The main shock (M=7.0), occurred in near Izu-Oshima Island on January 14, 1978, caused the violent disaster in central part of Izu peninsula.
Disasters were found out in roads, railways and buildings. Slope failures occurred remarkably in the area.
A total number of slope failure was awfully counted as about six hundred and twenty, and the greater part of slope failure occurred on near mountain ridge, that is, near slope changing line. Half number of failures was 20-40 meter in height and 10-20 meter in width as shown in Fig. 1 and 2. Geology of failure site was mainly tertiary and andesitic lava, and a few failure occurred in scoria and volcanic mud flow as shown in Fig. 10.
Failures taked place along the earthquake fault by the shock and coincided with after shocks as shown in Fig. 12.
The ratio of failure area is about 6% near the earthquake fault and about 0.1% farther than 5 kilometer away from the fault.