Soil-Slide Avalanches of Pyroclastic Fall Deposits Induced by the 2011 Off the Pacific Coast of Tohoku Earthquake

Characteristics of landslides in forests and grasslands triggered by the 2016 Kumamoto earthquake

“…In general, landslides in relatively ‘soft’ soils, such as volcanic ash, occur on relatively gentle slope gradients (e.g. Hotta et al, ; Tanaka, ; Okusa et al, ; Chigira et al, ; Song et al, ). Indeed, 59% of the landslides identified in our study occurred on slopes < 30° (Figure ).…”

“…Among 54 landslides triggered by the 2008 Wenchuan earthquake, the horizontal travel distance ranged from 347 to 4170 m (Guo et al, ). Chigira et al () showed that the travel distance of four landslides caused by the 2011 Tohoku earthquake (Mw = 9.0) ranged from 143 to 330 m, with a mean distance of 264 m (SD: 77 m) in regions underlain by pyroclastic fall deposits. Fujita and Suzuki () reported that landslides caused by the 1984 west Nagano earthquake were displaced 500–1000 m due to liquefaction on volcanic hillslopes of Mt Kiso Ontake, Japan.…”

Geological and geomorphological features of deep-seated catastrophic landslides in tectonically active regions of Asia and implications for hazard mapping

“…The paleosol, which had been formed by the leaching out of silica, alkali, and alkaline earth elements, reacted with percolating rainwater that had obtained silica during its infiltration through the new deposits, then resilicified and formed halloysite. This process is understood to be the primary reason for the occurrence of halloysite in these buried paleosols (Chigira, 1982;Kleber et al, 2007;Chigira et al, 2014). Similar landslides involving a sliding surface in a paleosol have occurred during many other earthquakes (Table 2), including the 2009 Padang earthquake.…”

“…On the basis of our studies on the geological and geomorphological features of catastrophic rock and debris-slide avalanches in Asian countries, I have reached the conclusion that it is possible to predict at least the potential sites of such events. Most of the catastrophic rock-slide avalanches induced by either rainstorms or earthquakes are preceded by a particular type of gravitational slope deformation (Chigira, 1992;Dramis and Sorrisovalvo, 1994;Kilburn and Petley, 2003;Crosta et al, 2006;Chigira, 2009), whereas debris-slide avalanches caused by earthquake-induced failure of pyroclastic fall deposits are not (Chigira, 1982;Chigira et al, 2014). The latter, however, occur in areas of a particular type of pyroclastic succession characterized by heavily weathered pyroclastics or paleosol(s) at depth.…”