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  The Straits Times, 16 Jan 05
The next big one
by Chua Kong Ho

IF THE Dec 26 undersea earthquake was a staggering jolt, a bigger monster could be lurking just south of it, said scientists interviewed by The Sunday Times.

Studies on past earthquakes indicate the undersea quake off Sumatra is a threat that is likely to rear its head in the next few decades and possibly as soon as 30 years. However, where and when it will strike is hard to predict, the experts said. When it does, the deadly tsunamis it triggers are expected to spread further and slam into coastal populations as far south as Australia and eastwards to Africa.

Which is why a tsunami warning system in the Indian Ocean needs to be set up as soon as possible, Professor Asish Basu, an earthquake expert at New York's University of Rochester, told The Sunday Times.

But that is not enough. Reconstruction efforts should also take into account future earthquakes to avoid a high human toll, the scientists said.

Their worries about the next big one stem from the lack of aftershocks south of the Dec 26 earthquake's epicentre, 150km off the north-western coast of Sumatra. On that fateful day, aftershocks occurred north of the main jolt along the Sunda Trench, tracing a path up through the Indian Nicobar and Andaman Islands towards Myanmar.

But the earth south of it did not move, suggesting that 'there has been no relief of the stress there', said Dr Jonathan Husch, a geological and marine science professor specialising in earthquake and volcano research at Rider University in New Jersey. This would make a large earthquake 'possible further to the south and east', he added.

Studies show such giant earthquakes recur every 200 years or so, which makes the southern parts of the Sumatran fault 'dangerous over the next few decades', said Professor Kerry Sieh from the California Institute of Technology. Prof Sieh, who has studied the Sumatran fault for over a decade, had warned just a week before the Dec 26 quake that a giant earthquake was overdue around Sumatra. He gave the warning at a seminar in San Francisco.

The last major earthquake to rock the area occurred more than 170 years ago in 1833 off central Sumatra, an 8.7-magnitude shock that sent smaller tsunamis up to 1.5m high onto the coasts of many of the same countries affected by the Dec 26 quake, according to Geoscience Australia's website. The 1977 Sumbawa and 1997 Java earthquakes sent tsunamis between 4m to 6m high crashing on Australia's north-west coast. Sumbawa is an Indonesian island east of Java.

A computer simulation of the 1833 Sumatran earthquake showed tsunamis would have hit Australian shores from Perth to Broome in West Australia. There was little damage and no lives were lost in the sparsely populated areas.

Work on the tsunami warning system in the Indian Ocean, spearheaded by the United Nations, is expected to be completed by June next year. The deep-ocean buoys will detect the passage of the giant waves in the open ocean, and sound the alarm for coastal populations to evacuate.

Tsunami warnings, which can range from minutes to hours, should go hand-in-hand with education, said Dr Joan Gomberg, a seismologist with the US Geological Survey. 'A huge number of the deaths could have been prevented if people had been educated to go to high ground when they felt an earthquake and systems were in place to get information distributed about the likelihood of a tsunami hitting,' she told The Sunday Times.

If reconstruction must take place in active earthquake zones, steps should be taken to 'ensure that buildings are built to withstand the levels of shaking they are likely to encounter', said Dr Eugene Schweig, coordinator of the Earthquake Hazards Programme Office of the US Geological Survey.

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