Geology of a Tsunami - 1 views
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On May 22, 1960, a huge earthquake off the coast of Chile generated tsunami waves that traveled across the Pacific Ocean and reached Japan twenty-three hours later, causing damage and killing 122 people. In Chile itself, the earthquake and tsunami together killed two thousand people, injured three thousand people, and made two million people homeless.
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The outermost layer of our rocky planet is made up of a dozen tectonic plates which constantly move relative to one another at rates of one or several inches per year. The boundaries of these tectonic plates are marked by numerous active faults and earthquakes. When a fault on the ocean floor rapidly moves, it rises or collapses one block of rock against another. This creates an earthquake, disrupts the overlying water, and sends fast moving tsunami waves. Although large undersea earthquakes and water-column displacements are responsible for most tsunamis, there have been tsunami events in which the earthquake occurred on islands or near the coastal areas. It is thus possible that seismic (earthquake-generated) waves traveling along the Earth's surface also play a role in tsunamis, propagating energy from rocks to ocean water.
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All along the margin of the Pacific Ocean, there are subduction zones where the denser oceanic plate descends under the lighter continental plate. This has created the Ring of Fire--a circum-Pacific belt of numerous volcanic eruptions and earthquakes. Almost 80 percent of tsunamis in the world take place in the Pacific Ocean. However, there are subduction zones in the Indian Ocean and in the Caribbean Sea too; these regions are prone to earthquakes and tsunamis as well. Destructive tsunamis are usually generated by undersea earthquakes with magnitudes exceeding 7 on the Richter scale.
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Article describing how a tsunami works, how they are measured and the new technology, and what to watch for.
