Thursday, March 4, 2010

How Chile's quake may possibly have shortened a day?

NASA scientists consider Chile's devastating earthquake may have speeded up the Earth's rotation and shortened the length of a day.

Researcher Richard Gross and his colleagues at NASA's Jet Propulsion Laboratory in California intended that Saturday's 8.8-magnitude quake could have cut 1.26 microseconds off the length of a day. Not that anyone would observe however - as that's one-millionth of a second.

How an earthquake could shorten a day explained below:

The Earth is not a perfect sphere. It is strained in slightly at the poles and bulges at the equator. As such, it rotates with a wobble just similar to a spinning top. However, changes in the distribution of mass can influence this spin. This is shown in the following figure:

In the same way a skater speeds up a spin by pulling in their limbs, a quake can make the Earth rotate quicker by nudging some of its mass closer to the planet's axis. Movements in atmosphere and oceans can have a related effect. This is shown in the following figure:

NASA calculates the quake in Chile shifted mass to such an extent that it altered the rotation rate to shorten a day by about 1.26 microseconds, or one millionth of a second. This is shown in the following figure:

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