Staff with the City of Vancouver are hinting that they will be proposing a strategy to Vancouver City Council in 2025 to reduce the seismic risk of buildings, including potentially introducing changes to the Vancouver Building Code requiring more stringent building designs.
Such a strategy is being supported by the City’s release of the findings of an in-depth study, conducted in partnership with Natural Resources Canada, on the seismic risk of existing privately owned buildings across Vancouver.
According to this study, within the City of Vancouver’s jurisdiction, not including other areas of the Metro Vancouver region and British Columbia, a powerful earthquake could result in 6,100 completely and extensively damaged privately owned buildings and as many as 620 severe injuries and deaths if the seismic event occurred during the nighttime.
If the earthquake occurred during the daytime, the number of severe injuries and fatalities more than doubles to 1,370, during a period of the day when Vancouver — the region’s principal business, economic, cultural, entertainment, and tourism hub — is swelling with workers, students, and visitors from the suburban municipalities.
Furthermore, a nighttime earthquake would disrupt or displace 231,000 building occupants for more than 90 days, and this figure grows to 365,000 for a daytime earthquake. The direct financial losses would amount to $17 billion.
These figures are based on the scenario of a magnitude 7.2 earthquake with a nearby epicentre within the Strait of Georgia, just west of the University of British Columbia campus at the tip of the Burrard Peninsula.
Although the “Big One” earthquake with a magnitude of 8.0 or 9.0, triggered by the Cascadia Subduction Zone off the west of Vancouver Island, gets the most attention for being a possible major seismic event scenario in Metro Vancouver, the possibility of a local earthquake in the Strait of Georgia with a lower magnitude in the range of 7.0 could be more damaging for Vancouver.
In contrast, the 2001 earthquake that hit Puget Sound had a magnitude of 6.8, with an epicentre located only 60 km southwest of Seattle. It resulted in significant property and infrastructure damage, but its potential strength was blunted by the epicentre’s deep depth of 57 km below the surface.
Both the Puget Sound and Strait of Georgia earthquake scenarios are expected to occur at depths of 45 km to 70 km, and they are classified as “intraslab” earthquakes, which occur within the interior of a tectonic plate, as opposed to an “interplate” earthquake on the boundary of a tectonic plate (such as the Cascadia Subduction Zone).
Map of earthquake scenarios in the South Coast of BC. (City of Vancouver)
According to Natural Resources Canada, the estimated likelihood of a powerful earthquake hitting Vancouver is a one-in-five chance within the next 50 years.
The study notes that there are currently about 90,000 privately owned buildings within Vancouver. Many of the buildings that would be severely damaged or destroyed in a powerful Strait of Georgia earthquake would be older concrete mid- and high-rise residential buildings located in the downtown Vancouver peninsula, including within the West End neighbourhood, where almost half of the buildings were built before 1990 when there were less robust seismic design considerations. Such older buildings with a higher seismic risk are also found in high numbers in the Fairview, Kitsilano, and Mount Pleasant neighbourhoods. Together, a big earthquake could displace as many as 85,000 residents living in these structures.
Combined, these older concrete mid- and high-rise residential structures account for 1% of the total privately owned buildings but are home to 20% of Vancouver’s population or about 125,000 residents. Nearly all of these residential buildings account for the vast majority of Vancouver’s secured purpose-built rental housing supply, and for this reason, it is expected a powerful earthquake could disproportionately impact renters, low-income individuals, seniors, visible minorities, and Indigenous people.
Older concrete mid- and high-rise commercial buildings in downtown Vancouver and Central Broadway are also at high risk, potentially displacing over 28,000 people.
Map of the relative risk of buildings in Vancouver. (City of Vancouver)
Map of concrete mid-rise and high-rise buildings in Vancouver. (City of Vancouver)
There are also high risks with unreinforced masonry of old brick buildings, especially those in the Downtown Eastside and Gastown, where many buildings were built a century ago or are older, including numerous SRO buildings. Nearly 24,000 people could be displaced.
Across the city, about 104,000 people could be displaced by damaged or destroyed wood-frame apartment buildings, while nearly 86,000 people could be displaced by unreinforced masonry, wood, and low-rise concrete commercial buildings.
Between 1970 and 1985, the building codes required seismic performance for once-in-100-year earthquakes. The previous once-in-475-year standard was in practice from 1985 to 2005 until the current once-in-2,475-year standard was adopted.
Currently, the Vancouver Building Code requires seismic upgrades for many types of buildings when they are undergoing major renovations. But catalyzing and/or expanding the scenarios where seismic retrofits are required could be financially unattainable and displace residents and small businesses.
“Reducing seismic risk in existing private buildings is achievable, but reducing risk while balancing displacement and affordability impacts will be challenging. Nevertheless, careful and strategic action that complements ongoing development and building safety improvements undertaken each year can significantly reduce risk over time,” reads a City staff report.
“Cities along the West Coast, such as San Francisco and Los Angeles, have significantly reduced risk using long-term 25–30-year strategies while others, like Seattle, have begun reducing risk using at-risk building inventories.”
After the 2001 Puget Sound earthquake damaged the Alaskan Way Viaduct on the downtown Seattle waterfront, the City of Seattle and the Washington State Department of Transportation embarked on a multibillion-dollar project to demolish the seismically vulnerable viaduct and replace it with an underground highway and at-grade arterial road. The new tunnelled highway opened in 2019, at which point the viaduct was demolished. The City of Vancouver has used a similar seismic safety rationale for its uncertain plan to demolish the Dunsmuir and Georgia viaducts.
Another major area of seismic vulnerability is Vancouver’s aging public school buildings. The Government of British Columbia began upgrading or replacing seismically at-risk schools across the province in the 2000s, including 86 schools within Vancouver. So far, 40 schools in Vancouver have been upgraded or replaced, and it is expected this effort will reach full completion by 2030.
As of 2022, all three SkyTrain lines in the region are directly linked to earthquake early-warning sensors, providing valuable seconds, perhaps even minutes, to enable life-saving earthquake procedures that slow down trains and hold trains at stations.