Abstract
On April 26 pm 3 o'clock 1974, in Akamatsu district, Okuramura, Mogamigun, Yamagata Prefecture, occured the large scale landslide (90-160m wide, 415m long) with large amount of debrisslide. The main part of village was buried under this debrisslide and then there occured heavy damage of 17 casulties and 20 razed houses.
In this area, lignite bearing sequence, which is constructed with soft lithic characters in general and contains large amount of water, is developed. In 1974, heavy snowfall (once a 20 years) attacked the proper area, and during several days before April 26 when the landslide occured, high temperature continued and caused the melting of the snowsis equivarent to the rainfall of 40mm/D.
This landslide is not caused by the breaking of the old pits, but by the superfluous humidities of upper horizone of the lignite beds. It is, so to speak, the surface landslide.
