Earth 'wobbled' after quake

2004-12-28 09:13

Los Angeles - An 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, United States geophysicists said on Monday.

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

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

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

Earth 'wobbled'

The northwestern tip of the Indonesian territory of Sumatra may also have shifted to the southwest by around 36m, 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," Hudnut said.

Another USGS research geophysicist agreed that the earth would have got a "little jog," and that the islands off Sumatra would have been moved by the quake.

However, Stuart Sipkin, of the USGS National Earthquake Information Centre 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 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."

The tsunamis unleashed by the fourth-biggest earthquake in a century have left at least 23 675 people dead in eight countries across Asia and as far as Somalia in East Africa.

The tsunamis wiped out entire coastal villages and pulled beach-goers out to sea.

The International Red Cross estimated that up to one million people have been displaced by the natural calamity. - AFP

- SAPA