It decreased about one part in 10 billion, continuing the trend of earthquakes making Earth less oblate. They found Earth's oblateness (flattening on the top and bulging at the equator) decreased by a small amount. The quake also affected the Earth's shape. Physically this is like a spinning skater drawing arms closer to the body resulting in a faster spin. They also found the earthquake decreased the length of day by 2.68 microseconds.
This shift east is continuing a long-term seismic trend identified in previous studies. The "mean North pole" was shifted by about 2.5 centimeters (1 inch) in the direction of 145 degrees East Longitude. They also study changes in polar motion that is shifting the North Pole. 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. "Any worldly event that involves the movement of mass affects the Earth's rotation, from seasonal weather down to driving a car," Chao said. It's just they are usually barely noticeable. Benjamin Fong Chao, of NASA's Goddard Space Flight Center, Greenbelt, Md., said all earthquakes have some affect on Earth's rotation. Richard Gross of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and Dr.
The earthquake that created the huge tsunami also changed the Earth's rotation. NASA scientists using data from the Indonesian earthquake calculated it affected Earth's rotation, decreased the length of day, slightly changed the planet's shape, and shifted the North Pole by centimeters.
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