Everything is calm in James Bay as morning dawns. Thousands of people begin their daily rituals in the mundane rhythm of modern life: alarms ding, showers sputter, coffee grinders buzz.

Suddenly, disaster strikes.

Hundreds of kilometers away, a massive fault line off the coast of Vancouver Island ruptures like a gigantic zipper, unleashing enormous amounts of destructive energy across the region.

A magnitude-9 earthquake rips across Victoria. The ground shakes violently for two to three minutes, causing severe structural damage to thousands of buildings. Water and sewer systems collapse, as pipes burst in a fit of seismic power. Thousands of people are left without homes.

This is the ‘Big One’ – also known as a Cascadia subduction or megathrust earthquake – and it is just one scenario outlined in a new report commissioned by the City of Victoria on the seismic vulnerability of buildings and infrastructure, like water and sewage pipelines.

Lucinda Leonard, an assistant professor of geophysics at the University of Victoria’s School of Earth and Ocean Sciences (SEOS), specializing in earthquake and tsunami hazard assessment, called the report a wake-up call.

 “We cannot afford to ignore seismic risk,” she said. “It is really important that people take that onboard and really believe that this is something that is going to happen. The first step to being prepared is to really believe it will happen.”

Combined seismic risk of buildings over 50 years. Maps should not be used to assess the vulnerability of individual buildings. Source: VC Structural Dynamics report.

The City’s report examined three types of earthquakes that could hit Victoria over the next 50 years to assess the combined level of risk facing the city. It found that 30 per cent of Victoria’s buildings – nearly 4,000 properties – have a more than five per cent chance of “complete damage” during that time frame. Complete damage means buildings will have either fully or partially collapsed following an earthquake, or will not be safe to enter and require demolition.  

When the authors looked at the possibility of a future megathrust event, they found a ten per cent chance of occurrence during that same 50-year period, the highest likelihood of any class of earthquake examined.

But according to both Leonard and her colleague Edwin Nissen, an associate professor at SEOS studying earthquakes and active tectonics, the latest scientific research puts that number even higher, at 15 per cent over 50 years.

 “The science is changing fairly rapidly,” explained Nissen. “These great subduction earthquakes in Cascadia were only first recognized in 1987, so we’ve only known that they even exist for 30 years.”

Subduction earthquakes occur when one tectonic plate is pushed below another. Over hundreds of years, massive amounts of energy are built up and eventually released in the form of a megathrust event, the world’s largest class of earthquake.

The Cascadia Subduction Zone is located off Vancouver Island and extends more than 1,000 kilometers south to Northern California. The last subduction earthquake to hit Vancouver Island struck on Jan. 26, 1700. Exactly when and how strong the next will be is uncertain, but scientists have determined they occur on average every 450 years.

Despite this uncertainty, experts can assess how vulnerable a city may be given the likelihood of a future earthquake. The report presented to the City of Victoria outlined significant risks facing large portions of the existing building stock and other infrastructure.

In a subduction earthquake, the study predicted about 20 per cent of Victoria’s water pipelines would retain normal serviceability, while “sewer pipelines may be lost completely.” Nearly 40 per cent of all buildings could suffer either “extensive” or “complete” damage, meaning they would be “red-tagged” as too dangerous to enter.

James Bay is particularly vulnerable, in part due to underlying soils that can amplify the destructive force of an earthquake. In addition, much of the building stock in James Bay was built before 1972, when the National Building Code of Canada updated its seismic standards.

Buildings built prior to this time that have high seismic risk include unreinforced masonry of all heights; three- to four-storey wood apartment buildings; and mid- and high-rise apartments built on soft soil. Single-family wood homes constructed prior to 1960 are also vulnerable.

The consultants who wrote the report – VC Structural Dynamics – recommended the City refine its soil maps to identify high-risk areas, and carry out detailed assessments of at-risk buildings. They further advised the City to set up a Technical Advisory Board to develop and implement a seismic risk mitigation plan, and to replace vulnerable sections of the sewer system.

Professor Nissen said there is still research to be done to understand how local geology will affect the extent of damage. He said the consultant’s recommendations were a good start.

“You’re saving a lot of money in the long-run if you spend a little bit of money on these seismic hazard maps and then focus your subsequent efforts geographically and really target the places that are most at need,” he said.

City staff presented their own report to Council in February that recommended expanding the City’s Tax Incentive Program (TIP) to heritage buildings beyond the downtown core; examining the City’s authority to expand incentives to non-heritage structures; and looking at including seismic considerations in the City’s rental retention and revitalization study. The report did not include the recommendations from the consultant’s study.

Since 1999, TIP has incentivized 43 heritage building upgrades, with three new applicants each year, according to City staff. The seismic report presented to the City looked at more than 13,000 properties, and noted that about 80 per cent of those were built before 1972, making them vulnerable to damage in an earthquake.

Building damage in magnitude -9 subduction earthquake. Maps should not be used to assess the vulnerability of an individual building. Siurce: VC Structural Dynamics report.

Victoria Councillor Geoff Young told the Beacon renewing the city’s building stock will take time and involves complicated trade-offs.

 “The reality is that it’s too big a problem to address all at once,” he said. “The building stock has been built up over a century or so, and as it gets renewed the issue is being addressed to a large degree, certainly in terms of seismic stability … but there’s no question that it’s going to take a long time to address all the problems.”

“One of the realities is that, as you have a lot of turnover in the building stock and intensification and higher density buildings, you get a natural renewal of the housing stock. So although people bemoan the loss of older buildings, the offsetting benefit is that we get safer buildings,” he added.

Young said he weighs these trade-offs before making judgments about heritage preservation at the Council table. Affordability is an added concern, he said, when seismic retrofits of buildings lead to higher rents, or even ‘renovictions,’ for those living in older apartments.

Despite the scope of the issues facing the city and the region around earthquake preparedness, Professor Leonard maintains that Victorians need not despair.

“A lot of this might lead people to feel kind of hopeless [but] there’s a lot that people can actually do, even if it seems that there’s so much to be done and it takes so long to get the city really ready,” she said. “Even if a big earthquake were to happen tomorrow, you can work on your personal preparedness, in terms of knowing what to do during an earthquake. There are things you can do to secure the contents of your home because a lot of the time its things falling on people that will hurt them.”

To find more information on how to be prepared in an earthquake, visit www2.gov.bc.ca/gov/content/safety/emergency-preparedness-response-recovery/preparedbc/know-the-risks/earthquakes