"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.
Down the road, data from the quake will provide an unusually precise view of how Earth is deformed during massive earthquakes at sites where one plate is sliding under another, including the U.S. Pacific Northwest, scientists said.
The rich detail comes from an extensive network of sensors placed at sites across Japan after that country's Kobe earthquake of 1995, a magnitude 6.8 quake that killed more than 6,000.
"The Japanese have the best seismic information in the world," said Lucy Jones, chief scientist for the Multi-Hazards project at the U.S. Geological Survey, at a Saturday news conference at Caltech in Pasadena. "This is overwhelmingly the best-recorded great earthquake ever."
Already, just over 36 hours after the quake, data-crunchers had determined that the temblor's force moved parts of eastern Japan as much as 12 feet closer to North America, scientists said, and that Japan has shifted downward about two feet."
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