THE impact of any tsunami, triggered by quakes in the region, on Singapore would be minimal, according to a new two-year study.

Computer simulations used in the study found that it would take an earthquake, in Indonesian or Philippine waters, measuring about 9.0 on the Richter scale to generate a tsunami powerful enough to reach Singapore.

Even then, it would take 10 hours before the first waves hit the island.

By that time, the waves would be no more than 0.7m above the average sea level, reaching no more than 50m inland and at speeds slower than that of normal tides.

The National Environment Agency (NEA) commissioned the National University of Singapore (NUS) and Nanyang Technological University (NTU) to conduct the study in 2006.

The aim of the study was to discover the effects of tidal waves, caused by underwater earth movements, on Singapore.

This was in response to the Indian Ocean tsunami on Dec 26 four years ago, which killed more than 225,000 people. The epicentre of the earthquake that caused the tsunami was in the sea near Indonesia, known as the Sunda Arc.

This area, together with another area called the Manila Trench near the Philippines, was identified as a hot spot for underwater movement which could pose a tsunami threat to Singapore.

Earthquakes in the region usually measure 6.0 to 8.0 on the Richter scale, apart from the massive quake in 2004. There was also one measuring 8.7 in 2005 and only two measuring 8.5 to 9.0 in the 19th century.

The Richter scale goes up to 10 points. Earthquakes measuring about 8.0 occur once a year and can cause serious damage in areas several hundred kilometres from the epicentre.

Earthquakes at 9.0 on the Richter scale have devastating effects several thousand kilometres away and occur once in 20 years.

An earthquake measuring 10 on the Richter scale has never been recorded.

Earlier this month, NTU researchers said they had detected signs of an earthquake off the Indonesian island of Sumatra but could not predict when or where it would strike.

It is, however, unlikely to be as large as the 2004 one.

The shallow waters and land masses around Singapore protect the island from the effects of any tsunami, said Mr Foong Chee Leong, the director-general of NEA's meteorological services.

Even during the 2004 earthquake, there was no record of a rise in Singapore's sea level, he said.

The speed at which any tsunami wave would hit Singapore's shores - at half a metre per second - is slower than the speed of a normal tide, which is 1m to 2m per second, said one of the NUS researchers, Dr Pavel Tkalich.

The study costs $1.3 million and made use of a modified program used in Japanese tsunami warning systems, which are considered among the best in the world.

Six Singapore beaches were identified as potential risk areas: West Coast Park, Labrador Park, Sentosa, the Southern Islands, East Coast Park and Pasir Ris Park.

But these areas pose a limited threat because the nearest residential area from the coastline is about 80m inland and any built- up area was constructed at least 1.25m above the highest tide level of about 1.5m above the average sea level here, said Mr Foong.

Dean of NTU's college of engineering, Professor Pan Tso-Chien, said the only worry would be people on the beach.

'Those in the sea would feel like they are riding a wave, bobbing up and down,' he said.

'The waves, by the time they hit the beach would be less than 1m high, at very low speeds, and (they) wouldn't be able to cause any destruction.'

wycin@sph.com.sg