Quake warning bells ring

LONDON - The devastating earthquake that triggered the Boxing Day tsunami has raised the likelihood of another major eruption in the region, scientists say.

It put more stress on other active faults in the area, making another earthquake with a magnitude of up to 7.5 far more likely and increasing the need for a warning system.

"The implications of our work show very clearly that earthquake hazard in this area continues to be high," said John McCloskey of the University of Ulster.

"There is a folk understanding that lighting doesn't strike twice in one place - but earthquakes do," he said.

Although it is difficult to predict when another might occur, previous coupled earthquakes in Japan happened within a few years of each other.

Quakes happen when the Earth's tectonic plates collide.

About 300,000 people perished in the tsunami that followed the magnitude 9 undersea earthquake on December 26 last year. An estimated 1200km of faultline slipped up to about 20m along the subduction zone where the India Plate dives under the Burma Plate.

"It is absolutely phenomenal from a seismological point of view," said McCloskey, who reported the findings in the science journal Nature.

The two plates come together at an area called the Sunda trench.

Previous earthquakes on the Sunda trench set off fatal tsunamis in 1833 and 1861.

Stress builds up because of the movement of plates. The displacement changes the stress values for hundreds of kilometres. McCloskey and his colleagues calculated there was an increase of up to 5 bars (a unit of stress or pressure) in the 50km of the Sunda trench next to the rupture zone and up to 9 bars for about 300km on the Sumatra fault near Banda Aceh.

"It is one of the biggest increases in stress I've seen in the years I have been working with this," said McCloskey.

The Izmit earthquake in Turkey that measured 7.4 was triggered by stress increases of less than 2 bars, according to the researchers.

Professor Peter Styles, president of the Geological Society in Britain, said every effort should be made to ensure monitoring technologies and communication protocols were put in place to monitor the Indian Ocean.

McCloskey also emphasised the need for a warning system.

"The tsunami warning system is very important," he said.

"We can't stop the earthquake but we could mitigate many of its effects if we do this quickly."

- REUTERS