Journal of the Japan Society of Erosion Control Engineering, Vol.64,No.3, 2011

### Study on area ratio of slope failures triggered by Earthquake -Examination
by the 2007 Noto-Hantou Earthquake-

Setsuo HAYASHI, Toshiyuki ARAKI, Takashi YAMADA, Shinya NUMAMOTO

Abstract

Earthquake acceleration is the main factor of slope failure triggered by an
earthquake. This study investigated the relationship between the area ratio
of slope failure and slope angle as well as geological properties in a 294km2rectangular
compartment in a seismic zone off the coast of Kurosaki in Noto Kongo]kita,
which was directly above the epicenter of the 2007 Noto]Hantou Earthquake. Because
sufficient research has not been conducted to evaluate the area ratio of slope
failure using the individual factors of soil strength, earthquake acceleration,
and slope angle, we propose employing the slope unstability index (Skf), which
is comprised of a slope angle factor, geological properties (cohesion and failure
weight), and earthquake acceleration. GIS analysis revealed that geology determines
the relation between slope angle and area ratio of slope failure (Sa);specifically,
the soil strength of the slope is an important factor for slope failures triggered
by an earthquake. Hence, the area ratio of slope failure is strongly governed
by the slope unstability index (Skf).

Key wordsFNoto]Hantou Earthquake, Geological property, Slope angle, Acceleration,
Area ratio of slope failure, Slope unstability index

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