Tsunami Earthquake 'Unzipped' the Earth

The great Sumatra-Andaman earthquake of Dec. 26"unzipped" an 800-mile stretch of the planet and released twice the energy first thought; it also bowed Earth like a gigantic cello string, a series of studies say.

The remarkable geophysical effects of the terrible quake were explored in several research papers in the May 20 issue of the journal Science.

First consider the unzipping: Instead of just rupturing at one point underground and being followed by aftershocks around that point, the 9-plus magnitude quake set off a series of ruptures from Banda Aceh northward, taking anywhere from seconds to hours to unevenly push up different locations 17 to 50 feet. 

"A huge amount of real estate was slipping," said geophysicist Jeffrey Park of Yale University, who specializes in studying how the Earth has been literally ringing from the quakes ever since.

"The earthquake was somewhat unprecedented in our history of trying to understand earthquakes," said Thorne Lay, chairman of the Incorporated Research Institutions for Seismology (IRIS) and a seismologist at the University of California at Santa Cruz.

Continuing study of the quake is revealing that some 25 to 35 percent of the quake movement happened from an hour to three hours after the main shocks.

Looking at data from a range of worldwide sources GPS stations, seismometers and even satellites scores of international researchers have been able to put together an unprecedented and increasingly coherent picture of what happened that awful day.

"It did go on for longer than other quakes," said Lay.

So much longer and with so much movement that the mathematical tools used by seismologists to extract and decipher the seismic waves "gagged on this thing," he said.

Some fast revamping of those tools prepared researchers for the second big shock: an 8.7 magnitude earthquake on March 28. This last quake was centered southeast of the Dec. 26 epicenter, on the connected segment of the subduction zone that had not ruptured since 1861.

 Copyright 2005 Discovery Communications Inc.  

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