That sinking feeling

Hard lessons from Christchurch’s quake continue to hit home

A portion of the Geoscience Map 2000-3a

Last Friday’s earthquake near Port Hardy reminds us all to prepare for the big one. But while most of us think about surviving the first 72 hours, many of the serious consequences are much further down the road. Christchurch, New Zealand has proven a useful case study for what to expect.

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One year after the first of three earthquakes to hit Christchurch, New Zealand, thousands of residents are only now learning the true impact of the disaster on their lives.

Whole neighbourhoods must be simply abandoned because the soil has been rated unfit for remediation or uninsurable.

It’s a sobering scene brought home to Victoria, which is Christchurch’s sister city in many ways, including its population, the age of its architecture and the importance of tourism.

Emergency planners for Victoria and Saanich travelled to New Zealand twice to get a first-hand perspective. They delivered their message Thursday to a unique audience: councils from both municipalities, who combined their meeting for the first time to deal with issues of regional significance.

One lesson learned is the significance of soil type.

Maps of high-risk soil zones proved to be a fairly accurate predictor of damage to buildings and pipes.

Where retrofitted, underground infrastructure performed fairly well, said Brock Henson of the Saanich Emergency Program. Soil type, however, was a more important factor in whether water, sewer and storm pipes sustained damage during the quake, he added.

Similar maps exist of Greater Victoria, which identify areas subject to a risk of liquefaction.

The term refers to the water in the soil that’s squeezed out to the surface during an earthquake.

Robert Johns, with the Victoria Emergency Management Agency, saw instances in Christchurch.

“You see these big sand boils that bubbled out of the ground … It almost looks like at a beach when a clam will create a little hole and a little mound around it.”

When under a building, however, these boils can buckle the foundation.

In Christchurch today, much of the downtown is still closed and 60,000 people have moved away. The loss of revenue for the city is spurring layoffs. Some heritage buildings have seen their insurance skyrocket from $3,000 to $30,000.

Houses that appeared at first to stand up well to the quakes must be demolished because they’re no longer functional.  “The doors don’t close, the windows don’t open,” said Johns. “It wasn’t economical to try to fix them … In many of the areas they’re finding out now that the house they’re in has to be torn down or the neighbourhood has to be basically closed.”

The delay is due to the continual aftershocks, and the sheer number of buildings requiring inspection.

“We learned that a medium- and long-term housing solution is needed,” said Henson. Also needed is more expertise in rapid damage assessment.

The good news is that Victoria has fewer areas of gravelly or sandy soil, which is more susceptible to ground shaking. Johns said he wouldn’t expect to see any neighbourhoods abandoned here should a really strong earthquake hit. But there will likely be pockets of damage in every neighbourhood.

Low to medium risk zones include portions of Fairfield encompassing the heart of Cook Street Village.

Most of Victoria’s high and very high risk areas sit on old-fill hugging the waterfront, such as Ogden Point, Rock Bay,   the ferry terminals along Belleville Street, and the Empress and Victoria Conference Centre near the Inner Harbour.

A large portion of Vic West adjacent to the Gorge Waterway is also in the red, including two major ongoing developments, Dockside Green and Railyards.

Their location, however, doesn’t mean they’re doomed.

“Those buildings … are engineered for the soil type there,” Johns said. “They’ll anchor the building very deep.”

Factors that cause damage are numerous. The size, location and depth of the earthquake, the ground conditions, the construction type and age of the building, said Johns. “Some of it’s nature and some of it’s man.”

Insurance options can vary by area.

Some insurance companies restrict earthquake insurance based on postal code, said Rosslyn Milne, a branch manager with Megson FitzPatrick Insurance.

Within the Victoria region, however, such restrictions are rare, she said.

 

 

 

 

 

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