http://www.cnn.com/2010/WORLD/americas/03/02/chile.quake/index.html?hpt=T1

March 2, 2010 8:24 a.m. EST

*(CNN)* -- The massive earthquake that struck Chile on Saturday may have
shifted the Earth's axis and created shorter days, scientists at NASA say.

The change is negligible, but permanent: Each day should be 1.26
microseconds shorter, according to preliminary calculations. A microsecond
is one-millionth of a second.

A large quake shifts massive amounts of rock and alters the distribution of
mass on the planet.

When that distribution changes, it changes the rate at which the planet
rotates. And the rotation rate determines the length of a day.

"Any worldly event that involves the movement of mass affects the Earth's
rotation," Benjamin Fong Chao, of NASA's Goddard Space Flight Center in
Greenbelt, Maryland, said while explaining the phenomenon in 2005.

Scientists use the analogy of a skater. When he pulls in his arms, he spins
faster.

That's because pulling in his arms changes the distribution of the skater's
mass and therefore the speed of his rotation.

Richard Gross, a geophysicist at NASA's Jet Propulsion Laboratory in
Pasadena, California, used a computer model to determine how the magnitude
8.8 quake <http://topics.cnn.com/topics/Earthquakes> that struck Chile on
February 27 may have affected the Earth.

He determined that the quake should have moved the Earth's figure axis about
3 inches (8 centimeters). The figure axis is one around which the Earth's
mass is balanced. That shift in axis is what may have shortened days.

Such changes aren't unheard of.

The magnitude 9.1 earthquake in 2004 that generated a killer
tsunami<http://topics.cnn.com/topics/Tsunamis>in the Indian Ocean
shortened the length of days by 6.8 microseconds.

On the other hand, the length of a day also can increase. For example, if
the Three Gorges reservoir in China were filled, it would hold 10 trillion
gallons (40 cubic kilometers) of water. The shift of mass would lengthen
days by 0.06 microsecond, scientists said.


-- 
I've got nothing against God.  It's his fan club I can't stand.

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