The Hindu Business Line : When the Dec 26 quake shook the entire earth

THE earthquake that occurred on December 26 last and set off a cataclysmic tsunami that devastated several Asian nations was so powerful that no point on the Earth went undisturbed, says Dr Roger Bilham, seismologist at the University of Colorado in the US.

In a paper that has just been published in the journal Science, Dr Bilham says: "No point on Earth remained undisturbed at the centimetre level." The quake lifted the sea floor, reducing the capacity of the Bay of Bengal and the Andaman Sea thus raising the sea level around the world by 0.1 millimetre, he explains.

The quake, the second largest in the instrumental record, released energy equivalent to a 100-gigaton bomb. Rising sea floors displaced 30 cubic km of seawater that generated a tsunami that travelled as far away as the Antarctic, both coasts of the Americas and even the Artic Ocean, Dr Bilham adds.

The most remarkable feature of December's earthquake was not the initial rupture that propelled the tsunami on its destructive journey. But the fact that at the northern end of the rupture, the surface between the Indian plate and the Andaman archipelago took more than an hour to slide a distance of seven to 20 metres.

"If not for the remarkably slow plate movement at the northern end of the earthquake, there might have been much more widespread and severe damage on the coasts of India, Myanmar and Thailand," Dr Bilham points out. This experience should draw attention to the fact that conservative seismic forecasts may not serve society well, he adds.

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