Abstract
Since, in Japan, the frequently occurring landslide area has been occupied by the people from the ancient times, the countermeasures for landslide to protect the people living at the sliding area from landslide disasters as well as to check the now-occurring landslide have been taken. Great stresses have been laid on the prediction of landslide occurrence. Investigation of the primary and provoking causes for landslide occurrence has, also, been performed together with that of the provoking causes changeable artificially. Considering at what slope of the mountainous area the landslides take place and at what part of the slope the villages are built up, it is important to study the relationship between the primary causes and the provoking ones changeable artificially. In this paper, we shall describe the relationship between the primary causes and the provoking ones, taking the case of the frequently occurring sliding area consisting of the tertiary layers along the downstream of the Sai River in the north of Nagano Prefecture.
