After the event that killed thousands, injured tens of thousands and affected millions of Nepalese, a Berkeley seismologist spoke about preparations needed in regions with high seismic activity. Dr. Peggy Hellweg said:
Probably the most important factor in building collapses is the construction of the building, the structure. In general all buildings constructed in an old style, which is stone on stone; or stone, mortar and stone; are very, very susceptible to earthquakes.
Ten years ago, the BC’s provincial budget made this unequivocal commitment:
- “Funding is also provided to seismically upgrade all at-risk schools within 15 years.”
However, like many other Liberal promises, the words proved decidedly hollow. After years of administrative shuffling that delayed work on many high-risk schools, government recently announced a new completion target for seismic upgrades in schools. It is now 2030, or 2040, or some time afterward, depending on whether or not BC Place needs another new roof or if Site C and the LNG fantasies prove to be as costly as we fear.
Will there be a major earthquake that damages Canada’s westcoast? Of course. Scientists may be unsure of the exact time or place but geological evidence shows that over time, it is a certainty. From Natural Resources Canada:
From northern Vancouver Island, to the Queen Charlotte Islands, the oceanic Pacific plate is sliding to the northwest at about 6 cm/year relative to North America. The boundary between these two giant plates is the Queen Charlotte fault – Canada’s equivalent of the San Andreas fault. Canada’s largest historical earthquake- a magnitude 8.1, occurred along this fault on August 22, 1949. This earthquake, larger than the 1906 San Francisco earthquake, caused nearly a 500-km-long segment of the Queen Charlotte fault to break.
Cascadia Subduction Zone
West of Vancouver Island, and extending from the north tip of the Island to northern California, the oceanic Juan de Fuca plate is moving towards North America at about 2-5 cm/year. This region is called the Cascadia subduction zone. Here, the much smaller Juan de Fuca plate is sliding (subducting) beneath the continent (it is about 45 km beneath Victoria, and about 70 km beneath Vancouver). The ocean plate is not always moving though. There is good evidence that the Juan de Fuca and North America plates are currently locked together, causing strain to build up in the earth’s crust. It is this squeezing of the crust that causes the 300 or so small earthquakes that are located in southwestern British Columbia each year, and the less-frequent (once per decade, on average, damaging crustal earthquakes (e.g., a magnitude 7.3 earthquake on central Vancouver Island in 1946). At some time in the future, these plates will snap loose, generating a huge offshore “subduction” earthquake – one similar to the 1964 M=9.2 Alaska earthquake, or the 1960 M=9.5 Chile earthquake. Current crustal deformation measurements in this area provide evidence for this model. Geological evidence also indicates that huge subduction earthquakes have struck this coast every 300-800 years.
The last truly major event on Canada’s west coast was in January 1700, when a Cascadia subduction quake of estimated magnitude 9.0 caused widespread damage and a tsunami that reached Japan. However, experts predict an earthquake in the 6.5 to 7.5 range could strike at any time in southwest BC. This map prepared by the U.S. Geological Survey shows the areas most at risk from a significant seismic event in BC and Washington State. In 2001, the Nisqually earthquake in Puget Sound measured 6.8 and caused an estimated $2 billion in damages.
It is worth noting that the area of highest risk touches southern Vancouver Island where numerous schools are rated vulnerable to earthquake damage. Metro Vancouver, the location of most schools in need of modification or replacement, is assigned moderate risk of experiencing a significant earthquake by 2024.