A new study out of the University of Victoria has found that earthquakes within 100 km of Greater Vancouver could be amplified by at much as four times due to the shape of the Georgia Basin.
Earthquakes are nothing new to those in Vancouver; the Pacific Coast is the most earthquake-prone area in Canada. In the past 70 years, more than 100 earthquakes of magnitude five or more have been recorded.
READ MORE: Earthquakes in Canada
But the shape of the Georgia Basin — a deposit of sedimentary rock in British Columbia that extends from roughly the middle of Vancouver Island inland to east of Whistler — could highly influence how the shaking is felt on the ground.
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Previous damage estimates did not account for this.
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“For a magnitude seven earthquake within 100 kilometres of Vancouver, we were seeing that the presence of the basin increases shaking by a factor of three or four. So if the basin hadn’t been there, then the level of shaking would be, say, a one or something,” said Sheri Molnar, one of the researchers of the study who is now a post-doctoral fellow at the University of British Columbia.
The energy an earthquake releases is measured in magnitudes. The intensity of an earthquake is used to describe how the earthquake feels.
When earthquakes occur, the waves of vibration travel up to the surface, which passes through material that is less dense. As the wave grows in amplitude, it bounces around both vertically and side-to-side. The particular shape of the Georgia Basin causes these waves to be focused and amplified.
Still, how the earthquake is felt depends on how deep into the ground it is.
“The level of shaking is kind of moderate or light in terms of if the earthquake was quite deep because it’s already far enough away that the level of shaking decreases by the time it gets to the surface,” Molnar told Global News. “But if it’s a shallow earthquake, then the level of shaking will likely be quite strong.”
The study also found that the earthquakes that would cause the most damage would be those coming from around 50 km south-southwest of the city.
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