Minutes after a powerful 9.0 magnitude earthquake hits off the coast of Vancouver Island during a summer day, a devastating scenario unfolds where thousands of individuals in British Columbia are either deceased or injured in the aftermath. The situation escalates with a tsunami, subsequent aftershocks, and widespread disorder.
Overwhelmed survivors flood hospitals in search of missing family members. The earthquake damages road and rail connections, followed by flooding from the tsunami. This leads to shortages of essential supplies like food and medical resources.
A detailed B.C. government risk assessment depicts the impact of a “megathrust” earthquake, projecting over 3,400 fatalities and more than 10,000 injuries on the day of the primary tremor. The report anticipates additional casualties and destruction from secondary events triggered by the earthquake such as tsunamis, aftershocks, and fires.
The analysis outlines staggering costs of $128 billion, the destruction of 18,000 structures, and significant damage to 10,000 more buildings. Economic growth is forecasted to halve, with long-term consequences on GDP and employment extending over the next decade. The report suggests that the losses would surpass the combined effects of all disasters experienced in B.C. over the past two centuries.
It highlights that Vancouver Island and a coastal region stretching approximately 20 kilometers from the U.S. border to the Sunshine Coast, including Vancouver, could face the most severe damage. This assessment is part of the broader B.C. disaster and climate risk evaluation from October 2025, which also identifies other extreme scenarios like severe flooding in the Fraser Valley and urban interface fires.
Edwin Nissen, an earth and ocean sciences professor at the University of Victoria, explains that the report’s projections on fatalities and property damage are based on simulations. The simulations account for factors like the type of buildings, their location, materials, and compliance with building codes in determining their vulnerability to seismic activity.
Nissen emphasizes the importance of regular updates to such reports due to the evolving nature of scientific and engineering knowledge. Uncertainties exist in the estimates, influenced by variables such as the time and season of an earthquake occurrence, with winter earthquakes posing higher risks due to water saturation in the ground.
According to the report, the last major earthquake comparable to the projected scenario occurred in 1700. Researchers have gathered information about this event from oral histories of First Nations communities and scientific studies of the Cascadia fault, which spans 1,000 kilometers from mid-to-northern Vancouver Island to Northern California.
The report suggests a 2 to 10 percent likelihood of a similar extreme event within the next three decades, citing the 2004 Indian Ocean earthquake as a comparable event in terms of tectonic characteristics and impact. Nissen warns that while historical records offer insights, the unpredictability of earthquakes means such events do not follow a fixed schedule.
Nissen points out the limited data on moderate earthquakes in the Cascadia subduction zone, leading to uncertainty about the region’s seismic activity. He stresses the need for preparedness, highlighting the potential for significant seismic events to occur at any time.