Crunching the numbers over quake risk

By John Archer


Our house is right beside a big earthquake fault line here at Ohakune.

On Google Earth, you can see it running 26km from nearby Soldiers' Rd to Erua.

So I'm glad I live in a strongly built little house with the roof held to the floor by 3m-long bolts, and piles going right down to bedrock.

On the other hand, I've been practising for a Christmas pantomime in Raetihi's biggest and ricketiest heritage building, the Theatre Royal. It has a large sign at its main entrance: "All older buildings are classed as an earthquake risk and the Theatre Royal is no exception. So you enter at your own risk."

About 40 of us, aged from 7 to 70, have spent about five hours a week there for the past three months.

We weighed up the risk of an earthquake taking our lives, and the children's, against the enormous social and cultural benefits of this activity to all the participants, and to the community. Assuming we have a major shake here about once every 250 years, then there was about one chance in 20,000 of the building collapsing during the 100 hours we were in it.

I took that chance, but I would not work in the Royal all day every day, and I certainly would not allow children to be in there every day.

Those who are concerned about Wanganui city's heritage buildings can use a similar analysis to weigh the benefits and risks of their use.

The website of Wanganui District Council states that earthquake damage was done to Wanganui buildings in 1843, 1848, 1855, 1897, 1934 and 1991, with severe damage in 1844 and 1855.

On that basis there is a likelihood of an injury-dealing quake in Wanganui about once every 26 years (230,000 hours) and a life-threatening earthquake about once every 85 years (750,000 hours).

A typical tourist might spend 10 hours in and around those buildings, so his risk of being in harm's way in an injury-causing earthquake is about one in 23,000. But a worker who spends his working week in one of them for five years (10,000 hours) has about one chance in 23 of being in a injury-causing quake and one in 75 of being in a killer quake.

Anyone who lives full-time there for five years has about one chance in eight of being in an injury-causing quake.

And any object stored in one of these buildings for the next 85 years faces a very high chance indeed of being destroyed.

So casual visitors to Wanganui's old buildings are relatively safe, but workers and occupants run a significant risk. Tenants, prospective employees, tourists, shoppers and teachers planning class trips can weigh up the risks for themselves.

What are the heritage buildings that give Wanganui its unique tourist-attracting Edwardian look, and also give it this earthquake risk?

Its cultural buildings, the museum, art gallery, opera house, Alexander Library building and war memorial tower? Putiki Church? Do they include those commercial buildings along Taupo Quay and the lower end of Victoria Ave? And the classrooms, dormitories and chapel of Collegiate School?

I went to school at the old St Augustine's, next to the Alexander Library, the regional museum and Sarjeant Gallery, and two blocks away from the Opera House. Frequent visits to all these institutions played a valuable part in my formation.

However, it was what was provided inside the buildings that was valuable, not their faux-baroque exteriors.

I was entranced by the marble wrestlers at the Sarjeant, and by two paintings on its walls; men pouring molten steel and girls peeping over a garden wall. But on recent visits I've not been so impressed. Teachers can feel safe enough taking a class there for a brief visit, but it might be better to take their students to the Auckland art gallery to give them a real appreciation of New Zealand and European art.

I went to so many live shows at the Opera House in the 1950s. Amdram musicals, Shakespeare and Shaw presented by the NZ Players, amateur concerts, one-act plays, the National Orchestra and even one opera, Susanna's Cigarette. We explored its labyrinthine backstage passages when we sang, danced and shot up each other in school shows and plays.

The Drew Museum - now the Whanganui Regional - was an Aladdin's cave to me when we visited it during a school trip from Mangamahu in 1949. Suddenly I knew how my colonial forebears had lived, how the people living at Mangamahu 200 years previously had caught wild game, dug the soil, cut down trees and built houses. I learned about the bird life on our hills before all the forests were chopped down, and from the portraits on its walls and sculptured forms in its cabinets I received a finer appreciation of art than what I got from the Sergeant.

As a child, I thought that every city had a similar museum and I did not realise how much we owed to the generosity of local iwi and the foresight of Samuel Drew.

Our regional museum is world-class, so much better than the Te Papa amusement centre. If you want to give your children a real appreciation of our history and pre-history, the Wanganui and Hawera museums are the ones to visit, repeatedly.

I'm so pleased that the museum has had earthquake-resistant extensions added to it, where many of its priceless and unique artifacts can be stored safely, and where school children can be educated about our past without risk.

Like Michael Laws, I do not agree with compulsory strengthening of old buildings. It is financially impossible. But I think owners of rickety old buildings must be honest with those who spend money in them. I think that on every building and footpath in Wanganui where there is an earthquake risk there should be a warning sign similar to the one on Raetihi's Theatre Royal, perhaps with the additional note that the risk of injury is less than one in 200,000 for every hour spent there.

I think Wanganui's tourist advertising should carry the same warning. Perhaps visits to these old buildings could be promoted as another form of adventure tourism, with entrepreneurs selling T-shirts that boasted "I visited Wanganui's 5 per cent safe Old Town and survived."

I think employees who are hired to work in those rickety buildings should get paid danger money, and the small businessmen who lease these premises from absentee owners should get a rent reduction to compensate them for the payment of this danger money. I think the council should charge higher rates on an old commercial buildings to pay for the future cost of removing the rubble and bodies when its frontage falls on to the public way. I think that parents should be told of the risks and permission obtained before a school visit to a heritage building.

And I don't don't think anyone should worry if the Opera House, the Alexander and the Sarjeant fall down in the next quake, as long as their oldest paintings and documents are safe inside archival cabinets. If the council can get earthquake money, I think it should be first spent on strengthening or rebuilding the front of the Drew Museum. The Whanganui region owes this duty to future generations; we hold a world heritage collection in our care.

John Archer lives in Ohakune and shares his views with readers, coloured by his love of the mountain life.

- WANGANUI CHRONICLE

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