Seismologists say there is a heightened risk that a major earthquake may soon strike the western coast of Sumatra as a result of the monster quake that generated the December 26 tsunami.

The Indonesian city of Banda Aceh, which was already badly hit by the killer wave, could be at risk from a quake measuring up to 7.5 on the Richter scale and there is a potential for a tsunami-making 8.5 quake offshore, they warn in a study published on Thursday in the British weekly science journal Nature.

"There is no doubt -- our calculations show a very significant increase on stress on two major active faults in the Sumatra region" since December 26, seismologist John McCloskey at Britain's University of Ulster said.

McCloskey noted that in so-called subduction zones, an earthquake can be swiftly followed by another one if certain geological conditions are met.

"There is a very well established link between these stresses and following earthquakes," he said.

Energy released by the December 26 quake has boosted stress in adjoining parts of two dangerous faults, he said.

One fault runs under land to the east of the December 26 quake and crosses the northwestern tip of Sumatra. The other fault, known as the Sunda Trench, runs under the sea to the south, parallel to the coast, where two fatal tsunamis occurred in 1833 and 1861.

"We are not trying to cry wolf," said McCloskey. "We can point to many other quakes where the stresses like the one we have measured have resulted in a following earthquake, and we are suggesting there is a significantly increased risk."

"But we are also pointing out deficiencies in our knowledge, and we cannot say there will be an earthquake in the next year or whatever. At the moment, this science I believe does not allow us to make that statement."

(China Daily March 17, 2005)