Expert questions lifted quake threshold

HANK SCHOUTEN
Last updated 13:34 23/01/2013

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Lifting the earthquake prone building threshold from 33 to 67 per cent of new building standard is of questionable benefit, says a British risk management expert hired by the Government.

Tony Taig, who has written a report for the Ministry of Business, Innovation and Employment, says no building that had been strengthened to the 33 per cent threshold or better collapsed and killed anyone in the Canterbury earthquake on February 22, 2011. 

''Buildings strengthened over and above the current threshold sustained less damage than those strengthened just to the threshold, but many such buildings in Christchurch were pulled down anyway as engineers were reluctant to vouch for their structural integrity after the earthquake.'' 

''When it comes to saving lives, Christchurch gives us confidence that upgrading all vulnerable buildings to the current earthquake-prone building threshold [33 per cent] would be of major benefit.

''Other important measures we can be confident would save lives include bringing high-risk buildings not yet identified into the earthquake-prone building framework; and paying equal attention to other hazards from earthquakes such as landslides and collapsing cliffs,'' Mr Taig said. 

New Zealand has an estimated 15,000 to 25,000 buildings deemed to be likely to collapse in a moderate earthquake.

Mr Taig said the immediate focus should be on bringing vulnerable buildings up to the current earthquake-prone building threshold of 33 per cent of new building standard, rather than on raising that threshold.

The February 22 earthquake produced some of the most severe shaking recorded in any urban area in the world. In parts of Christchurch everything normally held down by gravity was effectively thrown up into the air, including buildings, people, cars and roads.  

Had the earthquake happened at night when more of the population was at home, there would have been considerably more fatalities in areas like the Port Hills. Several homes there were destroyed by collapsing slopes, and more than 50 homes were struck by boulders.

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- The Dominion Post

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