Time scale of gravitational deformation of mountain body and effect of earthquake

Trench study of buried depression located on the top ridge of Dainichi Pass / Kuchisakamoto landslide

Abstract

This study clarifued the time scale of gravitational deformation of mountain body by trench analysis of buried depressions on the ridge top of high relief mountain. Study sites are located in marginal mountais of the Souther Japan Alps. Deformation of deposits were observed and dating materials such as tephra and humic soil were collected.
Deformation of the mountain mass has started before the fall of AT tephra and it newly occurred on the ridge top between falls of AT and K-Ah. It implies that gravitational deformatin of mountain mass is gradual and creep type and its time scale is longer than a few ten-thousand years. The timing of the sagging of the deposits is in15C to16C and it implies the affetion of big earthquake.