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SCMP Reporter

Areas of Sai Kung and Lantau Island would be most at risk from a tsunami close to 2 metres high if there was a repeat of the strongest earthquake  recorded in the South China Sea near the Philippines, the Observatory says.

But the weathermen said there would be a limited impact on most of Hong Kong, including heavily built-up  areas of Victoria Harbour and the south of Hong Kong Island, as they were  sheltered from direct hits by waves.

The findings were revealed after an international team of scientists found there was a 10 per cent chance of Hong Kong and Macau being hit by waves of more than 2 metres in the next 100 years, if an intense earthquake occurred on the Manila Trench, where seismic activity remains  a threat.

Cities in Taiwan were less vulnerable than those along the mainland coast, the study found.

Research by teams from the Graduate University of the Chinese Academy of Sciences in Beijing and the University of Minnesota,  using a newly developed computer model, was published in the Physics of the Earth and Planetary Interiors Journal on August 15.

The Observatory  said its own computer model had also found similar findings, but with greater detail.

Wong Wing-tak, an Observatory senior scientific officer, said some  low-lying coastal areas in the south of the mainland could be hit by waves higher than 2 metres should there be a strong earthquake in the northern part of the Manila Trench.

He said the Observatory's supercomputer had predicted that a recurrence of the strongest quake in the South China Sea, a 7.6 magnitude quake west of Luzon in 1934, could trigger a tsunami of close to 2 metres high that may hit beaches facing east in Sai Kung, and Shek Pik on Lantau Island.

'Having said that, we couldn't find any signs of local impact when we reviewed the literature about the 1934 earthquake,' Mr Wong said.

The computer modelling, which can take up to 30 hours to predict the tsunami impact of a single quake,  has been running for months and has already tested hundreds of cases. It is aimed at building up a database for a  warning system  following the Asian tsunami in 2004, in which more than 225,000 people died.

Chan Lung-sang, from the University of Hong Kong's Department of Earth Sciences, said while an earthquake in the Manila Trench could lead to a tsunami, the chances of a disastrous impact by a mega-tsunami remained low.

A  two-year study, which Mr Chan carried out with colleagues and has yet to be published, reviewed historical reports of tsunamis in southern China over the past 1,000 years and discovered the impact of such tsunamis had been exaggerated.

'The real hits that caused damage numbered just one  or two, in contrast to what was [reported] of about a dozen cases, with one  claimed to have resulted in more than 100,000 deaths or injuries,' he said.

Small tsunamis with wave heights measuring less than 30cm  have been recorded five times in Hong Kong since 1952.

The latest was on  Boxing Day last year  after a 7.1 magnitude quake occurred under the sea south of Taiwan, triggering a wave of less than 10cm  high in Hong Kong.

The earthquake caused internet connections in the region to be disrupted for weeks.

Deadly power

The 2004 tsunami devastated the shores of Indonesia, Sri Lanka, India, Thailand and other countries with waves up to 30 metres

The number of dead  or missing after the Boxing Day tsunami was: 229,866



Sai Kung and Lantau most at risk from tsunami, study finds