Sumatra Quake Shook Entire Earth

New Technology Reveals True Strength of Tremor

(AP)  December's great Sumatra-Andaman earthquake — the most powerful in more than 40 years and the trigger of a devastating tsunami — shook the ground everywhere on Earth's surface. Weeks later the planet was still trembling.

The quake resulted from the longest fault rupture ever observed--720 miles to 780 miles--which spread for 10 minutes, also a record. A typical earthquake's duration would be 30 seconds.

The December quake was the first of its size to be measured and studied by the new worldwide array of digital seismic instruments.

Those results are starting to come in, with a special section of a half-dozen research papers on the quake appearing in Friday's issue of the journal Science.

"This is really a watershed event. We've never had such comprehensive data for a great earthquake because we didn't have the instrumentation to gather it 40 years ago," said Thorne Lay, professor of Earth sciences and director of the Institute of Geophysics and Planetary Physics at the University of California, Santa Cruz.

"It is nature at its most formidable," Lay said in a statement.

The earthquake and resulting tsunami, which swept across the Indian Ocean, killed more than 176,000 people in 11 countries and left about 50,000 missing and hundreds of thousands homeless.

The quake occurred where two of the giant plates that form the surface of the Earth grind together.