COMPARISON OF TSUNAMI WAVES GENERATED BY METEORITE IMPACTS AND LANDSLIDES

Tsunamis can be generated by a variety of different processes. Earthquakes are among the most frequent causes of tsunamis and their destructive power was recently demonstrated by the catastrophic events in Japan 2010 and Sumatra 2004. It can only be speculated about the frequency of tsunamis due to submarine slope failure as they take place often undetected, and evidence of their occurrence is yet to be discovered. However, the frequency of such events is expected to be very high. In contrast to tsunamis from earthquakes submarine slope failures produce relatively short waves (wave periods up to minutes; earthquakes generate waves typically on the order of 30 min) with amplitudes that can be up to two orders of magnitude higher in the generation area. The wave characteristic of landslide-generated waves has much more in common with tsunamis that originated from the strike of a cosmic object in an ocean. With respect to likelihood of recurrence intervals meteorite impacts occur much less frequent but generate waves that are several orders of magnitude higher than waves caused by any other mechanism. We employ numerical modelling to simulate the wave characteristics generated by the Eltanin impact, which occurred 2.5 Ma years ago in the Bellinghausen Sea, South Pacific and compare the results with a suite of simulations of landslides. We varied important controlling parameters that affect the wave characteristic such as slide rheology and mass, slope angle, and water depth. In both cases the initial waves show dispersive and highly nonlinear effects in the near field (close to origin). In comparison to earthquakes the generated waves are very steep, decay relatively quickly, and may break during shoaling far away from the coastline. These facts lead us to the conclusion that waves generated by submarine mass failures and meteorite impacts cannot reach the coastline with destructive power that are thousands of kilometers away; they cannot have a global reach like the 2004 Sumatra tsunami had. However, the consequences for coastal regions nearby the generation area are much more severe due to the much larger wave amplitudes.