NJG86-3-11
2006
Mechanisms of tsunami generation by submarine landslides: a short review
86
3
pp. 255-264
82-92394-30-3

The characteristics of a tsunami generated by a submarine landslide are mainly determined by the volume, the initial acceleration, the maximum velocity, and the possible retrogressive behaviour of the landslide. The influence of these features as well as water depth and distance from shore are discussed. Submarine landslides are often clearly sub-critical (Froude number <<1), and it is explained that the maximum tsunami elevation generally correlates with the product of the landslide volume and acceleration divided by the wave speed squared. Only a limited part of the potential energy released by the landslide is transferred to wave energy. Examples of numerical simulations with fractions of 0.1-15 % are presented. Frequency dispersion is of little importance for waves generated by large and sub-critical submarine landslides. Retrogressive landslide behaviour normally reduces associated tsunami heights, but retrogression might increase the height of the landward propagating wave for unfavourable time lags between release of individual elements of the total landslide mass. Tsunamis generated by submarine landslides often have very large run-up heights close to the source area, but have more limited far-field effects than earthquake tsunamis. It is further shown that the combination of landslides and earthquakes may be necessary to explain observed tsunami behaviour. The various aspects mentioned above are exemplified by simulations of the Holocene Storegga Slide, the 1998 Papua New Guinea, and the 2004 Indian Ocean tsunamis. Comparisons are also made to tsunamis generated by rock slides. Rock slides are most often super-critical and the resulting tsunamis are determined by the frontal area of the rock slide, the impact velocity of the rock slide on the water body, the permeability of the rock slide, and the bathymetry

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