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Hundreds of small tremors detected under Vancouver Island

Last Updated Sep 16, 2020 at 10:58 am PDT

Hundreds of small tremors have been detected under Vancouver Island over the past week. (Courtesy Pacific Northwest Seismic Network)

Hundreds of tiny seismic tremors have been detected under Vancouver Island over the past week

No one would have felt these tremors, a seismologist explains

Tremors could may be sign of Episodic Tremor and Slip, but not necessarily warning of "The Big One", seismologist says

VICTORIA (NEWS 1130) – Nobody will have felt it, but over the past week, more than 1,300 tiny seismic tremors have been detected under Vancouver Island.

Natural Resources Canada seismologist John Cassidy says the island is currently shifting slightly to and from the mainland.

“It’s this, almost like a tectonic dance. Vancouver Island is slowly moving to the east, but then over the course of two or three weeks, it moves backwards towards the ocean,” Cassidy explains, adding this may be a sign of an Episodic Tremor and Slip.

GEOFACT_Episodic Tremor and Slip ETS

“It’s very different from an earthquake where you see sort of this initial burst of energy and different types of waves will follow. This is more like a slow rumbling that’s really tiny. No body’s feeling this,” Cassidy adds, telling NEWS 1130.

Geologists have warned our region is overdue for a major earthquake. While not a specific sign of the impending “Big One,” Cassidy says researchers believe these events do put additional pressure on the major fault line off the west coast of the island.

ETS events typically happen every 14 to 15 months, however, he notes these kinds of tremors are happening a lot more frequently than was originally thought.

“So it’s almost a continuous process now from different areas along what we call the subduction zone, where an ocean plate is being pushed underneath North America,” Cassidy tells NEWS 1130.

He admits the island’s “dance” is still a bit of a mystery and was only discovered about 20 years ago. Cassidy explains Vancouver Island is actually moving closer to the mainland by about a centimetre each year.

“It decreases some of the stresses in the region where the slipping is taking place, which is typically around the central Vancouver Island region, but it also adds a tiny, tiny bit of stress to the region of the fault that isn’t slipping,” Cassidy says, adding the same process happens elsewhere in the world, too.