Filed under 香港政治
It appears that there’s nothing about the Manila Trench released to the public by the Royal Observatory Hong Kong.
Is HK safe from tsunamis? Experts say no
Associated Press and Chris Ip
SCMP Apr 20, 2011
A computerised simulation of seismic dangers by a US professor and his team found that a magnitude 9 quake along an ocean trench in the South China Sea would trigger tsunami waves up to eight metres high that could hit Hong Kong and nearby cities.
Contrary to the traditional wisdom that Hong Kong is not at risk from major earthquakes and tsunami because of its location, the study by David Yuen, a University of Minnesota professor who has modelled seismic probabilities in Asia, concluded that a risk did exist and the consequences could be catastrophic.
“We have to assume they’ll be hit," said Yuen. “Maybe not in the next 10 years, but in 50 or 100 years."
The computerised stimulation by Yuen and his students shows that if a magnitude 9 earthquake struck the Manila Trench – an underwater trench in the South China Sea – it would generate huge waves racing across the sea to slam Taiwan’s southern shores 15 minutes later. The tsunami would reach China’s southeastern coast in around two hours and strike Hong Kong.
In the worst-case scenario, the tsunami waves hitting Guangdong, Hong Kong and Taiwan would be five to eight metres high.
Yuen warned that, with a growing number of nuclear power plants being built in the region, such a wave could have catastrophic consequences similar to those seen in Fukushima, Japan.
A Hong Kong scientist yesterday said that while such an event was only likely to occur “once-in-a-millennium", the risk was real.
“This is something that the Hong Kong government and the Observatory need to take seriously," said Dr Zong Yongqiang, an associate professor of earth sciences at the University of Hong Kong.
“People have very short memories. Most people are only interested in recent earthquakes. If you [only] look at the records over the past 100 years, there are small earthquakes here and there along the south coast of China. That gives people a false impression that Hong Kong is very safe," said Zong.
But he said to correctly assess the probability of an earthquake on the scale of the one last month in Japan, researchers would need to dig up centuries of data.
Paul Tapponnier, a tectonics expert at the Earth Observatory of Singapore, agreed.
“You [in Hong Kong] are not far away from any place that could affect you in terms of tsunamis," he told the South China Morning Post (SEHK: 0583, announcements, news) .
He said the fact that there had been so little study into the probability of earthquakes and tsunamis in the South China Sea was a serious concern.
“We don’t know anything yet. We don’t yet have a catalogue of tsunami deposits on China’s coasts."
Tsunami deposits are the debris left on the shores of areas hit by tsunamis in the distant past.
Adam Switzer, the principal investigator of the tectonics group at the Earth Observatory of Singapore, is researching tsunami deposits along the coast of China.
Asia, the world’s most seismically unstable region, is undergoing a nuclear renaissance as it struggles to harness enough power for its huge populations and booming economies.
But the mainland, Taiwan and several other places frantically building coastal facilities have made little use of new data to determine whether these areas are safe.
Li Zhong-cheng of the National Energy Centre in Beijing told the state media after last month’s disaster in Japan that China’s coastal areas were protected by a wide, shallow continental shelf that was not conducive to the formation of big tsunamis.
Other scientists say there is not enough research to make such a declaration.
Some historical records, though inconsistent, indicate that a 10-metre tsunami wave in 1782 from the South China Sea killed as many as 40,000 people in southern Taiwan.
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