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    "en": "Landslide or Debris Flow (Earthquake Trigger)"
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      "Mass Movement,",
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    "en": "Landslide is the downslope movement of soil, rock and organic materials under the effects of gravity, which occurs when the gravitational driving forces exceed the frictional resistance of the material resisting on the slope. Landslides could be terrestrial or submarine (Varnes, 1978). <br /> <p>Varnes, D.J., 1978. Slope movement types and processes. In: Schuster, R.L. and R.J. Krizek (eds), Landslides, Analysis and Control. Special report 176: Transportation research board, National Academy of Sciences, Washington, DC. pp. 11-33.</p>"
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    "en": [
      "A landslide is the movement of a mass of rock, debris, or earth down a slope; a type of ‘mass wasting’, which denotes any down-slope movement of soil and rock under the direct influence of gravity. The term ‘landslide’ encompasses five modes of slope movement: falls, topples, slides, spreads, and flows. These are subdivided according to the type of geologic material (bedrock, debris, or earth). Slope movement occurs when forces acting down-slope (mainly due to gravity) exceed the strength of the earth materials that compose the slope (Varnes, 1978). Earthquake triggered landslides typically affect steep slopes and slopes underlain by sediments that are prone to liquefaction. Rock falls are the most abundant landslides in seismic events and occur in virtually all types of rocks on slopes steeper than 40° (Keefer, 1984). The behaviour of material on hillsides is highly dependent on the amplitudes of seismic waves that reach them, and this will vary with the epicentre distance and depth, as well as the magnitude (M) of an earthquake. Keefer (1984) from a study of historic earthquakes showed that the maximum area likely to be affected by landslides in a seismic event ranges from 0 km2 at M=4 to 500,000 km2 at M=9.2. Materials most susceptible to earthquake-induced landslide were found to include weakly cemented rocks, more indurated rocks with pervasive discontinuities, residual and colluvial sand, volcanic soils with sensitive clays (e.g., Iburi–Tobu earthquake, Hokkaido; Kameda et al., 2019), loess, alluvium and deltaic deposits. First-time slides were more common than landslide reactivation. Rock falls, rockslides, soil falls and disrupted soil slides were initiated by weak shaking; coherent deeper-seated landslides required stronger shaking; lateral spreads and flows required even stronger shaking, and rock and soil avalanches required the strongest shaking (Keefer, 1984). Within a given region, it is possible to discriminate, earthquake-triggered landslides from landslides initiated by other triggering processes. For example, Lee (2012) reported that earthquake-induced landslides in Taiwan are mostly located on steeper, longer slopes and at a higher position of the slope when compared to storm-induced shallow landslides, suggesting that topographic amplification plays an important role in earthquake-induced landslides. In hard rock terrains, earthquakes trigger a higher proportion of rock fall landslides. Zhang et al. (2014) compared earthquake-triggered landslides with rainfall-triggered landslides in the Wenchuan area of China and found that the earthquake landslides were steeper, larger landslides dominated in areas underlain by harder rocks compared with areas underlain by alluvium. In contrast, the rainfall-induced landslides were characterised by a greater volume of channelled deposits and were of a higher density but smaller area and were characterised by debris slides and debris flows. In areas that are underlain by weak rocks that are saturated, strong earthquake-induced ground shaking will result in more landslides than normal (Fan et al., 2019). Earthquake shaking and other factors can also induce landslides underwater. These are called submarine landslides. Submarine landslides sometimes cause tsunamis that damage coastal areas (Hungr et al., 2014)."
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