The day the day changed - really
Discussion
NASA said:
The megathrust earthquake off the west coast of Indonesia on December 26, 2004,
registered a magnitude of nine on the new 'moment' scale (modified Richter scale) that indicates the size of earthquakes. It was the fourth largest earthquake in one hundred years and largest since the 1964 Prince William Sound, Alaska earthquake.
Gross and Chao 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 degrees East Longitude.
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
On a general note, the earth's rotation is slowing down due to our interaction with the moon that raises tides, the quake has offset that for a while. Quite incredible forces involved, as we might infer from the devastating consequences.
>>> Edited by turbobloke on Tuesday 11th January 16:19
As the earth's surface and upper-subsurface is made up of a series of shifting plates that lie on top of each other, its not really surprising that a large scale event such as the recent quake (they haven't really called it "megathrust" have they..? 
) will have changed the earth's shape (to me anyway)..!
What is intersting is that they have actually measured it!
) will have changed the earth's shape (to me anyway)..! What is intersting is that they have actually measured it!
Eric Mc said:
I would hazard a guess that these are theoretical predictions at present. It would take quite a while to measure the earth to see the effects of what happened only two weeks ago.
They're megathrusting everywhere these days...this is in addition to the same phrase occrring in NASA News Release 2005-009 which was my original source.
From a quick re-read, it looks like some of the data is measurement and some is prediction awaiting verification by satellite and groundstation position sensors.
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