Graphic by Mary Robertson (Production Assistant)
According to the current earthquake media frenzy, experts are claiming that impending events will rip open the earth “like a zipper.” Unfortunately for residents near the Juan de Fuca plate, which runs from Vancouver Island to northern California, these experts are coming to the same conclusion—a large, damaging earthquake in our lifetime is inevitable.
Lucinda Leonard, an assistant professor of Geophysics at UVic’s School of Earth and Ocean Sciences, explains that the Vancouver Island area has the highest earthquake hazard in Canada.
“It’s a reality that we live in an earthquake zone. We’ve had them in the past, and we will have them in the future, and we can expect tsunamis,” Leonard said. “Really, the question is: how prepared are we? It’s inevitable.”
Seismic activity is analyzed by looking at the next 50 years, which points to a 10 per cent earthquake probability. According to marked sediments left behind by past seismic events, a major magnitude nine earthquake tends to occur every 350–500 years. If we factor in the last intense tremor more than 350 years ago in 1700, and minor earthquakes that have occurred since then, the probability increases.
“There’s a very significant probability of a large earthquake occurring within our lifetime,” said Leonard.
Beyond the immediate danger of an earthquake, tsunamis are another concern. Leonard was involved in research on the tsunami in Haida Gwaii in 2012, the result of a magnitude 7.8 earthquake in the region. “You have a very large area of the sea floor that moves very suddenly and displaces the entire water column above the seafloor, and that’s what generates those really large tsunamis,” she said. Landslides that fall into bodies of water, including lakes, can also cause a tsunami.
Experts are aware of the risks and the possible damage, but is Vancouver Island sufficiently prepared? Leonard explains that studying smaller earthquakes in the area, identifying active faults, and monitoring the stress between them can help “estimate the maximum-sized earthquakes on those faults—we can also estimate how often we can expect those earthquakes.”
On the technical side, Benoît Pirenne, the director of User Services at UVic’s Ocean Networks Canada, leads a project that aims to notify subscribers of an imminent earthquake. “What we’re talking about here is a few seconds—30–90 seconds, depending on where the earthquake epicentre is, in respect to the assets that these companies might want to protect,” he said.
Statistics around the world prove that most earthquake casualties and injuries are not due to the shaking itself, but to the aftermath. This includes fires and explosions, for example, caused by open gas valves that could not be closed in time. Pirenne’s computerized system aims to solve this problem. The system has already been established in locations like Mexico City, Romania, Japan, and the state of California. Pirenne is leading the installation for areas in Greater Vancouver and Greater Victoria.
When an earthquake occurs, two different waves are propelled from the epicentre at different velocities: the first wave being the faster and immediate pressure wave; and the second being the seismic wave, which travels slower and produces the shaking.
Detecting the pressure wave allows Pirenne’s system to understand where the epicentre is located, gauge the magnitude of the earthquake, and send this information to subscribers 30–90 seconds before the shaking begins.
“Computers will have to be pre-programmed to act upon the alert that we might be sending,” said Pirenne. “This notification will be adapted to the needs of the organization that will implement it.”
This notification could stop the Vancouver SkyTrain, call back an elevator, turn on a red light at the entrance of a massive tunnel, and so on. “The whole point of these seconds of pre-warning is to offer to these people and organizations [the ability] to mitigate the risks,” Pirenne said.
