British Columbia

Tiny tremors push Vancouver Island away from B.C. mainland

Share on Facebook Share on Twitter Share by Email

Seismologist says the shift is known as an episodic tremor, and it happens every 14 or 15 months

Vancouver Island has moved about half a centimetre from the mainland in recent weeks. (Google Earth)

A series of small tremors over the last few weeks have pushed Vancouver Island away from the B.C. mainland, according to a federal scientist.

John Cassidy, a seismologist with Natural Resources Canada, said the shift is known as an episodic tremor, and it happens every 14 or 15 months.

"Over the past few weeks the southern half of Vancouver Island has actually moved about four or five millimetres to the west towards Japan. It's something that happens around the world in similar tectonic settings," Cassidy told CBC.

ADVERTISEMENT

The movement happens when the Juan de Fuca tectonic plate, which sits off the coast, sinks beneath the North American plate, where the island is located.

There's some concern from seismologists that a massive earthquake could happen during one of these events.

The two plates meet along the Cascadia Subduction Zone, a 1,000-kilometre-long fault that runs from northern Vancouver Island to northern California.

The Juan de Fuca plate is being forced underneath the North American plate, but a section of that boundary has become locked together, which means the plates are no longer sliding smoothly.

All the energy from that movement is being stored up inside the rocks, waiting for the moment it will be released as a catastrophic megathrust earthquake — otherwise known as "The Big One."