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Quake rattled earth's orbitAdd to Clippings

AGENCIES[ TUESDAY, DECEMBER 28, 2004 09:58:37 PM ]
LOS ANGELES/AHMEDABAD: The earthquake that unleashed deadly tidal waves on Asia was so powerful it made the earth wobble on its axis and permanently altered the regional map, US geophysicists have said.

The 9.0-magnitude temblor that struck 250 km southeast of Sumatra island on Sunday may have moved small islands as much as 20 metres, according to one expert.

"That earthquake has changed the map," US Geological Survey expert Ken Hudnut said on Monday.

"Based on seismic modelling, some of the smaller islands off the southwest coast of Sumatra may have moved to the southwest by about 20 metres. That is a lot of slip."

The northwestern tip of the Indonesian territory of Sumatra may also have shifted to the southwest by around 36 metres, Hudnut said. In addition, the energy released as the two sides of the undersea fault slipped against each other made the Earth wobble on its axis, Hudnut said.

"We can detect very slight motions of the Earth and I would expect that the Earth wobbled in its orbit when the earthquake occurred due the massive amount of energy exerted and the sudden shift in mass," he said.

However, Stuart Sipkin, of the USGS National Earthquake Information Center in Golden Colorado, said it was more likely that the islands off Sumatra had risen higher out of the sea than they had moved laterally.

"In this case, the Indian plate dived below the Burma plate, causing uplift, so most of the motion to the islands would have been vertical, not horizontal."

JG Negi, an eminent seismologist who was earlier associated with the National Geophysical Research Institute, Hyderabad, tends to agree with Sipkin. "The shift would be more vertical than horizontal and would be in the range of 10 to 20 metres," he says.

Negi says such wobbling was expected as an earthquake of such magnitude would "change the natural oscillations of the earth".

These oscillations, he said, change even during the Monsoon when very large water bodies are formed. "The earth is not a steady ball and wobbling can happen during change in the movement of inertia when the mass starts moving differently with respect to the centre of the earth," he said.

In this case, he said, it was only natural that the oscillations changed with an earthquake of such great magnitude. What was more important, however, was the "thrust faulting" caused by the rift almost 1200 km long and 10 meters wide caused on the sea-bed off Sumatra. This thrust faulting would force a shifting in the islands in the vicinity.

shenbaw wrote: Oh, nope just checked.

116,000.

What's really depressing is looking back at the original article posted here.

"More than 10,000 people have been killed across southern Asia in massive sea surges triggered by the strongest earthquake in the world for 40 years."

Don't we wish. 

Red Squirrel wrote: Yeah freaky.  There's another one but I'm warning everyone it's graphic if you don't want to see dead people dont click to enlarge.