WASHINGTON — The Sumatra-Andaman earthquake that generated the devastating tsunami in December was so powerful that the ground shook everywhere on the Earth's surface and weeks later the planet still trembled.

"No point on Earth remained undisturbed," said Roger Bilham of the University of Colorado.

Ground movement of at least 0.4 inch occurred everywhere as a result of the strongest quake in more than 40 years, although the sensation was not noticed in many areas.

The quake resulted from the longest fault rupture ever observed: 720 miles to 780 miles, which spread for 10 minutes. A typical earthquake lasts 30 seconds.

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

A special section of a half-dozen research papers on the quake appears in today's issue of the journal Science.

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At that spot, the Eurasian plate was being pulled downward by the descending Indo-Australian plate. The quake released the edge of the Eurasian plate, which sprang up, lifting the ocean floor and sending the sea water off in the giant wave, the researchers reported.

They said the higher seafloor displaced so much water from the Bay of Bengal and the Andaman Sea that sea level worldwide was raised by 0.004 inch.

The temblor also "delivered a blow to our planet" that was felt for weeks, according to a team of researchers led by Jeffrey Park of Yale University.

His group calculated that the quake caused the planet to oscillate like a bell, at periods of about 17 minutes, which scientists were able to measure for weeks afterward.

The initial quake off Sumatra on Dec. 26 is estimated to have had a magnitude of 9.1 to 9.3. A second quake to the south March 28 registered 8.6.