[H-DS07] Landslides and related phenomena

[HDS07-04] Geological and Geomorphological Causes of Deep-seated Catastrophic Landslides in the 1953 Aridagawa Disaster

*Noriyuki Arai¹ (1.Disaster Prevention Research Institute,Kyoto University)

Keywords:deep-seated catastrophic landslide, rainfall, accretionary complex

To reveal the geological and geomorphological causes of deep-seated catastrophic landslides (DCLs) by heavy rainfall in the 1953 Aridagawa disaster, the detailed geological mapping and geomorphological analysis using the 1-m DEMs were undertook in the upper reaches of the Arida River in the Kii Mountains. This area is underlain by the Cretaceous accretionary complex, consisting of sandstone dominated alternating beds of sandstone and shale and their broken formation. As a result, southward dipping low-angle faults, shear zones of broken formation with laumontite veins and the Yanase fault formed the failure surfaces and most of the DCLs were distributed along the convex breaks of slope angle, undercut slopes and the ridge lines with deep weathered rocks.