ABSTRACT
Many landslides in mountain area occurred during The 2004 Mid Niigata Prefecture Earthquake in Japan. In the first half of this paper, a dip slope landslide along the Shinano River, Yokowatashi landslide, is simulated by the proposed analytical method. As seen in Figure 1(a), about 4 m thickness block of the upper
Shiroiwa layer of soft silt rock has slid down more than 72 m toward the Shinano River during the earthquake. The remaining upper Shiroiwa layer is laid on the planer bedding plane which inclination is approximately 22◦. Figure 1(b) is a close photograph showing rock sampling for the laboratory tests. A thin seam layer of 5-10 mm thick was sandwiched between the upper and lower Shiroiwa layers. The material consisting of the seam is tuff, which is like a weathered sandy rock.
