VI: Tsunamis

[Info from: http://www.prh.noaa.gov/pr/ptwc/abouttsunamis.htm]

A tsunami, also known as a seismic sea wave, can be generated by submarine volcanic eruptions, by displacement of submarine sediments, by coastal landslides into a bay or harbor, by meteor impact, or by vertical displacement of the earth's crust along a zone of fracture which underlies or borders the ocean floor. The latter is by far the most frequent cause of tsunamis and for all practical purposes the primary cause of tsunamis capable of propagation across an ocean basin.

Tsunamis can occur in any ocean region, but most are located in the Pacific Ocean because of the higher frequency of earthquakes in that region. Tsunamis can be categorized as local, regional, or Pacific-wide, with those terms being used to describe the extent of potential destruction relative to the tsunami source area. Regional tsunamis are by far the most common. Pacific-wide tsunamis are much less frequent, but of far greater destructive potential in that waves are not only larger initially, but in transit across the Pacific basin, many distant coastal areas are subject to destructive impact.

Tsunami earthquakes usually have a shallow focus with a slower than normal slippage along the fault.

[ Location of Tsunami warning systems in the Pacific Ocean ]

Speed of Tsunamis

In the middle of the ocean, a tsunami is relatively shallow at the surface, however, as it reaches the shore, the height greatly increases. The energy of the wave extends to the bottom of the ocean, so when it reaches the shallow shore, the energy contained in the wave forces a huge increase in height.

Tsunamis can travel across the entire Pacific Ocean in one day.

[ tsunami speed image ]

Two simulations of tsunamis:

[ Animation:http://www.pmel.noaa.gov/tsunami/Mov/andr1.mov ]

[ Animation:http://www.pmel.noaa.gov/animations/Aonae.all.mpg ]

Damage of Tsunamis

Pictures of tsunami damage:

  
[ image 1 ]

[ image 2]

  
[ image 3]