March 12, 2011

Japan quake causes day to get a wee bit shorter

By SETH BORENSTEIN , AP Science Writer

Earth

You won't notice it, but the day just got a tiny bit shorter because of Friday's giant earthquake off the coast of Japan.

NASA geophysicist Richard Gross calculated that Earth's rotation sped up by 1.6 microseconds. That's because of the shift in Earth's mass caused by the 8.9-magnitude . A microsecond is one-millionth of a second.

That change in rotation speed is slightly more than the one caused by last year's larger earthquake. But 2004's bigger Sumatra earthquake caused a 6.8-microsecond shortening of the day.

The Japan quake is the fifth strongest since 1900.

Read also: Chilean Quake May Have Shortened Earth Days

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