Assessing the Risk of Earthquakes in Metro Vancouver

On October 4, 2023, a magnitude 3.5 earthquake struck near Metro Vancouver, following a similar tremor detected on September 26. Experts indicate that while many small quakes occur regularly, recent seismic activity raises concerns about future, potentially stronger earthquakes. John Clague, Professor Emeritus at Simon Fraser University, notes the increased potential for local quakes, emphasizing that larger events like the anticipated ‘Big One’ remain uncertain and infrequent, though smaller damaging earthquakes are plausible.

On Friday, October 4, residents of Metro Vancouver experienced a minor earthquake registering a magnitude of 3.5, which originated approximately 18 kilometers west of Delta and east of Ladysmith, British Columbia, at a depth of 65 kilometers. This seismic event occurred shortly after 2 a.m., sparking concerns regarding the likelihood of a more significant earthquake occurring in the near future. Just days prior, on September 26, a 3.8-magnitude earthquake struck near Haro Strait at around 4 a.m., with its epicenter located 11 kilometers east of Sidney, well beneath Earth’s surface at a depth of nearly 55 kilometers. This tremor was felt by residents as far north as Nanaimo and Parksville on Vancouver Island, and extending to southern Washington State. Experts, including John Clague, Professor Emeritus at Simon Fraser University, indicate that while minor earthquakes happen daily in British Columbia—most registering below magnitude 1 and often unnoticed—the recent quake locations have instigated particular scrutiny. Professor Clague notes, “We have known for quite some time that these earthquakes occur beneath Puget Sound and we know that we get some beneath the Canadian border.” He emphasizes the importance of the proximity of these quakes to the Lower Mainland, suggesting a potential escalation in seismic activity close to metropolitan areas. He points out, “Maybe we could get an earthquake in Vancouver. The band of earthquakes can extend up,” acknowledging that while tremors with magnitudes of 3 or 4 typically do not result in damage, the possibility for more impactful events exists. The term “Big One” frequently induces anxiety among residents. While catastrophic magnitude 7 or larger earthquakes are inevitable, their timing remains uncertain. Instead, Professor Clague posits that smaller but significant earthquakes in Vancouver are more plausible than an immediate catastrophic event. “It does not mean that we are approaching a magnitude 7 or higher earthquake…it could be little bitty adjustments along the plate boundary,” he stated, adding that large, damaging earthquakes like the anticipated Big One, which would devastate large areas, tend to occur once every 400 to 500 years. Factors influencing the potential damage from an earthquake include its magnitude, proximity to populated areas, and depth. Clague explains that deeper quakes tend to cause less impact. He states, “Large and shallow tremors close to cities are the most damaging.” With respect to the timing of earthquakes, they are commonplace at any hour and tend to be underreported when they occur at night. The recent earthquakes, occurring around 2 a.m. and beneath a magnitude of 4, likely went unnoticed by many, as smaller quakes do not produce the prolonged ground motions characteristic of stronger events. The depth of these recent tremors also means their energy dissipated significantly by the time it reached the surface, making them less noticeable than other, shallower quakes. In summary, although Metro Vancouver experiences numerous minor tremors and increased seismic activity in the region raises questions about future earthquakes, it remains uncertain when and if a significant earthquake will strike. The geology of the area ensures a continued potential for seismic events, and as Professor Clague insightfully remarks, “We cannot do anything about it…Mother Nature’s game plan involves that collision of one plate against the other that can lead to periodic fracturing of the crust and movements along faults.”

The Pacific Northwest of North America, particularly British Columbia and Washington State, is known for its seismic activity due to the presence of several tectonic plates, namely the Juan de Fuca Plate and the North American Plate. The Cascadia subduction zone, where these plates meet, is a significant focus for earthquake studies, as the region has experienced major seismic events in the past. The community’s awareness of potential seismic hazards has increased significantly due to past events, including the notable earthquakes that could lead to widespread devastation, inciting public concern and a demand for thorough understanding of the geological activity in the region.

In conclusion, while Metro Vancouver has recently experienced minor earthquakes that raise concerns about future seismic activity, expert assessments suggest that significant events, while plausible, remain unpredictable in timing and magnitude. Residents are encouraged to maintain awareness of earthquake preparedness, as despite daily minor quakes, the risk of more significant tremors persists in this seismically active region. A profound understanding of the geological mechanisms underlying these phenomena remains crucial for public safety and preparedness.

Original Source: www.vancouverisawesome.com