THE tsunami that devastated the coasts of Sri Lanka had taken two hours to cross the Indian Ocean, time that might have been used to sound the alarm.

But, in a region unfamiliar with the tsunami threat and without an early warning system, no alarms were issued.

Officials in the region conceded yesterday that warnings might have saved thousands of lives, but insisted that they did not know the true nature of the threat. Unlike the position in the Pacific, there is no ocean-wide warning system in place in the Indian Ocean and few of the nations with coasts have the resources to provide one.

Warnings would in any case have been pointless in Indonesian villages close to the epicentre, which were swamped within minutes. The only protection such communities can have is the knowledge that when the sea begins to drain away, it is time to run, not make for the shore to investigate.

David Booth, of the British Geological Survey, said: “The first wave tends to move away from the shore and this is actually a well-known precursor to a tsunami.

“Along the Pacific coast there are warning signs telling tourists and bathers if you see a current such as this, immediately head for the high ground,” he said. “In the Indian Ocean, these tsunamis occur with less frequency and affect less populated centres, so that there are no warning systems in place.”

Farther away from the epicentre, there was a chance of effective warnings. Waves began pummelling southern Thailand about an hour after the earthquake; in 2½ hours they had travelled 1,000 miles and slammed into India and Sri Lanka. Indonesian officials said they had no way of knowing that the earthquake had caused a tsunami or how dangerous it might be.

“Unfortunately, we have no equipment here that can warn about tsunamis,” Budi Waluyo, an official with the Indonesian Meteorology and Geophysics Agency, said. “The instruments are very expensive and we don’t have money to buy them.”

But Thammasarote Smith, a former senior forecaster at the Thailand Meteorological Department, said governments could have done much more to warn people about the danger.

“The department had up to an hour to announce the emergency message and evacuate people but they failed to do so,” Mr Thammasarote said. In the Pacific, where 80 per cent of the world’s tsunamis occur, a system has been in place since 1965, gradually increasing in sophistication. It was established after huge earthquakes in Chile in 1960 and Alaska in 1964 sent destructive tsunamis across the Pacific.

The system is served by relays of seismographs that detect and locate earthquakes within a few minutes of their occurrence. If the quake is of magnitude 6.5 or greater, and located offshore, a dangerous tsunami is possible.

The seismic information is fed into computer models that picture how and where a tsunami might form. It dispatches warnings about imminent tsunami hazards, including predictions on how fast the waves are travelling and their expected arrival times in specific places. To confirm it, tidal stations or buoys at sea are used to detect the wave. The tidal stations close to the epicentre are the first to detect the wave, and data can then be used to assess if there is a real risk.

As the waves rush past other tidal stations in the ocean, bulletins updating the tsunami warning are issued. Other models generate “inundation maps” of which areas could be damaged, and which communities might be spared. A tsunami can take up to eight hours to cross the Pacific, so there is more time to play with. The system’s co-ordination centre on Hawaii then issues warnings and it is up to governments to take action.

The system is prone to false alarms, which makes the public sceptical, but it is better than nothing.

Don McKinnon, the Commonwealth Secretary-General, called yesterday for talks on creating a global early warning system for tsunamis. He suggested that the issue could be discussed at a summit of smaller states — many of them island nations which were particularly vulnerable — being hosted by the Commonwealth on the Indian Ocean island of Mauritius next month.

Waverly Person, director of the US Geological Survey national earthquake information service in Golden, Colorado, believes that such a system could have prevented deaths. “If they had tidal gauges and a tsunami warning system, many people who died would have been saved,” he said. “They could have tracked the waves.”

That would presume , however, a communication system and widely understood procedures to clear the coastline quickly in case of a coming disaster. Most of developing Asia lacks such infrastructure, and casualties were by far highest in three highly impoverished areas: the coasts of eastern Sri Lanka and southeastern India, and the northern tip of Sumatra island in Indonesia.

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