ESTIMATION OF SUBSURFACE STRUCTURE OF LANDSLIDE AREA BASED ON MICROTREMOR OBSERVATION IN THE HOJOSHIMA, NAWASHIRO AND AMEDAKI AREA, TOTTORI, JAPAN

Abstract

Investigating the subsurface structure of a landslide area is important in considering the hazards of slope disasters in that area. In this study, microtremor exploration was carried out in three areas (Hojoshima, Nawashiro and Amadaki) in Tottori prefecture that were judged to be landslide topography, and the subsurface structure was estimated. The target areas are based on the landslide topography distribution map published by the National Research Institute for Earth Science and Disaster Prevention. As a result, it was found that the characteristics of tremors in the target area differ between landslide moving mass, main scarp, and original subsurface areas. In addition, the velocity structure and thickness distribution of the landslide sedimentary layer in each area could be estimated. In the Hojoshima area, where the building was damaged by the 2016 Central Tottori Earthquake, it was found that landslide moving mass was deposited on the alluvium. In the Nawashiro area, landslides occurred in three areas, and it was found that the geology and sedimentary layer thickness differed in each area. In the Amedaki area, it was found that the soft sedimentary layer of the moving mass was thin and widely distributed. In the future, it will be necessary to evaluate landslide hazards based on this subsurface structure information.