Quake loss likely to be same here

Dunedin's heritage buildings would bear the brunt of a 7.1 magnitude earthquake centred on the city, with damage likely to be the same as in Christchurch, a seismic expert says.

The warning came as Dunedin City Council civil defence and rural fires manager Neil Brown said a team of about 40 building inspectors from Dunedin would travel to Christchurch if required in coming days or weeks.

The team, comprising council building inspectors and consultants, was one of only two in New Zealand to have taken part in a trial of new post-earthquake building assessment training earlier this year, Mr Brown said.

The programme was adapted from training given to authorities in California, in the United States, he said.

The other New Zealand team was already based in Christchurch.

Opus International technical services manager Ian Walsh, of Dunedin, told the Otago Daily Times a 7.1 magnitude earthquake would take a "very similar" toll on Dunedin's heritage buildings.

"We would expect to see some significant distress on that type of building, which would be those that would be around the old commercial areas of Dunedin, where those buildings are still present," he said.

It appeared modern buildings had withstood the Canterbury earthquake "perfectly well", but older un-reinforced masonry buildings had proved "extremely vulnerable" to modest ground movement, he said.

Reclaimed areas of Dunedin would be vulnerable to liquefaction - turning solid ground into a liquid state - including South Dunedin and areas around the Forsyth Barr Stadium site, he said.

However, the stadium's modern construction standards, including piles penetrating more than 20m into bedrock, would ensure it withstood an earthquake, even if the ground around the venue was badly affected, he said.

Mr Brown believed Dunedin was as well prepared for a major earthquake as Christchurch, with the same planning exercises undertaken to identify vulnerable points and critical infrastructure.

The offer to assist Canterbury Civil Defence authorities had been made through the Civil Defence national crisis management centre in Wellington, and could be taken up as Canterbury's staff began to tire, he said.

The earthquake underscored New Zealand's earthquake risk was not just centred on Wellington.

"I think it's a wake-up call to say nowhere in New Zealand ... can consider itself to be immune to this sort of thing," Mr Brown said.

 

Probably none

Probably none - they were driven with a pile driver, not with a rock drill - I can't imagine they drilled 60ft of rock out from under each each pile. More likely the piles are into sand and mud forming 2 rafts that the 2 sides of the stadium floats on top of - a quake will see them move relative to each other. The playing field is below ground level so it's likely to suffer the sort of liquefaction eruptions we've seen in Christchurch.

Dunedin's hills will both help and hurt us in an earthquake - we have lots of houses on bedrock which is a good thing but being on a slope they're on piles, brick piles - even the wooden houses. On the other hand South Dunedin is at least as susceptible to liquefaction as the worst parts of Christchurch.

 

20m into bedrock

Can we have an official count of just how many piles actually go 20m into bedrock, please?
I really would like to believe some do.

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