Abstract
Discriminant analyses were done using 25-m grid data for slope angle, precipitation, peak ground acceleration, geology, curvature, geological structure, and slope aspect of affected areas by the 2004 heavy rainfall in July and the Mid Niigata Prefecture Earthquake in October to explain occurrence of landslides. Amount of contribution to landslides was estimated by discriminant for each parameter. The results are as follows. The slope angle is an important contribution factor, but in the case of the heavy-rainfall, the precipitation contributes to landslides more than the slope angle. Remarkable differences of the contribution were observed in mud-rich turbidites of the Nishiyama stage and the Uonuma formation between the rain-driven failures and the earthquake-driven failures. The curvature showed larger contribution to the rain-driven failures than the earthquake-driven failures. The geology and geological structure showed large contribution to large landslides by the earthquake, and the slope aspect displays regional differences.
