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Japanese Tsunami 2011

On March 11, 2011, a devastating 9.0 earthquake and tsunami struck Japan, claiming the lives of more than 15,000 people. It was the most powerful known earthquake ever to have hit Japan, and one of the five most powerful earthquakes in the world. In the aftermath, a state of emergency was declared following the failure of the cooling system at the Fukushima Daiichi Nuclear Power Plant, resulting in the evacuation of nearby residents. Radiation levels inside the plant were up to 1,000 times normal levels, and those outside the plant were up to eight times normal levels. 

Could it happen here?

PUBLISHED : Sunday, 11 March, 2012, 12:00am
UPDATED : Sunday, 11 March, 2012, 12:00am

At a recent luncheon at the Foreign Correspondents' Club in Central, business executives, lawyers and journalists mingled while feasting on sole fillet and beef goulash. It was the sort of event at which people do not take themselves - or anything - too seriously. By the time coffee was served, however, the atmosphere had turned gloomy; guest speaker Ian McFeat-Smith had taken to the rostrum to expound on the vulnerability of Hong Kong to a major earthquake.

'I believe we are a big, fat sitting duck,' he told his audience.

The Scottish engineering geologist has recently released a novel that tells the story of a young geologist correctly predicting a big earthquake striking Hong Kong. McFeat-Smith, who is involved in assessing underground projects in Hong Kong and Southeast Asia, believes the real risk of a major earthquake and tsunami hitting the city is far greater than commonly believed and since the city has taken no measures to guard against such a disaster, he considers the risk 'intolerable'.

McFeat-Smith's pessimism resonates with concerns about Hong Kong's seismic vulnerability that emerged locally after a magnitude 9 quake and tsunami ravaged northeast Japan a year ago today. The Tohoku disasters, which began on March 11, killed 15,800 people, damaged or wrecked 125,000 buildings and sparked a nuclear crisis that is ongoing. As soon as the public psyche had absorbed the enormity of the disaster, questions were raised over how at risk Hong Kong was to similar misfortune. Internet forums bristled with concerned posts. One commenter on the popular Golden Forum ventured that Hong Kong would see 'the biggest domino effect in the world' if it were struck by a major quake. As the Fukushima nuclear crisis unfolded, concerns mounted over the Daya Bay nuclear power plant, a mere 20 kilometres from parts of Hong Kong.

Public concern, according to McFeat-Smith, was warranted: 'Risk is not just about likelihood. You must consider the consequences. As Hong Kong is growing, the complexity of our earthquake risk increases,' he said. 'I believe in extreme circumstances, Hong Kong might fail to exist should we experience a large earthquake.'

Earthquake specialists would not go that far, but they do acknowledge that serious damage could be done in a densely populated city with 60,000 high-rises. What's more, the surprising magnitude of the Japan mega-quake has led some scientists at home and abroad to conclude that, if a big quake were to strike the Philippines, there would be a high risk of Hong Kong being hit by a tsunami capable of wiping out houses in Stanley and flooding Tsim Sha Tsui.

'Hong Kong is very prone to tsunamis but it doesn't have any safety measures,' says Wu Tso-ren, a tsunami expert and assistant professor at the National Central University in Taoyuan, Taiwan. 'It should do something as soon as possible to protect itself.'

According to the Hong Kong Observatory, 90 per cent of all earthquakes occur along the boundaries of crustal plates. In other words, 'the chance of strong earthquakes occurring in Hong Kong is very low', given the city is 600 kilometres from the nearest plate boundary.

Since recording began, in the early 1900s, a total of 168 earthquakes have been felt in Hong Kong. The latest, the epicentre of which was in Heyuan, Guangdong, occurred just a few weeks ago. The city's biggest recorded tremor, in 1918, was the result of a magnitude 7.3 quake hitting Shantou, 300 kilometres away. Then, a handful of local buildings were affected: a house on The Peak was vacated, the Hong Kong Club in Central reported cracks on the walls and St Stephen's Girls' College on Caine Road was seriously damaged. Yet there were no casualties here, as has been the case with all the other seismic events that have been felt in the city.

This, however, does not mean Hong Kong is immune from devastating earthquakes, says Chau Kam-tim, chair professor of geotechnical engineering at Polytechnic University and scientific adviser to the Observatory. 'We get the impression that Hong Kong doesn't have any earthquake risk because we've never been hit before,' Chau says. 'But having a low to moderate seismic risk is not the same as having no possibility of major earthquakes. If you analyse in detail, you'll find that most of the major earthquakes over the past few decades occurred in places previously thought to be low risk.'

The biggest concern, according to Chau, lies in a seismic fault zone near the Dangan Islands, about 35 kilometres south of Hong Kong. It is regarded by some scientists as being the most likely source of a quake big enough to cripple Hong Kong. The Civil Engineering and Development Department says the seismic activity around Dangan is 'a significant factor as far as earthquake hazard is concerned'.

The Dangan Islands sit between two past earthquake epicentres: Shantou in the northeast and, in the southwest, Qiongshan, which was devastated by a magnitude 7.5 quake in 1605. Chau says the two sites mark the ends of the massive Binhai fracture zone. Some geologists believe that between these two ends, there is a missing earthquake zone, in which major quakes could occur, and that the Dangan Islands are within this zone.

The Dangan fault zone is considered capable of generating earthquakes of up to magnitude 7.5. Should one be unleashed, Hong Kong would be 'in big trouble', says Chau.

'For an area so close to Hong Kong to be struck by a big earthquake, the impact on the city would be massive. Buildings might collapse or be damaged beyond repair, leaving many people without shelter. Even if there were not a great number of fatalities, the economic loss would still be inestimable,' he says. 'And don't forget earthquakes in the northern South China Sea are mostly shallow earthquakes, which are more damaging than deep ones.'

It is not as if shallow earthquakes have not occurred near Dangan before. In 1874, a magnitude 5.75 quake shook the sea near the islands. According to the now-defunct Daily Press, some people in Hong Kong were injured, two houses collapsed, boulders fell from slopes and Victoria Harbour was 'rough and buoyant'. In September 2006, Dangan was hit again, by a magnitude 3.5 quake, which was widely felt in Hong Kong, Macau and southern China. Residents in Shek O and Cheung Chau reportedly ran into the streets; local radio stations were bombarded with phone calls and e-mails.

Could the big one strike Dangan in the foreseeable future?

'There are two schools of thought,' Chau says. 'One says both ends of the Binhai fracture zone have had their big quake in recent times, so things have calmed down and will remain stable. The other school argues that since the middle section has never been hit, it is the most dangerous part and would unleash the most energy when a quake occurred. More seismologists support the latter theory.'

A recent study by engineering firm Arup and the University of Hong Kong gives the probability of a quake above magnitude 7 occurring within 100 kilometres of Hong Kong over the next 50 years as 1.5 per cent; for a magnitude 6, the figure jumps to between 6 and 12 per cent.

Professor Chan Lung-sang, an earth scientist with HKU, says these are low figures. Yet he warns against over-relying on them. For one thing, places of low to moderate seismicity such as Hong Kong do not offer much data from which to make predictions. Furthermore, the history of modern seismology is too brief to be entirely reliable.

'The world has a history of about 130 years of using sophisticated instruments to measure earthquakes. This is too short. To use decades of data to predict an event that might occur once every few millennia is meaningless,' says Chan, also a scientific adviser to the Observatory. 'Will Hong Kong be struck by an earthquake? Maybe, but it's very difficult to predict.'

Even in cases of an abundance of historical records, one problem is insurmountable: the caprice of Mother Nature.

'To predict earthquakes is like boiling a pot of water and trying to guess which way the water particles will go. The movement of the particles is a chaotic process,' Chan says. Which was partly why the Tohoku mega-quake surprised seismologists. A year before the event, experts in Japan had predicted there was a 99 per cent chance Miyagi prefecture would be struck by a magnitude 7.5 quake within three decades. As it turned out, the region got a magnitude 9, which was some 170 times stronger than expected.

Other recent quakes that took scientists by surprise include last month's magnitude 6.9 in the Philippines, which was caused by a previously unknown fault, and the magnitude 5.6 in Newcastle, New South Wales, in 1989, the deadliest earthquake on Australian soil. Prior to that event, Newcastle had not been thought to have a high seismic risk.

'The problem is, the existing method for earthquake predictions is inadequate because it is very much based on past events,' Chau says. 'The Tohoku earthquake woke us up [to the fact] that nature is much more complicated than we thought.'

'After the Japan earthquake, a lot of geologists had to rethink everything,' says David Yuen, a tsunami expert and geology professor at the University of Minnesota, in the United States. 'The whole thing taught us a lesson.'

It was a lesson that prompted Yuen, a Shanghai native raised in Hong Kong, to reassess the seismic dangers in the South China Sea. Shortly after the Tohoku disaster, he and his research team conducted a computerised simulation, which indicated that if a magnitude 9 quake struck the underwater Manila trench, near the Philippines, it would trigger a tsunami that would slam into Taiwan's southern shores 15 minutes later. Within two hours, waves up to eight metres high would reach Hong Kong, hitting Stanley with full force before flooding other areas. Yuen's findings differ slightly from those of a Taiwanese government-commissioned study conducted recently by Wu, but both point to a tsunami risk to Hong Kong.

'The Manila trench is very long,' Wu says. 'It's not like any major earthquake there would affect Hong Kong. 'But if a magnitude 8.35 quake occurs along a section to the northwest of Luzon - which is actually the part most likely to snap - the impact on Hong Kong would be huge. It could be hit by waves more than five metres high. For the tsunami in the open sea in Japan last March, we're talking about five to 10 metres in height.'

Hong Kong does, however, have some geographical advantages.

'The Manila trench is miles away; it would take two to three hours for a tsunami to arrive in Hong Kong. So there is time to issue a warning,' Wu says. At present, a tsunami warning would be broadcast in the same way those for cyclones are issued. To help get information out, after the Japanese quake, the Observatory launched a Twitter account: twitter.com/#!/HKOQEME.

Also, 'Hong Kong is mountainous and people can go uphill to escape,' Wu says. 'A major concern, though, is Hong Kong has a big population, so it's important to prevent pandemonium during an escape.'

Wu says the Manila trench is, in theory, long overdue a magnitude 8.5 quake. Since 1560, no magnitude 8 earthquake or above has occurred along the trench. For the past few centuries, the trench has been building up enormous amounts of energy as the Philippine Sea Plate and the Eurasian Plate continue to push against each other.

'Today the fault slip from the two plates is about 38 metres. The slip in northeast Japan was only 17 metres. The greater the slip, the more water will be heaved up to create bigger tsunamis,' Wu says.

Ander Chow, associate director of Arup, is also conducting a study on how Hong Kong would be affected by a magnitude 8.5 quake in the Manila trench. Preliminary findings show that if the city experienced a tsunami of up to two metres high, there would be significant impact on land between Stanley and Silvermine Bay, on Lantau Island. He urges the government to prepare for such an event.

'Hong Kong doesn't have any [protective] measures, which is not realistic. It's especially important to protect vulnerable infrastructure such as power stations and the MTR,' Chow says.

Says Yuen: 'We don't know when Hong Kong will be hit, but you have to be prepared before it's too late. It may be necessary to have some form of seawalls built at strategic places. The investment would not be that much when you compare this with the potential damage.'

The Observatory says it is 'always concerned with the tsunami risks facing Hong Kong, particularly those arising from earthquakes in the Manila trench'. In 2010, it opened a seismograph station in Mid-Levels to better monitor tsunamis and earthquakes worldwide. Advanced equipment was installed to estimate the arrival time and size of any tsunami reaching Hong Kong.

The Civil Engineering department, however, says there is 'no pressing need' to put in place measures against tsunamis.

'The failure of the seawall at Kamaishi [in northeast Japan] to guard against the tsunami in 2011 has also put the effectiveness of massive and costly shore protection structures in serious doubt. The government will continue to monitor the need in future,' a spokesman says.

Meanwhile, many local engineering experts - holding a range of views about Hong Kong's seismic risk - believe the city needs to make its buildings earthquake-resistant.

'Hong Kong should introduce a seismic building code. Its risk of major earthquakes is not high, but if an earthquake does happen, the consequences could be very serious,' says Kuang Jun-shang, a civil and environmental engineering professor of the Hong Kong University of Science and Technology. 'After the magnitude 5.6 earthquake in Newcastle in 1989, the [civil engineering] industry became aware that buildings without earthquake-resistant designs could wreak havoc in places of moderate seismicity.'

Hong Kong's present building code, a British colonial legacy, stipulates buildings must be able to withstand winds of up to 250 kilometres per hour. But there is no requirement on quake-resistant designs.

Shenzhen, regarded by the China Earthquake Administration to have a slightly lower seismic risk than Hong Kong, has introduced mandatory quake-related building specifications. It has also enlisted the help of lions, giraffes, tortoises and lizards. Animals are known to be good at anticipating earthquakes, so, in 2008, the Shenzhen Seismological Bureau set up observation sites at the city's Safari Park, to monitor unusual behaviour that could signal an imminent seismic event.

According to the Buildings Department, wind-resistant designs help strengthen building structures and most buildings in Hong Kong are 'basically safe in the event of earthquake'. This, it says, has been proven by a study it commissioned Arup to carry out in 2002. The three-year research zeroed in on the seismic risk to local buildings. Neither the department nor Arup would provide a copy of the findings to Post Magazine. A department spokesman says it is 'considering [the] findings carefully prior to deciding on the way forward' and no building code is being revised in relation to seismic resistance.

Nonetheless, Jack Pappin, the director of Arup who led the study, says: 'I understand the government is looking at [a seismic building code]. It is planning to develop one.'

A specialist in seismic engineering, Pappin says one of the major conclusions of the 2002 study was that 'the [seismic] risk of the existing building stock is not excessive but is not zero' and 'the risk is not high enough to warrant a mass repair system'. He deems it prudent for Hong Kong to introduce a seismic design code. 'After you've introduced a code, you start picking up from that point. Within a few decades you can improve the building stock.'

Pappin stresses that there is seismic risk everywhere and that Hong Kong is not at particularly substantial risk. Furthermore, and contrary to conventional belief, high-rises in Hong Kong have a lower seismic risk than low-rises. Any quake here is likely to deliver vigorous high-frequency shaking, to which high-rises are less vulnerable, and the energy released would be better dispersed by the taller, typhoon-resistant buildings as they flex and sway. Should a major quake strike the city, he says, 'there would be some damage' to buildings under 15 storeys tall, which constitute about 30 per cent of the local building stock, but damage beyond repair would be unlikely, thanks to their wind-resistance.

Kuang, however, believes wind and earthquake resistance are not necessarily complementary: 'Wind-resistant design is related to strength ... earthquake-resistant design is about ductility.'

Chau concurs: 'Imagine you give Arnold Schwarzenegger a big push. He wouldn't fall easily because of the strength of his body. But if you put him on a table that shakes vigorously, he would tumble over despite his strong legs. That's the difference between wind-resistant and earthquake-resistant designs,' he says.

Should a big quake happen, Kuang believes, structures at particularly high risk would be tall buildings that incorporate a ground-floor lobby or shopping centre or are fashionably constructed as 'soft storey': those with columns at ground level sacrificing the usual walls, partitions and supports. Kuang is reluctant to give specific examples but says such buildings are 'everywhere' in the city.

'If an earthquake happened, there would be relatively significant inter-storey displacement and the building could easily collapse,' he says.

Another major area of concern is the potential 'pounding effect' between neighbouring buildings - some of which are separated by less than one centimetre. In Hong Kong, they are commonly found in areas such as Wan Chai, Sheung Wan and Mong Kok. Chau says such structures are among the most vulnerable to serious structural damage in the case of earthquakes.

'When an earthquake strikes, energy will transfer from the larger building to its lighter neighbour. That will lead to great vibration of the lighter structure, which, [if it had been] standing alone, may not have suffered any damage,' Chau says.

To minimise the risk of structural damage, Chau says buildings could be retrofitted at anything from 10 to 60 per cent of the construction cost. Reference can also be drawn from Macau, which introduced a seismic building code in 1998. Under the code, new buildings have to be quake-resistant but owners of existing buildings were allowed to decide whether to retrofit their properties or not. Restrictions have been placed on existing buildings since.

It is not going to be an easy task, especially in a city where the interests of big property developers loom large, but Chau believes inaction is not an option.

'It's understandable that more attention is paid to issues like air pollution because a lack of blue sky is something visible. If you spend money on earthquake protection, taxpayers may protest,' he says. 'But Hong Kong's seismic risk is not as small as generally believed. We do need an insurance policy on this one.'

 

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