August 27 2008
Lecture 8 Outline Earthquakes/Tsunamis
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MAR110 LECTURE #8 Earthquakes and Tsunamis
Figure 8.1 Tsunami Generation Mechanisms The two main causes of tsunamis are underwater earthquakes/faulting (left) and landslides (right). Both have the capacity to displace the large volume of water necessary to generate a tsunami. (NG)
Figure 8.2 Underwater Faulting & Sea Surface Distortion The underwater faulting illustrated above causes vertical displacement of the whole column of water above it converting the kinetic energy of the faulting process - initially into the potential energy of a solitary wave. The energy in the solitary wave radiates outward from the generation site forming a circular wave front (?)
27 August 2008
Lecture 8 Outline Earthquakes/Tsunamis
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Figure 8.3 The 26 December 2004 Sumatra Tsunami The circular wave front of the Sumatra tsunami propagates throughout the Indian Ocean striking various coastal regions hours after its generation. The differing wave heights at the different locations often reflect different wave shoaling conditions. (NG Apr05)
Figure 8.4 Tsunami Evolution Tsunami waves are barely perceptible, as they propagate in the open ocean because the sea surface slopes are so small. However as the water shoals the wave fronts steepen considerably.
27 August 2008
Lecture 8 Outline Earthquakes/Tsunamis
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Figure 8.5 Sumatra Tsunami Evolution: First 30 Minutes The progression of the 2004 Sumatran tsunami showing the initial displacement (exaggerated) due to the undersea faulting; the wave front propagates at the speed of a jet airliner toward the nearest coast Banda Aech, Sumatra. (NG )
Figure 8.6 Tsunami Shoaling The height of a tsunami grows dramatically as it comes a shore. Usually the water at the shore first recedes to feed the growth of the offshore tsunami wave.
27 August 2008
Lecture 8 Outline Earthquakes/Tsunamis
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Figure 8.7 Tsunami Leading Trough Landfall - Chile 1868 (above). Ships are left high and dry during the minutes preceding landfall the of the Chilean tsunami of 1868. Minutes later the ships were being tossed around by a chaotic ocean. (below) Note the comparison of a 60ft (20m) wave and a 6-story high ship.
27 August 2008
Lecture 8 Outline Earthquakes/Tsunamis
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Figure 8.8 Tsunami Cresting The wave crests with heights ranging from a few 10s to 100s of feet (or 5 to 50 meters). The wave then breaks - followed by the inundation of the turbulent water comes ashore. Depending upon the slope of the coastal region, the tsunami wave can flood the coast up to miles inland. (ItO)
Figure 8.9 Tsunami Coastal Flooding This sequence of photos shows a relatively small tsunami hitting a Hawaiian beach. (NH)
27 August 2008
Lecture 8 Outline Earthquakes/Tsunamis
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Figure 8.10 Sumatra Tsunami Landfall The 12/26/2004 tsunami as it makes landfall on a stretch of coastline. (NG)
Figure 8.11 Satellite Pictures Record Sumatra Tsunami Impact Banda Aceh, Indonesia both before (left) and after (right) the 12/26/2004 tsunami. Note the destruction of fields and vegetation as well as the flooding. (NG)
27 August 2008
Lecture 8 Outline Earthquakes/Tsunamis
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Figure 8.12 Chilian Earthquake/Tsunami 1960 In 1960 the largest recorded eart...