January 10, 2005: NASA scientists studying the Indonesian earthquake of Dec. 26, 2004, have calculated that it slightly changed our planet's shape, shaved almost 3 microseconds from the length of the day, and shifted the North Pole by centimeters.
Dr. Benjamin Fong Chao of NASA's Goddard Space Flight Center and Dr. Richard Gross of NASA's Jet Propulsion Laboratory said all earthquakes have some effect on Earth's rotation. It's just that the effects are, usually, barely noticeable.
This one was not usual: The devastating megathrust earthquake registered nine on the new "moment" scale (modified Richter scale), making it the fourth largest 'quake in one hundred years.
Chao and Gross routinely calculate earthquakes' effects on Earth's shape and rotation. They also study changes in polar motion--that is, the shifting of the North Pole.
According to their latest calculations, the Dec. 26th earthquake shifted Earth's "mean North Pole" by about 2.5 centimeters (1 inch) in the direction of 145 degrees east longitude, more or less toward Guam in the Pacific Ocean. This shift is continuing a long-term seismic trend identified in previous studies.