Magnetic minerals, such as iron, are contained in natural materials like rocks or sediments. These minerals possess the property of acquiring magnetization that corresponds to the prevalent geomagnetism at the time of their formation.

  After acquisition, the magnetization is preserved for a few million years as remanent magnetization, which can provide us with an index related to the direction and inclination of the magnetic north. We can thus discuss whether the materials at a certain place were displaced due to a landslide or a bedrock collapse in the past.

  In this study, we measured remanent magnetization and mineral composition and age of the Quaternary volcanic products around the Gassan Shizu landslide area for the purpose of elucidating the landslide process of movement and spectrum.

  The analysis results have become indexes of risk assessment and countermeasure-planning of the Gassan-Shizu landslide.

  This paper presents a method to evaluate the urgency of failure based on temporal variation in strain and strain rate observed in the 34 landslides. The results show that the reliability of conventional prediction method of failure time tended to be improved by use of data observed after the rapid increase of strain and strain rate (acceleration point). In collected records, the strain and strain rate at the acceleration point and just before failure exceeded certain values. These results suggest that the urgency of failure can be classified into three stages by setting threshold values for strain and strain rate of landslide.