| In order to gain more insight into the properties of non persistent weak layers consisted of precipitation particles， fourteen measurement data sets were analyzed. All of data sets were collected from avalanche fracture lines or flat sites near avalanche starting zones when notable avalanche activities related to such weak layers were observed in Japan. Large size (diameter 1.5 to 3.0 mm) stellar or dendrite planar crystals are found all of cases. Weak layers were found various depths (11 to 117cm) and had 1 to 5 cm thickness. The range of density of observed layers was 63 to 250 kgm-3. The relationship between density and shear frame index was similar to persistent weak layers rather than non persistent weak layers reported by Jamieson and Johnston (2001). And it was very weaker than reported by Yamanoi and Endo (2002) and Perla et al. (1982) with same density. Additional studies involving the analysis of larger data sets collected from various snow climate regions are necessary. However our results suggest importance of identification of types of precipitation particles in current snowpack for the researches concerned with snow stability evaluation and avalanche forecast related to non persistent weak layers. |
