ローム層分布域の人工改変地における地震時流動性地すべり --GISを用いた多摩丘陵を事例としたポテンシャル評価--

Abstract

So-called “loam” composed of primary fall-out tephras and tephric soil deposits (tephric loess) is one of the factors cause earthquake-induced landslides on hills where thick loam is preserved. To evaluate potential of slope failure by this condition in the Japanese Island, the distribution of map of loam has been reported. To assess possibilities of earthquake-induced landslides in hilly areas heavily modified by human activities, man-made landforms should be modelled at the micro-landform scale considering original loam thickness. We estimated elevation changes by cutting and fill operation in the Gotentoge and Karakida areas in the Tama Hills where the Tama New Town was built using 1:3, 000 topographical maps published in 1950s and present digital elevation model (DEM) with 5 to 2 m mesh. Also, 1:10, 000 geological map of loam was used for estimation of thickness distribution of preserved loam. By this method, we tentatively mapped earthquake-induced landslides potential for these areas, artificial landform transformation hills in the depositional area of thick tephric soil deposits.