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Creation Date: Mon, 28 Feb 2011 GMT

Tough building codes couldn't save Christchurch

Despite Christchurch having one of the strictest building codes in the world, seismologists say they still could not save the city from devastation.

In recent decades New Zealand engineers have followed the same guidelines used in other quake-vulnerable regions such as California and Japan.

And despite the rigorous building standards, the problem on this occasion is that the underground fault line was not really known about until last September.

But Geoscience Australia seismologist Dr Trevor Allen says a lot of buildings in the Christchurch CBD were built before stringent earthquake building codes were introduced.

"[There are] a lot of un-reinforced masonry buildings which are very vulnerable to earthquake ground shaking," he said.

"Now substantial efforts have been made to make those buildings more resilient, but unfortunately following on from September's earthquakes many of the structural features of those buildings were compromised."

New Zealand's construction code is one of the most comprehensive and stringent in the world, a point former prime minister Helen Clark made to the BBC.

"In Wellington, sitting in my prime ministerial office or in the official residence during the year, I would feel the building shake and they were adapted for that," she said.

"But clearly the level of building resilience in Christchurch was not up to, in every case, dealing with this shallow and quite severe shock.

"I guess it will be back to the textbooks now to see what further work needs to be done to really ramp up New Zealand's resilience. I don't think we'll hear anybody complaining about strict building codes ever again."

'Unusual' event

While the Shaky Isles are known for their seismic activity, Geoscience and Isotope Research Agency seismologist John Ristau says what happened in Christchurch is different.

"What was a bit unusual was just to have the magnitude-7 earthquake in the first place in that area around New Zealand, because the Canterbury region is not known to be particularly seismically active," he said.

"It was buried under deposits that were 20,000 years old and it hadn't been mapped before. So the fault was always there, we just didn't know it existed."

NZ Master Builders Federation spokesman Warwick Quinn says the trouble is it is not always possible or practical to guard against the unknown.

"It's not as if it was something that was missed, it was just unknown," he said.

"Construction may not have reflected what would have otherwise have been the case had they known there were faults through it.

"Whether or not that would have made a difference we'll never know."

Building code overhaul

A US earthquake recovery specialist believes the destruction could bring about a dramatic shift in Christchurch's building codes.

Lon Determan, whose company Miyamoto Associates has helped earthquake recovery efforts worldwide, has sent a team to Christchurch.

He says authorities may order buildings to be substantially upgraded when rebuilt.

"You always have to balance cultural heritage with life safety," he said.

"You have to balance that with the costs of a full upgrade and providing some degree of life safety and reduced hazards.

"In other cases it may be signs of inadequate quality control during construction.

"Generally you have code cycles that address the lessons learned from each subsequent earthquake.

"How you get those addressed is through updating codes and potentially activating some certain city ordinances to require upgrades on buildings such as historical heritage buildings."

Emily Bourke and Michael Edwards, 'ABC News', Wednesday 23 February.