Tectonic tremors detected between Victoria and Seattle


WATCH: They are a critical tool for studying earthquakes. There have been hundreds of tiny tremors between Victoria and Seattle this week and they are happening beneath our feet. Mary Griffin tells us what those rumblings teach scientists about the “Big One”.


This week, there have been hundreds of tiny tremors between Victoria and Seattle.
Seismologist Honn Kao with Natural Resources Canada described the cluster of tremors as an Episodic Tremor and Slip (ETS).

“The area between the brittle zone and the tactile zone is what we call the ETS zone,” Kao said.He said ETS is not earthquakes but a shaking event. The events occur every 14 months and last for weeks. During that time, the Cascadian subduction zone, which runs from Vancouver Island to northern California, slowly slips. These ETS events occur because Vancouver Island is slightly moving to the west. It nudges up against the locked fault zone. These nudges add to the energy stored in the fault.

“That creeping of the formation will eventually transfer stress upward to this locked zone. So that over a long period of time, it will exceed its strength and break,” Dr. Kao said.

“That’s the push back, that’s when the mega-thrust earthquake happens,” Dr.Kao said.

First discovered by researchers at the Pacific Northwest Seismic Network in 2003, this ETS events is happening over the next few weeks. And they’re regarded as critical tools for preparing for the mega-thrust earthquake that will hit the west coast.

At the emergency supply retailer, Total Prepare, there are ample supplies for any event, according to employee Zenia Platten.

There are devices for clean drinking water, for example.

“If the mega thrust happens, the roads are out, the ferries are out. We’re not getting supplies. Help is stopping in Vancouver and Seattle. We’re going to have to fend for ourselves,” Platten said.

Scientists say these tectonic tremors are a reminder that the west coast is in an active seismic zone.

Mary GriffinMary Griffin

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