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Surprises surface in study of Japan quake

  |   May 19, 2011 at 7:20 PM
PASADENA, Calif., May 19 (UPI) -- U.S. researchers say newly developed models of the March 11 earthquake and tsunami in Japan reveal some surprising information about the disaster.

A study led by researchers at the California Institute of Technology, published in the May 19 issue of Science Express, combined data from earth movement measurements by Global Positioning System satellites, global seismographic networks and open-ocean tsunami recorders.

"This event is the best recorded great earthquake ever," said Mark Simons, a geophysics professor.

One of the unexpected findings of the data analysis was the spatial compactness of the event, Simons said, noting the length of the fault that experienced significant slip during the earthquake was about 150 miles, about half of what would be expected for an event of this magnitude.

Also, the area where the fault slipped the most -- 30 yards or more -- happened within a segment just 30 to 60 miles long.

"This is not something we have documented before," Simons said. "I'm sure it has happened in the past, but technology has advanced only in the past 10 to 15 years to the point where we can measure these slips much more accurately through GPS and other data."

Simons says researchers knew very little about the area, previously not thought to be a risk area for a truly large earthquake, because of limited historical data.

"Instead of saying a large earthquake probably wouldn't happen there, we should have said that we didn't know," he said.

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