Earthquake is one of the major causes of landslides. Keefer (1984) summarized past records to classify them and also to show the maximum distance to landslides for varying seismic magnitudes. He also showed that the minimum earthquake magnitude to cause landslides is ML = 4.0 according to US records. It seems, however, that this number depends on local geology as well as the annual rainfall.
Figure 15.1 shows an overall view of a large landslide which occurred near Galdian village during the 1990 Manjil earthquake (M = 7.3) in Iran (Ishihara et al. 1992). The soil type in the slip plane was clayey as indicated by the exposed slip plane (Fig. 15.2). Some part of the sliding soil was mixed with water and formed a mud flow (Fig. 15.3). It is not uncommon that sliding mass is significantly fluidized and reaches an unexpectedly long distance.
KeywordsDebris Flow Slope Failure Excess Pore Water Pressure Turbidity Current Landslide Mass
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