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 for considering the hazards of slope disasters. In this study, microtremor exploration was conducted in three areas (Hojoshima, Nawashiro, and Amadaki) in Tottori Prefecture, which were judged to have landslide topography, and the subsurface structure was estimated as well. The target areas were based on a landslide topography distribution map published by the National Research Institute for Earth Science and Disaster Prevention. The results showed that the characteristics of tremors in the target area differed between the landslide moving mass, main scarp, and original subsurface areas. In addition, the velocity structure and thickness distribution of the landslide sedimentary layers in each area were estimated. In the Hojoshima area, where a building was damaged by the 2016 Central Tottori Earthquake, it was found that a 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 subsurface structure information