Christchurch needs to prepare for the big one

Christchurch needs to prepare buildings for the ‘big one’

As Canterbury recovers from the 4 September earthquake and attention begins to focus on rebuilding the city centre, two leading academics from the University of Canterbury are warning that this is not a time for complacency in setting building codes and earthquake research.

Professor Andy Buchanan and Associate Professor Greg MacRae, both from the University’s College of Engineering, said the recent 7.1 quake was a mere warning bell and nothing like the predicted ‘big one’.”

“Our concern is that people are saying that the current standards are more than enough because everything survived so well, but there are others of us saying let’s be very careful here because there is still a larger earthquake predicted,” said Professor Buchanan.

“From a structural point of view the surprise is the low level of damage in Christchurch and the reason is that although it was a large magnitude earthquake, the level of ground shaking affecting most of the buildings we have in Christchurch was only about 60% of what we design for, and it was definitely not as much as it will be when we get the big one.”

Both Professor Buchanan and Professor MacRae cited Chile as a perfect example for Christchurch to consider. It had an earthquake in 1985 and, because its buildings all survived, it did nothing to strengthen its building codes. In 2010 it had a much more severe earthquake with very serious damage and loss of life.

“Because this is the first major earthquake in an urban area since Napier in 1931, there are many lessons we can learn for the future,” said Professor Buchanan.

“Basically, the unreinforced masonry buildings in Christchurch that had been re-strengthened have done very well and many of the ones that have not been strengthened have had a lot of damage.

“Concrete buildings fared better, but that was more to do with the size of the quake. We know that this will not be the case when a bigger quake strikes.”

Professor Buchanan said that research work carried out at the University in earthquake-proofing buildings was a key factor in restricting damage in the city to a predicted $4 billion.

“Money spent on research has saved hundreds of millions of dollars, but we need to continue this investment if we are going to future-proof buildings against potentially bigger earthquakes.

“We are fortunate in that the university has close working relationships with industry and with research organisations such as GNS Science, BRANZ, the Foundation for Research, Science and Technology as well as the Earthquake Commission.”

Professor Buchanan said that the key focus at present was researching how to economically protect buildings from the biggest of quakes.

“If this earthquake was bigger there would have been some concrete buildings that would have had to be demolished. What we are trying to do is come up with ways to design and protect buildings so that in the biggest of earthquakes they do not have to be demolished.

“The first question that needs to be asked is: ‘Are the specifications we have at present good enough?’ And the answer is no. The second question is: ‘What do we need to do?’ That’s simple. Continue to invest in research to make the protection of buildings more affordable.”

ENDS