B.C. earthquake highlights Vancouver’s vulnerability should the ‘Big One’ arrive

Downtown Vancouver is seen from the city's west side in this file photo. (Shutterstock.com)

The earthquake that rattled B.C.’s densely populated South Coast on Friday served as a sharp reminder that a large-scale seismic disaster still lurks, and much still needs to be done to adequately prepare for its predicted catastrophic impact.

The “Big One” is a potential 9.0 magnitude earthquake that is expected to hit the Cascadia fault line, running from northern California to British Columbia, and bring with it a succeeding tsunami that would devastate much of the Pacific Northwest.

Another predicted earthquake, less infamous than the “Big One,” is expected to be smaller in size but shallower, nearer to Vancouver, and much more damaging, according to UBC professor of structural engineering Dr. Perry Adebar.

“People tend not to talk about that one,” he says.

The chances of a large-magnitude earthquake occurring off the West Coast is considered to be a one in a 400-year occurrence, while “the really big one,” the smaller, shallower, but more devastating quake, is considered to be a one in 25,000-year chance, says Adebar.

The Geological Survey of Canada estimates a one in five chance of a damaging earthquake in the next 50 years.

The devastation of either would be astronomical.

According to the City of Vancouver, should a magnitude 7.2 earthquake hit the Strait of Georgia,13,000 buildings would be at least moderately damaged, and 6,000 of those would likely collapse or require demolition.

More than half of the city’s residents would be displaced. Over 4,500 residents could face injuries, with over 1,300 people expected to be seriously injured or killed.

Risk of structural damage

The last time Vancouver experienced an earthquake of such a scale as the predicted “Big One” was in the 1700s, and the largest earthquake felt this century was Vancouver Island’s magnitude 7.3 event in 1946.

From a structural standpoint, Adebar says there have been no large-scale events to determine how Vancouver’s current buildings would hold up in the midst of a quake and, given Vancouver’s buildings and the topography they sit upon are different to others around the world, there is limited precedent.

“If you have an earthquake come along and knock down a few of the really bad buildings, we know which [buildings] we need to look for, and we can do something. We’ve had none of the benefits of previous earthquakes helping us to learn what we need to do. It’s been quiet, and then all of a sudden one day, bam, it’s going to hit,” he said.

“There’s going to be really hard lessons learned.”

While seismic upgrades are still yet to be put to their full test, pinpointing the buildings that are of particular risk is a step in the right direction to ensuring the city is sufficiently safeguarded, says Adebar.

According to the city, neighbourhoods expected to be hit the hardest are the West End, Downtown, the Downtown Eastside, Strathcona, Fairview, Mount Pleasant, and Marpole. Those pockets of the city have the highest concentrations of older brick, concrete and wood buildings – especially mid-rise and high-rises apartment complexes.

Privately owned buildings

Adebar says the government is doing a “great job” trying to prepare for such a disaster - including the seismic upgrading of schools and public buildings - but it means little in light of the lacklustre efforts put into safeguarding privately owned buildings.

Those buildings, comprising much of the city’s residential and commercial properties, are “receiving no attention at all,” and would be hit the hardest if a large-scale earthquake were to hit, he says.

“When we talk about the Vancouver skyline, there are privately owned buildings with, what you might call, ignorant owners,” says Adebar.

“They are the ones that we spend a little bit now on and we can reduce that risk enormously … all it needs is a little intervention, and it’ll actually be usable after the earthquake, whereas we do nothing, and then it collapses, and kills all the occupants.”

Adebar says there should be a system in place where buildings are rated on their risk factor. Apartment inspections, he adds, would do well to include reports of the building’s current seismic standing.

“It is sad that we’re keeping everyone so ignorant,” he says.

“Nobody has been asking for that information. There are buildings that were built and met the building code at that time, and then after that, nobody asks any questions.”

These privately owned buildings are the focus of the City of Vancouver’s risk reduction strategy work this year, but the work to reduce such risk is “especially challenging,” the city said in a statement.

Considerations like affordability and tenant displacement, as well as regulatory and cost challenges, are some of the many concerns that arise with privately owned properties, it said.

Reminder to be prepared

Miranda Myles from Vancouver’s emergency management agency says the city’s preparedness for an earthquake is a continual process, and not a box that can be checked once completed. The same goes, she says, for the residents who may be feeling overwhelmed about their own levels of preparedness following the recent tremor.

“We know this topic can be daunting, and we really want to encourage people to take it just step-by-step based on where they’re at. Preparedness doesn’t have to be expensive. It doesn’t have to be time consuming,” she says.

Myles says having conversations with friends and family about the potential risks is “a huge step” to ensuring an emergency can be adapted to, and there are several small tasks, like packing an emergency kit, practising safety techniques and securing the home, that serve as manageable first steps.

The city holds regular sessions on the topic of preparedness through the Vancouver Public Library, and its recently launched interactive tool, the Hazard & Risk Explorer, has a great deal of information to peruse.

“Preparedness can be broken down into easy-to-tackle, bite-sized pieces. Things that are free, that are easy to do, can be where you start,” she said.

“Then, if you want to grow after that, you can. But those easy steps are super, super important.”