Evaluating Displacement Characteristics of Sharing Zones at Different Depths for a Landslide at Toromeki, Ehime Prefecture, Japan

Abstract

The purpose of this study is to investigate the trend of landslide movement and displacement characteristics of sliding surfaces at different depths for a landslide at Toromeki, Ehime prefecture, Japan. We utilized observation data of borehole inclinometers at the three boreholes and self-recorders of groundwater level, rain-gauge situated approximately 3 km from the landslide. For the borehole located at relatively high elevation, sliding surfaces were observed at depths of 1 to 4 m and 9 to 10 m. At relatively shallow sliding surface (i.e., depth of 1 to 4 m), displacement velocity increased during the spring, summer and fall months when precipitation was higher, whereas for depth of 9 to 10 m it increased only during the period when average daily precipitation exceeded 50 mm. On the other hand, for the lowest elevation borehole, there were two sliding surfaces at different depths, but none of them showed any response to rainfall. We also found that regardless of the borehole, the sliding surfaces at different depths displace in similar directions for the landslide.