Sunday, March 13, 2011

9.0 Japan earthquake shifted Earth on its axis

Scientists in Pasadena say data from the temblor will show how Earth is deformed during massive earthquakes at sites where one plate is sliding under the other, including the U.S. Pacific Northwest.

Friday's earthquake off the eastern coast of Japan was upgraded to a magnitude 9.0 by the Japan Meteorological Agency, the Kyodo News agency reported Sunday.

The agency's scientists probably had access to new data, said U.S. Geological Survey seismologist Susan Hough. "If they've upgraded, I expect USGS might follow suit," she said, adding that it was not unusual for magnitudes to move up or down by 0.1, because large earthquakes can be tricky to measure.

"It's not surgical precision," she said.

Other details are emerging. The quake probably shifted the position of Earth's axis about 6.5 inches, said Richard Gross, a geophysicist at the Jet Propulsion Laboratory in La Canada Flintridge, in an e-mail.

The temblor also should have caused Earth to rotate somewhat faster, shortening the length of the day by about 1.8 microseconds, he said.


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