On October 4, in the middle of the Strait of Georgia, approximately 30 km south-east from Nanaimo, a 3.5 magnitude earthquake was recorded. Two hours later, a 4.0 tremor was measured just west of Fort St. John in northern BC. On the very same day, another seismic event–one measured at a magnitude of 4.1–was recorded in the waters south of Haida Gwaii.

This isn’t an atypical week along British Columbia’s famed flaws—sorry, I mean faults.

And so, I think I speak for every reasonable west coaster when I ask…

HOLY SHIT, ARE WE ALL GOING TO DIE?

Well, no, not yet. We still have time. But, seriously, are we in immediate danger? Does this string of smaller earthquakes mean anything? What is a subduction zone, and why does it sound so scary?

They say ‘The Big One’—the long anticipated megathrust earthquake that has BC residents shaking in their boots—is inevitable, but the sort of inevitable that’s soon? Or the sort that’s ‘soon’?

Are you prepared if (or when) The Big One comes knocking? Or shaking?

British Columbia sits in an interesting position, tectonically speaking. The oceanic Juan de Fuca plate—considered a microplate, and one of the smallest in the world—is small compared to the continental North American plate it’s hurtling against at a rate of four centimetres per year.

What is now commonly referred to as one plate, the Juan de Fuca, is really three separate remnants of the ancient Farallon plate. Roughly three to four million years ago, the Juan de Fuca Plate fractured. The first of the two new plates, the Gorda plate, is found along the coast of northern California. The second, the Explorer plate, is to the west of Vancouver Island.

These two Juan de Fucan fractures are where most of the magic happens.

I guess I probably shouldn’t refer to potentially catastrophic natural disasters as magic, should I?

Anyway, a majority of seismic activity happens in the territory of these newer microplates. Where all these plates converge, a process called subduction has occurred.

When tectonic plates meet, one eventually has to give way and move under the other or subduct, recycling itself back into the Earth’s mantle. In this case, the denser oceanic Juan de Fuca plate and its fractures have subducted under the continental North American plate, and in doing so has created the Cascadia subduction zone, a nearly 1000 km long fault line that traces the BC coast down to northern California.

This subduction zone, especially in the areas of the Gorda and Explorer plates, is where the most danger lies. One ‘small’ slip and the subduction zone could bring forth a megathrust earthquake. And this is precisely why the North American west coast has become so seismically infamous—thanks to the Cascadia subduction zone.

But what about these recent earthquakes? Do they hint at anything bigger?

“The bottom line [is] that they are unlikely to be precursors to the ‘Big One’,” Tim Stokes, a professor of Earth Sciences at VIU tells me.

It’s hard to call it a reassurance, but British Columbia alone records thousands of earthquakes every year. In a tectonically active area like ours, it's a given.

So if the recent string of earthquakes isn’t anything to panic about, what about The Big One?

“What precursors to that event might be are hard to say, if they occur at all,” Stokes says.

Although it’s hard to pinpoint anything more specific, scientists anticipate that the long-awaited Cascadia megathrust earthquake—The Big One—is inevitable at some point within the next 200 years. For reference, 13 similar megathrust events have occurred along the Cascadia subduction zone over the last 6000 years—averaging out to one roughly every 500 years.

Whether it comes in our lifetime or in the next, it’s recommended that everyone does what they can to prepare

Do your research, know the risks, and consider throwing together an emergency kit just in case. With The Big One, it’s not a matter of if, it’s a matter of when.