Creep Movement and Steep-Slope Failure in Kanto Region

Abstract

The writers plotted a location of active mass movennent on a 30“×45” mesh map.It depends on an observation of a stereoscopic pair of aerophotos and surficial survey. Mass movement lies on the elevated side of thrust fault, an anticlinal axis of active folding and the margin of a tectonic basin. Such statistics are shown in this paper.
Itoigawa-Shizuoka tectonic line is a greatest thrust fault which has been identified with a boundary line between Eurasian and North American plates since the Central Japan Sea earthquake 1983.
The division of creep movement and landfall depends on the facies of layer. Clayey soil introduces creep movement and sandy one an accidental fall by heavy stormy rain or the earthquake. Ancient or fossil mass movement marks are found independent of present crustal movement. Artificial land development may lead slope disasters. They may issue from fossil landslides.
Deposits of dam sites-Miwa, Koshibu, Yasuoka and Hiraoka-are very large along the Tenryu river, which flows through an upheaval district. An occasional mud flow takes its rise at Mt. Hieda along the Ura river, Nagano prefecture.