With 325 years between coastal B.C. and its last subduction or megathrust earthquake, typical best describes 2024, says a seismologist with Natural Resources Canada.
Southwest B.C., where tectonic plates collide, is CanadaB次元官网网址檚 hotspot, seeing more than 1,200 earthquakes last year. Several were felt and most were offshore along the active faults.
B次元官网网址淭hereB次元官网网址檚 always something going on around here. We typically see tiny earthquakes each and every day people arenB次元官网网址檛 feeling,B次元官网网址 said John Cassidy.
ItB次元官网网址檚 an average number for the region, with most small or far enough away to not even be felt. Two deep quakes stand out because they were widely felt late in the year off Sidney and Tsawwassen.
On Sept. 26, a 3.8-magnitude earthquake hit nearly 60 km deep B次元官网网址 contributing to why thousands reported feeling it despite its weakness. It was lightly felt in Vancouver and Victoria, according to Earthquakes Canada, including up to the tip of the Saanich Peninsula and as far as Nanaimo to the north and Sooke to the west.
Eight days later, a similar quake was felt across the southwest, centred 18 km west of Tsawwassen.
B次元官网网址淚tB次元官网网址檚 pretty typical. These deep earthquakes are common in the area,B次元官网网址 Cassidy said.
B次元官网网址淏ut it is a complex region because we have different types of earthquakes,B次元官网网址 he added. B次元官网网址淲e have an ocean plate that is moving toward us four to six centimetres per year, thatB次元官网网址檚 about how fast your fingernails grow.B次元官网网址
Adding up to four to six metres of movement in 100 years, the plates are locked together, moving towards the area from the west. All the while, they're B次元官网网址渟toring energy for one of these big subduction earthquakes.B次元官网网址
While tiny earthquakes happen nearly every day, subduction earthquakes occur in the subduction zone, where two tectonic plates collide and one is forced beneath the other. The last was a magnitude 9 that struck in the year 1700.
Somewhere in the middle in terms of magnitude are the surface-to-30-km-deep earthquakes in the crust, like the two felt late last year, but closer to the surface. Those in the 4- to 6-magnitude range are capable of causing damage and occur every decade or so on the south coast.
None of them come with a warning.
B次元官网网址淭hereB次元官网网址檚 no signals or indications of when an earthquake will happen. We do have earthquake early warning systems in place now,B次元官网网址 Cassidy said.
The Earthquake Early Warning system, developed by Natural Resources Canada, became operational in B.C. in spring 2024. Almost 100 core stations work together to monitor for powerful earthquakes. Those larger than magnitude 5 and close enough to communities with systems in place will trigger the public system alert, similar to an Amber Alert.
B次元官网网址淒epending on how far away the earthquake is, it really controls how much warning time you have. For one of the deep earthquakes, the one off Sidney in October, you might have a five- or 10-second warning here in Victoria,B次元官网网址 Cassidy said.
The systems take advantage of the fact modern information sharing is even faster than the speedy three to four kilometres per second waves of an earthquake.
Being prepared ahead is just as critical as those seconds to minutes warning.
They include simple steps like keeping shoes and a flashlight by the bed, securing heavy wall hangings and bookshelves, and having the basic emergency kits and grab-and-go bags ready for any emergent situation.
These tips, for the CRD specifically, can be found at .
While a megathrust could be in natureB次元官网网址檚 works, the region is better prepared than ever, Cassidy said. There have been leaps and bounds in equipment and inter-agency collaboration, more and deeper data on the regular both around the world and locally and even building codes developed with earthquakes in mind.
B次元官网网址淭he science is advancing really quickly,B次元官网网址 he said. B次元官网网址淭hings are getting better all the time.B次元官网网址