The size of each circle represents the magnitude of the associated quake or shock.
The massive earthquake that struck northeast Japan Friday (March 11) has shortened the length Earth's day by a fraction and shifted how the planet's mass is distributed.
More refinements are possible as new information on the earthquake comes to light, he added.
The closer the mass shift during an earthquake is to the equator, the more it will speed up the spinning Earth.
The earthquake also shifted Earth's figure axis by about 6 1/2 inches (17 centimeters), Gross added.
The 8.8-magnitude earthquake in Chile last year also sped up the planet's rotation and shortened the day by 1.26 microseconds.
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