Tsunami from Earthquakes

Indonesia TheImpossible Tsunami

By Diarmuid O'Dea

The worst disater in my lifetime occured December 26, 2004 off the coast of Sumatra, Indonesia. More than 230,000 persons died or are missing as a result of the underwater earthquake and resulting tsunami. The earthquake was the the result of the subduction of the Burma Plate under the Indian Plate. The 9.3 magnitude earthquake caused by this release of pressure was the third largest earthquake ever recorded.The death and destruction minnowed Hurrican Katrina, the 1964 Alaska Earthquake and the volcanic eruption at Mt. St. Helens. Those were all events that happened in my lifetime and left a significant imprint on me. The 2012 movie The Impossible is about that event.

A tsunami most often happens as a result of an earthquake on or below the ocean floor. Part of the ocean floor rises and disturbs or displaces the water above it which creates a significant wave or tsunami. At first the wave has a great distance between crests but as it nears land the amplitude decreases. often the tsunami will flood the land and then receeded creating a sucking sound only to return minutes later much larger. 

On the west coast of North America a large tsunami from the Cascadia Subduction Zone is entirely possible. Tsunamis could even hit North America from earthquakes on the other side of the globe. The 1946 Alaska Aleutian Earthquake was felt in Florida and caused a tsunami in Hawaii. The Indonesian earthquake and tsunami was recorded on seismometers around the world and was so powerful that it moved the entire planet 1cm.

The west coast of North America north of San Francisco is sparsely populated. Only Eureka, California and Victoria, Britsh Columbia are large population centers. The large cities: Portland, Oregon, Seattle and Vancouver, BC are either miles from the open ocean or buffeted by islands. Nevertheless, there are significant assets and many people living in harms way so that a Tsunami Warning System is an essential public infrastructure asset. 

 


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