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Effects of Indian Ocean earthquake on the Earth

Here is a nice little summary of these effects [via, believe it or not, More Junkmail from Bob]:

[Dr. Benjamin Fong] Chao [of NASA's Goddard Space Flight Center, Greenbelt, MD] and [Dr. Richard] Gross [of NASA's Jet Propulsion Laboratory, Pasadena, CA] have been routinely calculating earthquakes' effects in changing the Earth�s rotation in both length-of-day as well as changes in Earth�s gravitational field. They also study changes in polar motion that is shifting the North Pole. The "mean North pole" was shifted by about 2.5 centimeters (1 inch) in the direction of 145°ree; East Latitude. This shift east is continuing a long-term seismic trend identified in previous studies.

They also found the earthquake decreased the length of day by 2.68 microseconds. Physically this is like a spinning skater drawing arms closer to the body resulting in a faster spin. The quake also affected the Earth�s shape. They found Earth�s oblateness (flattening on the top and bulging at the equator) decreased by a small amount. It decreased about one part in 10 billion, continuing the trend of earthquakes making Earth less oblate....

The researchers concluded the Sumatra earthquake caused a length of day (LOD) change too small to detect, but it can be calculated. It also caused an oblateness change barely detectable, and a pole shift large enough to be possibly identified. They hope to detect the LOD signal and pole shift when Earth rotation data from ground based and space-borne position sensors are reviewed.

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