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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS002 Oral Presentation 1745
Mega-tsunami of the world ocean: did they occur in the recent past
Dr. Viacheslav Gusiakov
Department of Geophysics Inst. of Compl Mathematics and Math. Geophysics IASPEI
Abbott Dallas, Bryant Edward, Masse Willliam
The comprehensive historical tsunami database collected at the Novosibirsk Tsunami Laboratory,
contains data on more than 2250 historical events occurred in the World Ocean from 1628 BC to
present. Even if the historical data set is obviously incomplete for many areas, especially for older times,
the world catalog contains enough data to estimate an average run-up heights for the largest
seismically-induced tsunamis resulted in wide-spread damage and large number of fatalities (1755
Lisbon, 1868 and 1877 Chile, 1952 Kamchatka, 1957 Aleutians, 1960 Chile, 1964 Alaska, 2005
Sumatra). This average run-up does not exceed 30-35 meters on the nearest coast with 10-12 meters
at the distance more than 5000 km. Somewhat larger waves (up to 40-45 m) can be generated by
volcanic explosions followed by volcanic cone collapse (Santorini 1628 BC, Kuwae 1453, Unzen 1792,
Tambora 1815, Krakatau 1883). Landslide-generated tsunamis have the largest recorded heights (up to
525 m) but normally these events are very local with the width of inundated area from hundred meters
to several kilometers (1958, 1936, 1853 Lituya Bay, 1936 Norway, 2000 Greenland). Meanwhile, many
parts of the World Ocean coastline contain the prominent features of catastrophic impact of water
currents and waves that came from the ocean. They are large boulders, weighing well above one
hundred tons, lying on the top of vertical cliffs at the height up to 60 m and large vortexes cut-down in
rather resistive coastal rocks. On a smaller scale, these features include sculptured bedrocks, grooves,
canyons, cavettos and flutes, found in areas where hurricanes and severe tropical storms are not
common. Sedimentational features of water impacts include mega-ripples found in the north-western
Australia and so-called chevrons (parabolic and blade-like sand dunes) that are common along many
parts of the Indian Ocean coast. In southern Madagascar, chevrons reach altitude of 205 m with 30-35
km in-land penetration. The high energy water flux of that scale could be generated by Storegga-class
submarine landslides or Santorini-class volcanic explosions, but for this area does not have nearby
active volcanoes or large sedimentation basins having potential for large-volume submarine sliding. Not
widely acknowledged presently, but still real possibility is creating of these coastal features by
catastrophic oceanic waves generated by deep-water impacts of large comets or asteroids. In the Indian
Ocean, several crater candidates (Burckle, Mahuika, Kukla, Flinders) have been found recently by
geomorphological analysis of detailed bathymetric maps They are geologically young and analysis of
nearby deep-sea cores shows the presence of some elements and minerals typical for oceanic impact
structures. The paper discusses the consistency of these data with spatial and azimuthal distribution of
the large-scale erosional and sedimentational features found at the Australian and Madagascar coast.
Keywords: tsunami, run up, impacts