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  Channel NewsAsia 26 Dec 05
Bigger tsunami possible, Singapore would feel ground shake: expert
By Asha Popatlal, Channel NewsAsia

Today Online 27 Dec 05
Not 100% quake-proof: Big tectonic shift in Sumatra may harm S'pore, says expert
Derrick A Paulo derrick@newstoday.com.sg

READERS this past week have been left wondering if they will ever see towering waves smashing onto land here in Singapore.

They might be better off focusing on the waves they cannot see.

Powerful seismic vibrations caused by a massive earthquake in nearby Sumatra are more likely to reach Singapore and will pose a greater threat, according to Professor James Rice (picture), a Harvard don who will be coming here next month.

Neither a tsunami nor a temblor is known to have harmed Singapore, which sits near an area of high earthquake activity, but slight tremors from previous earthquakes have been felt here.

What if a big one hits?

Prof Rice's research shows that the biggest threat to Singapore is an epicentre off central Sumatra, about 500km away, where the Indian Ocean is closest to the Republic. Although such a distance would typically mean "benign shaking", there have been exceptions, said the engineering sciences and geophysics expert.

In 1985, an earthquake greatly damaged Mexico City and killed thousands of people. Its epicentre was 300 km away. "That was a magnitude 8.5 quake. A magnitude 9.1 quake would have meant four times the area affected in Mexico," said Prof Rice, adding that if such a quake occurred in Sumatra, it would "to some extent be felt in Singapore".

In 1833, a "monster earthquake" estimated to be up to 9.0 on the Richter scale occurred off central Sumatra, about 500km away from Singapore.

Said Prof Rice, a board member of the Southern California Earthquake Center: "It would be worthwhile for scientists in Singapore to say, 'Let's suppose a tectonic slip comparable to last December's--magnitude 9.0, 900km away--were to occur in Central Sumatra.' So, where would you have strong shaking? Where would that shaking be magnified?" A harder task would be of gauging the chances of such an earthquake striking again, and if so, when, given that seismic activity in the region has increased recently.

All that research can say is that earthquakes do repeat themselves, said Prof Rice. "I could say an earthquake repeats every 240 years on average. But there is enormous fluctuation in that 'average time'. It could be between 100 and 400 years," he told Today.

But with many parts of Singapore built on reclaimed land and marine clay, studies of the earthquake threat are important. Much of Mexico City also sits on soft soil--clay with layers of sediment--which made it vulnerable to the 1985 quake.

Careful soil engineering can help mitigate the effects, and Prof Rice is eager to learn how prepared Singapore is when he arrives here to give a lecture at the National University of Singapore.

However, one year after the Indian Ocean tsunami, why does a repeat of that disaster not rank high as a threat to Singapore?

"Because Sumatra is and has always been a natural buffer. And no Sumatran earthquake provides a tsunami threat," he said.

He is also doubtful the epicentre is moving north to the Andaman and Nicobar islands, as argued by Thai seismologist Dr Smith Dharmasaroja. "A case can be made that it is also moving south," said Prof Rice.

Channel NewsAsia 26 Dec 05
Bigger tsunami possible, Singapore would feel ground shake: expert
By Asha Popatlal, Channel NewsAsia

SINGAPORE : One year after the Indian Ocean tsunami, people are asking if it can happen again and if so, when and where. Geological expert Professor James Rice of Harvard told Channel NewsAsia another major earthquake and an even bigger tsunami is a very real possibility in Sumatran region.

But as far as Singapore is concerned, its impact is likely to be confined to feeling some ground shaking in the wake of the quake. 'Tsunami' was a word few knew before last December; but in the wake of its devastating impact, many now know what it can do. The question is, can something like this happen again?

The simple answer is 'yes'; as for when, that is not so easy to answer

Said Professor Rice, "The average repeat time of such earthquakes is 200 to 300 years, but that's an average and it varies greatly. It could be anywhere from tomorrow to 400 years from now. It's very unlikely now that anyone living now in that area which experienced the big tsunami will experience another big tsunami in their lifetime.

He added, "But there is going to be an earthquake that will produce a massive tsunami in that part of Sumatra, with considerable ground-shaking that will affect Singapore and South Malaysia more than the one in December of last year."

While it may be impossible to escape from Mother Nature's wrath, there are lessons to be learnt.

One is education, so that people know what to do in the event of a tsunami.

Professor Rice said, "One thing to start with is education. Everyone should know when they live along a margin susceptible to tsunami, everyone should know when the water retreats you don't follow it out of curiosity, you get to higher ground as fast as you can. There ought to be regular posted signs along the beaches."

The second lesson is advance warning systems, which can give up to about a minute's warning on public broadcast systems before a tsunami arrives.

And the third is looking at the design of the buildings that survived and ensuring such buildings as shopping malls exist, and that people know to get to them.

However, Professor Rice concedes some coastal areas, especially in remote parts of Indonesia, are just too vulnerable. For the long term, the governments of these areas may need to think of relocating such communities elsewhere. - CNA /ct
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