| Numerous studies have been conducted on snow pack characteristics associated with snow avalanches formation， mainly in North America and Europe. In recent years， the analysis about structural weakness has developing. However， existing research on mountain snow pack in Japan is aimed at the development of water resources， with the focus on determining the amount of snow water equivalent on mountains， and doesn't pay attention to avalanche disaster. The goal of this study is to fill this gap by examining the characteristics of snow pack associated with avalanches for the purpose of prevention of avalanche disaster in the Central mountainous area， Japan. We had examined these characteristic by comparing 20 snow pit data observed at fracture line of avalanche occurred in the Central mountainous area， Japan with present study results. Results of the analysis are as follows. -Most of avalanches had related to persistent weak layers such as layers consisted by near surface facetted crystals and depth hoar developed near the ground. - Weak layers consisted by rime less new snow crystals are observed significant higher frequency than Canada and Switzerland. -It suggested that critical points of fracture depth， weak layer thickness， hand hardness difference， grain size difference， are important also in Japanese snow climate. -Both of maritime and continental climate snow pack characteristics are found in closed area (Maritime: Japan sea side of main island， Continental: Pacific side of main island). |
