Earthquake engineering

Chauvel should quit the earthquake predictions business

Just last week Charles Chauvel was telling everyone who would listen that the risk of an earthquake before Christmas was low:

“These buildings must have been considered safe last week, and the week before. The acting deputy secretary of courts says there is ‘no imminent danger’. Instead of this knee-jerk reaction, a proper risk assessment should apply.

“The courtrooms in these courthouses will be scheduled for skeleton sittings over those three or four weeks. The likelihood of a major quake in most of the affected locations between now and Christmas is low.

After last nights earthquake in the Wellington region it looks like Charles Chauvel’s earthquake predicting skills have as much credibility as his skills at winning Ohariu off Peter Dunne.

We were warned, especially on "heritage" buildings

The Herald carries a story about the warnings that have been around for years about Christchurch, and especially with regard to heritage buildings.

Warnings about the vulnerability of Christchurch’s heritage buildings in an earthquake were given 15 years ago on television.

The earthquake dangers facing Christchurch were examined in anInside New Zealand documentary broadcast on TV3 in 1996.

A clip from the documentary posted on YouTube on March 5 had received more than 3000 hits by yesterday.

The TV3 documentary described Christchurch as having “a fatal flaw.”

“It sits on a soft, shaky sponge of river stones and silt half a kilometre deep. In any decent quake, Christchurch will shake like a leaf,” it said.

Christchurch was described as having “quite a high susceptability to liquefaction”, especially in eastern areas.

Concern was also raised about the “hundreds” of old buildings that had not been strengthened.

The heritage list of old buildings “defined most of the earthquake-prone buildings” in Christchurch, one expert said.

Meanwhile, owners of earthquake-prone heritage buildings in the city were warned last year that they could have to pay at least $169 million for strengthening works – from 2012. The warning appeared in a story which ran in The Star in March, 2010.

Nearly 500 heritage buildings in Christchurch and on Banks Peninsula would have been required to be strengthened or demolished within 15 to 30 years under amendments proposed for the city council’s 2006 Earthquake-Prone, Dangerous and Insanitary Buildings Policy.

According to a review of the policy, these 490 buildings were only a fraction of about 7658 buildings in Christchurch that would be likely to collapse in a “moderate earthquake” – the equivalent of an earthquake with a magnitude around 6.5 on the Richter scale. Last month’s devastating quake in Christchurch measured 6.3.

And that number of 7658 is getting reasonably close to the 10,000 number used by John Key. I believe that the number is certainly going to be much more than 10,000. Some of the buildings shown int eh video clip are of course now rubble.