| "This paper reports the results of analysis of characteristics of landslide sites, and seismic, topographic and geological characteristics of landslides that occurred in the Imokawa Basin during the magnitude-6.8 the mid Niigata prefecture earthquake in 2004. It also describes the results of consideration of field observations during the earthquake at some landslide sites where no large mass movements were observed. Investigations revealed that the sites of landslides and slope failures were distributed mostly in areas subjected to ground motion with an intensity of more than six plus and were correlated more to the maximum vertical acceleration than to the maximum horizontal acceleration. Landslides and slope failures occurred more frequently on dip slopes and convex slopes. As a result of investigations in eleven areas where field observations were made of landslides during the earthquake, local or temporary mass movements due to ground motions were observed at landslide sites with a history of sliding, but no cumulative movements were detected such as sliding that may have started right after the earthquake. At landslide sites in two areas where sliding started before the earthquake, cumulative movements were found after the occurrence of the earthquake. Sliding was assumed to have been continuing free from the effects of ground motions. " |
