Abstract
collapse accident of a snow patch occurred at Mt. Arasawa, Niigata Prefecture, on August 1,2004. This accident claimed the lives of 3 amateur photographers who were taking photographs within a large snow tunnel formed by the snow melting underneath the snow patch. Since such accidents have not been studied thus far, we carried out firsthand observations at the accident site on Mt. Arasawa on August 3,2004. In addition, data and information related to collapse accidents of snow patches in Japan were collected from national and local newspaper articles. We then carried out a statistical analysis of data for the past 40 years from 1995 to 2004 to reveal the characteristics of this type of accident. A survey of the snow patch on Mt. Arasawa indicated that the collapsed snow area was as large as 220m2 , and the mass of the collapsed snow was estimated to be 150-230 ton. Since the roof of the snow tunnel may have become a cantilever structure immediately before the accident, this type of large-scale collapse was presumed to be caused by tensile fracture at the fixed end of the roof because of its weight. From the casualty analysis, data for 45 accidents and 62 casualties of snow patch collapses were compiled for the past 40 years. It was clarified that there were many accidents and casualties in the Gunma Prefecture (Mt. Tanigawa) and Toyama Prefecture (Northern Japanese Alps). As compared to accidents over the last 40 years, the accident at Mt. Arasawa in 2004 is characterized by the largest number of fatalities.
