was revealed that the Hiramatsu area geologically consists of Osakibana andesite, clastic andesite and tuiTaceous sand layer. Another finding was that a large amount of collapse occured to the Osakibana andesite which is featured by its platy joints.
