Abstract
We morphometrically studied landslide features and mobility using 1: 50, 000-scale landslide maps issued by the National Research Institute for Earth Science and Disaster Prevention (NIED) of Japan. We selected 3 study areas 19 x 22 km each-the Hachimantai area composed of Quaternary volcanic rock, the Kiyokawa area of Tertiary sedimentary rock, and the Ichinose area of crystalline schist. We found that the number of landslides and slide directions were strongly regulated by geological structures in Tertiary sedimentary rock and crystalline schist. At all 3 locations, most landslide masses were longer and narrower than their source areas. In the Kiyokawa area, however, half of the number of landslidemasses were wider than their source areas . We characterized ranges of the slope angle of source areas and the equivalent coefficient offriction H/L of landslide masses as an index of landslide mobility in each test area, where L is the horizontal distance and H is the relative landslide height . H/L proved to be proportional to the slope tangent of the source area at all locations . The large surface displacement of almost all landslides exceeded the critical strain to slide, indicating that almost all landslides collapsed and slid. Our data should prove useful in predicting and mitigating landslide disasters, and further analysis of wider areas should yield even more practical information
