Seismic shifts caused by the December 26 earthquake under the Indian Ocean may lead to another quake and devastating tsunami soon, warn scientists from the University of Ulster in Coleraine.

The scientists, led by seismologist John McCloskey, say last year's earthquake put dangerous levels of stress on vulnerable parts of the fault zone, significantly raising the chances of a magnitude 7.5 earthquake in two specific areas, particulary in the Sumatra region.

'Seismologists have studied the fault lines around the Burma microplate, whose border with the Indian plate was the scene of the huge jolt in December 2004. Using a mathematical model, they conclude that the increased strain on the neighbouring Sumatra fault, which runs through the island itself, makes Sumatra the most likely place for a subsequent earthquake,' said Nature magazine.

In their report, they say that while they cannot accurately predict when such an earthquake may occur, earlier "coupled" earthquakes have struck within a year of each other.

"Many of us are brought up to understand hazard as whenever you've had your bit of bad luck it doesn't happen again. Lightning never strikes twice. But one great indicator that you're going to have an earthquake is that you've just had one," The Guardian, London [Images], quoted McCloskey as saying.

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"These are very significant and extensive increases in stress. We cannot say for certain it will result in an earthquake but it's the biggest stress increase over a large area that we've measured since we started doing this research."

According to The Guardian, 'the new study shows one of the regions at increased risk of a more powerful event is a 31-mile stretch of the undersea Sunda trench, next to the 745-mile long zone that ruptured on Boxing Day. Earthquakes in the Sunda trench triggered fatal tsunamis in 1833 and 1861.

'The second area of concern identified in the new research is a 185-mile region of fault running directly beneath the island of Sumatra, close to the city of Banda Aceh, which was devastated in December and where rebuilding work is under way.

'The scientists estimate that stress in the Sunda trench region has increased by up to 5 bars; in the Sumatra fault it has been forced up by as much as 9 bars,' The Guardian said.

A tsunami triggered by the Sunda trench would mostly dissipate in the Southern Ocean, McCloskey told news@nature.com.

'But Indonesia, particularly Sumatra, would almost certainly be struck again, and the wave would probably wash up on southern African shores too.'

Stressing the urgency of installing a tsunami warning system in the Indian Ocean, he said: "People think 'well you've had your bad luck', but earthquakes cluster in time and in space."