New Zealand Embassy Beijing, China

Christchurch Earthquake

New Zealand Minister for Building and Construction, Hon Maurice Williamson, visited China 23-29 October. During his visit he discussed the Christchurch earthquake in September and New Zealand's earthquake proofing and management systems with Chinese counterpart Minister Jiang Weixin of the Ministry of Housing, Urban-Rural Development.

An interesting report on the Christchurch earthquake in Chinese newspaper Southern Weekend (Nanfang Zhoumo) can be found here (below in translation).

Big earthquake in New Zealand: “Zero Deaths” is the result of how many years’ efforts?
How do 4 million New Zealanders view the “miracle” in the eyes of 1.3 billion Chinese?

By Peng Liguo, Southern Weekend (Nanfang Zhoumo), 16 Sep

Is this just a matter of luck?

“Staying in a one-or-two-floor residential building is much safer than running out.”

It was 4:36 in the early morning in New Zealand on 4 Sept. Sun Siwei, a freshman of the Engineering College of the University of Canterbury, was preparing for examinations overnight. Without any warning signs, the 7.1 magnitude seismic wave travelled from the small town of Darfield and struck the city of Christchurch, the second largest New Zealand city and provincial capital of Canterbury where he lives.

At seven o’clock in the morning, he decided to go out and look around. His neighbour, 80-something year old Mr Baker was taking care of his garden. In a nearby park, housewives were joking about how many vases were broken. He was confused: did an earthquake happen at all?

The earthquake did happen. This is the most destructive earthquake to hit New Zealand in 70 years. For Canterbury, there has hardly been one at all in the past hundred years.

But it was as if the earthquake didn’t happen. At midday, Prime Minister John Key declared to the world, “it’s a miracle that nobody was killed.” With only two serious injuries, the impact was even less serious than a traffic accident.

The “less serious than a traffic accident” miracle shocked the world, which had not yet recovered from the painful memories of Wenchuan, Haiti Port-au-Prince, and Chile amongst others. New Zealand made the top headline of global newspapers the next day.

While experts from all countries are trying hard to deduce the reason behind the zero casualties, some New Zealanders think it was just a matter of good luck. “I’m sorry but we really don’t have any ‘secret weapon’, much as we would like to. All we had was good luck,” Sara from New Zealand GeoNet website calmly told Southern Weekend.

The good luck she mentioned was the timing of the earthquake, which happened in the early morning when everyone was asleep. “If it happened during the day time when everyone was outdoors, there would probably have been more casualties, particularly due to masonry falling onto the sidewalk.” Mrs Smith of Darfield also said that, according to normal routines, some people would have been in the clubs and bars if the earthquake had hit two hours earlier. If it had occurred two hours later, then some people would have been outdoors. “In that case, it would have been a different story.” This was an earthquake which hit without warning. “The Canterbury plain is covered by gravel and thus we don’t see any trace of fault activity”, making it difficult to predict this earthquake,” said an expert on a New Zealand geological website.

Although most New Zealanders are given good emergency preparedness education, this earthquake did not allow them time for practice. From the perspective of Chinese-New Zealand earthquake engineer Ma Junming, the timing meant people were sleeping and did not have time to get out of their rooms at all, “Staying in a one-or-two-floor residential building is much safer than running out.”

“A zero death toll is a miracle. But we regard it as a well-prepared miracle,” said Ma Junming.

The cabin floating like lotus leaf

“Earthquakes don’t kill people. Bad buildings do.” “It is true that the outcome in New Zealand was no surprise.” As an earthquake engineer who does not have any religious beliefs, Chairman to Risk Solutions International (RSI) Peter Yanev explained the “miracle” from his perspective: “If my memory serves correctly, most New Zealanders live in light wooden structural houses that can withstand intensive earthquakes, just as we do here in California.” Will you be safe in your own little wooden house when an earthquake strikes? Undoubtedly, this conclusion almost embarrasses all scientific emergency measures.

Ms. Alexandra’s house stayed safe and sound in Christchurch’s CBD, 41 kilometres away from the epicentre; Sun Siwei’s house stayed safe and sound 25 kilometres from the epicentre; and Mr and Mrs Smith’s house also stayed safe and sound in Darfield, 3 kilometres from the epicentre. Those houses, like almost all residential buildings in Christchurch, are “light wooden structures”, which stand only one-or-two-floors high with masonry materials used for outer wall decoration or the rooftop chimney only. Such wooden houses do not fall down during earthquakes, even if the outer walls collapse. With a population density equivalent to only 1/9 of that in China, New Zealand has enough space for its citizens to reside in independent-standing cabins: “88% of civilian buildings in New Zealand are of wooden structures,” said Ma Junming.

Besides the wooden framework, there is another secret beneath the houses, called “base-isolating bearings” by earthquake engineers. Ms. Ivy, a dress designer living in Christchurch, said her house was not directly tied to the foundation, but had a huge isolator placed in between. When the earthquake hit, she felt as though her house was on a lotus leaf. “No matter how hard the water under it was boiling, the lotus leaf only moved slightly.” None of those cabins “floating” on the seismic wave had their outer walls fall or chimneys collapse completely.

Professor Andy Buchanan with the Department of Civil and Natural Resources Engineering at the University of Canterbury told Southern Weekend that these structurally light wooden houses were carefully designed to comply with the earthquake resistance standards set by earthquake engineers. “No civilian buildings collapsed, so that people who slept inside did not die.” “Earthquakes don’t kill people, but bad buildings do.” This faithful motto of New Zealand’s circle of earthquake engineering was fully exemplified in the earthquake.

How big is the earthquake problem?

“The earthquake problem in New Zealand is only a problem of scientific interest, not a problem to be watched out for.”

It has, however, taken New Zealanders more than one hundred years to travel along the tough road to reach the “floating cabins”. Earthquakes frequently hit the country located on the junction of the Pacific Plate and the Australian Plate. More than 15,000 earthquakes are located and recorded every year in New Zealand by GeoNet scientists. Since 1960, the country has experienced twenty-one earthquakes measuring above 7.0-magnitude. Each of them has been a reminder of the big one.

The earliest reminder was the Martinborough earthquake in 1848. Newly-settled European migrants suffered disastrous losses in the 7.5-magnitude earthquake, the earliest one on record, with almost all masonry collapsing. Many people built wooden houses during the reconstruction period. These wooden buildings suffered the least damage while newly-built masonry suffered a repeat tragedy when a 8.2-magnitude earthquake, the biggest ever in New Zealand, hit Wairarapa in 1855. The residents of a young Wellington city learned from the two reminders that they had to obey the laws of this island if they wanted to settle down. Wooden structural houses began to dominate for the first time. Therefore, Professor Buchanan from University of Canterbury viewed 1855 as the turning point when New Zealand started to take earthquake-resistant construction seriously.

Merely twenty-five or thirty years later, people’s awareness of construction safety slipped. Encouraged by the government’s Defence Act, masonry that could stave off fire debuted again. Fortunately no major earthquake was experienced in the first thirty years of the 20th century, and thus the comments in the New Zealand Official Yearbook from 1913 to 1926: “the earthquake problem in New Zealand is only a problem of scientific interest, not a problem to be watched out for.” Forgetting the past led to immediate punishment. In 1931, a 7.8-magnitude earthquake ravaged the whole Hawke's Bay area including Napier, again knocking down massive pieces of masonry. This devastating quake caused at least 256 deaths, most of which were caused by collapsing buildings.

After that, a construction committee carefully investigated the causes behind the housing collapses and introduced a guide to building, which was considered to be the embryonic form of New Zealand’s Building Code. The Building Code, officially legislated in 1935, requires even masonry to be firmly reinforced.

Amendments were made to the Act four times from 1965 to 1992, but no regulation was made regarding construction materials or structure of residential houses in the law even under the new Building Act 2004. “Unless classified as historical heritage sites, residential buildings do not face much mandatory regulations of law,” said Ma Junming. Nowadays light wooden structures are chosen by New Zealanders by their own free will.

Controversy over “National Building Specifications”

“The reason is very simple: it can save the people’s lives.”

In fact, New Zealand is not a medieval country filled with two-story wooden houses. Skyscrapers stand row upon row as well as a lot of old, heavy masonry which meet national regulations and building standards. In 2004, the Department of Building and Housing adopted the Building Act 2004, which set the most-detailed-ever standards for defining the earthquake-prone buildings. This Act authorises local government to assess every building higher than two floors or comprised of more than three residential units. Buildings cannot be occupied anymore without reinforced measures or demolition once classified as unable to withstand moderate earthquakes.

Actually, many authorised local authorities went further beyond this Act. “Existing buildings must be strengthened to 34% of the capacity of a comparable new building, yet the percentage was raised to 50% by many local governments” said Ma Junming.

Although praised by earthquake engineer experts as “a big step forward”, this Act aroused controversy since the very beginning of its implementation. As it applies to new masonry and reinforced concrete buildings and also old buildings classified as “historical heritage” before 1976, almost all the buildings in New Zealand had to be reconstructed or reinforced, except for small wooden residential buildings, according to the Act. Such a huge project could not be funded by government subsidies alone. Strengthening or rebuilding was no small cost to property owners.

But laws are made to be followed. The assessment and strengthening work moved forward despite difficulties. Consultant teams composed of earthquake engineering experts from the University of Auckland and the University of Canterbury rushed worked on old or newer buildings. All the buildings, no matter owned by the poor or the rich, no matter whether they were located in the urban or suburban, were upgraded to meet the “National Building Specifications (NBS)”. The 4 September earthquake, the most devastating earthquake in 70 years, has been the best test for the Act and these efforts.

A team of experts including Professor Buchanan has started assessment of damage to buildings since the earthquake. They discovered that most of the collapsed buildings were built before the 1970s and not yet been reinforced. “Many old buildings reinforced to 2/3 of the NBS were not ruined. And new buildings combined with reinforced concrete and steel frame did not really suffer any damaged at all,” Charles Clifton, expert on reinforced concrete, told Southern Weekend.

Christchurch Mayor Bob Parker announced a change in building policy on 10 Sept, requiring the 960 existing earthquake-prone buildings to undergo strengthening to 67 percent of NBS levels, rather than 33 percent as was previously the requirement. He suggested that this higher standard be applied immediately.

The target was the same as set in Gisborne after its 6.8-Magnitude earthquake in 2007. The Mayor of Gisborne, Meng Foon, a Chinese descendant, told Southern Weekly. “This earthquake proved once again that the new building code is reliable. The reason is very simple: it can save the people’s lives.”

“Professional without corruption”

The zero death toll in the Christchurch earthquake is “an ode to professional engineers”.

The Christchurch Cathedral, a landmark of Christchurch city, is more than a hundred years old and was strengthened by professional engineers. After the earthquake struck, all the Christchurch people wanted to know how it had stood up to the shock. The old cathedral made it.

This miracle would not have happened without professional engineers observing the Building Act. For Buchanan, the zero death toll in Christchurch earthquake was “an ode to professional engineers”. Peter Yanev praised highly his Kiwi colleagues: “New Zealand has the most brilliant earthquake engineering experts in the world. Their performance is particularly remarkable considering the general population. Many top earthquake engineers in California have migrated from New Zealand in the past fifty years. Thanks to their help, California has become safer.”

New Zealand earthquake engineers well deserve such praise. “New Zealand is the first country that designed a reinforced concrete building so that it would not fall in an earthquake. This seismic scheme called ‘Capacity Design’ has been used worldwide. New Zealand is also the first country that developed and applied a seismic isolation system. This technology can put a building on special base isolating bearings to avoid structural destruction,” said Andrew Charleson, an expert on buildings from the University of Victoria, Wellington.

There are far more facts to list. Well-known inventions in the global earthquake engineering community including “ductility design” and “lead-rubber base-isolating bearing” are all invented by New Zealand earthquake engineers. The latest update is that the “Displacement-Based Seismic Design” invented by Professor Nigel Priestley with the New Zealand Society for Earthquake Engineering may become the big news in earthquake engineer design. This design has been put into use in Europe and New Zealand.

All of these inventions ensured that historical treasures such as the Christchurch Cathedral can survive earthquakes. What’s more, they are not only applied in Kiwis’ homes, many of them have also taken hold worldwide as national standards.

However, Buchanan thinks having skilful and professional engineers in themselves is not enough. New Zealand’s good luck is largely attributed to a huge number of honest construction companies and construction monitoring supervisors working beside those engineers. “Of course the building code is important. But what’s more important, is a high degree of professionalism without corruption,” said Buchanan. This seems to be another “secret weapon” of New Zealand.

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