Tsunami, Earthquakes, Hurricanes, Volcanic Eruptions and other Natural and Man-Made Hazards and Disasters - by Dr. George Pararas Carayannis

 

Tsunami, Earthquakes, Hurricanes, Volcanic Eruptions and other Natural and Man-Made Hazards and Disasters

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TSUNAMIGENIC EFFICIENCY OF VOLCANICALLY, SEISMICALLY AND GRAVITATIONALLY INDUCED ISLAND EDIFICE MASS FAILURES AND OF AERIAL AND SUBMARINE LANDSLIDES

George Pararas-Carayannis

Abstract of poster presentation prepared for the 32nd International Geological Congress, (T11.15 (115) Tsunami hazard from slope instability), Florence, Italy, August 20-28, 2004

ABSTRACT

Short and longer period impulsive waves can be generated in the open ocean - or in confined bodies of water - by a variety of volcanic island edifice mass failures and by volcanically, seismically or gravitationally induced aerial or submarine landslides and  rock falls.

Regardless of the nature of the triggering event, the kinematic processes of volcanic mass edifice failures and of submarine landslides are complex phenomena and result in different types of impact interaction with the water mass.

The resulting mechanisms of wave generation and their tsunamigenic efficiency depend on the nature, speed and energy of the triggering source event. Additional factors are the volume and physical dimensions of the water displacing mass, the type of slide, the spatial coherency or deformation of the slide flow or rotation, the elongational and shear strain of the slide, the frictional effects of adjacent geologic formations, the hydrodynamic impact on initial and subsequent water crater formations and water surface deformations, as well as the resulting water vorticity, turbulence, geometrical spreading, divergence and wave height attenuation. 

Flank instability of Kilauea volcano on the island of Hawaii. Hawaii's southern slope showing coastal faults parallel to the east rift zone of the Kilauea volcano, and the Hilina Slump along which slope failures have been occurring (Modified after Morgan et al. 2001).


Impulsively generated waves from such complex source mechanisms can be expected to behave non-linearly and to change significantly away from the sourceregion, with varying near and far field effects and terminal run up heights.

Evaluation of such processes for several historic events, leads to the conclusion that volcanic edifice mass failures, impact rock falls and submarine landslides have the potential of generating destructive local waves in confined bodies of water and in the near field environment of an open ocean coast. However the heights of these waves attenuate rapidly with distance because of relatively smaller source dimensions and shorter wave periods.

Specifically evaluated for their tsunamigenic efficiency are the mechanisms of past massive submarine landslides and of flank failures of island stratovolcanoes in the Hawaiian Islands, in the Caribbean and Mediterranean Seas, and in the Atlantic and Indian Oceans.

 

 

 

 

Flank instability of Cumbre Vieja volcano on the island of La Palma. Relief Map of the island of La Palma in the Canary Islands showing the volcanoes of Taburiente, Cumbre Nueva Cumbre Vieja and the north-south trending rift zone and secondary faults.

Flank instability of the Piton De La Fournaise volcano on Reunion Island Reunion Island in the Indian Ocean and the Piton De La Fournaise volcano showing extensive erosion, subsidence and an arcuate coastline suggestive of underwater slope failure.(Source: GEOSAT photos)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Map of the Island of Vulcano in Italy where a 200,000 cubic meter massive flank failure on the northeast side generated local tsunami

 

 

 

 

 

 

 

 

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