Research maps ‘megathrust’ quake zone off northern B.C., however danger could also be far in future

Scientists have captured the primary detailed photos of the assembly of two tectonic plates off the coast of northern British Columbia, an space they are saying has the potential to generate the biggest “megathrust” earthquakes and tsunamis.

The photos verify what seems to be a uncommon geological prevalence, a subduction zone in its “infancy,” the examine by U.S. and Canadian researchers reveals.

The paper, within the peer-reviewed journal Science Advances, says the Queen Charlotte plate boundary options the beginnings of such a zone, the place one plate slides below the opposite.

The plate boundary that extends from the southern tip of Haida Gwaii to southeast Alaska was the positioning of Canada’s two largest earthquakes in latest historical past — a magnitude-8.1 quake in 1949 and the magnitude-7.8 quake in 2012.

Co-author Michael Bostock, a professor within the division of earth, ocean and atmospheric sciences on the University of B.C., says it’s possible the realm will see extra “thrust” quakes, and the subsequent one may very well be bigger because the fault grows.

The excellent news for folks dwelling on B.C.’s north coast, he says, is {that a} quake of comparable magnitude to the one in 2012 isn’t possible for a number of hundred years.

“In a sense, the concern is passed, at least for the next few generations of people.”

The quake in 1949 was brought on by tectonic plates transferring aspect by aspect alongside a fault, often called a “strike-slip” earthquake. These are far much less prone to produce tsunamis.

The 2012 quake, in the meantime, bore hallmarks of subduction, which produces the biggest megathrust quakes. But till the examine printed final month, there was no detailed imaging confirming it, says Bostock.

“Megathrust is just a fancy name for a thrust fault, a shallow-dipping thrust fault, where subduction is taking place. So, yes, what we’re imaging here is a nascent megathrust.”

Recent megathrust earthquakes embody final month’s 8.8-magnitude quake off the coast of southeast Russia, and the large quakes that triggered devastating tsunamis off Japan in 2011 and Indonesia in 2004.

Prior to the 2012 quake off Haida Gwaii, researchers had been debating whether or not subduction was a characteristic of the Queen Charlotte plate boundary, Bostock says.

The quake strongly advised an “under-thrusting fault,” and the detailed imaging has confirmed it, he says.

“The geometry of the Haida Gwaii thrust suggests that larger thrust earthquakes could nucleate along the margin and that tsunamis could be more common, both of which substantially increase the hazard of the region,” the paper says.

The website is a “rare example” of the beginnings of subduction, with the imaging “capturing this fundamental tectonic process in its infancy,” it says.

Still, it says the way forward for the Queen Charlotte plate boundary is unsure.

“While it has efficiently evolved to its current state, subduction initiation can fail at any stage before self-sustained subduction is reached; thus, the (plate boundary) evolving to this point does not guarantee a future outcome,” the paper says.

Bostock says there’s debate about how rapidly the Pacific plate is transferring into the North American plate, however it’s someplace between 1/2 and a couple of 1/2 centimetres per 12 months, alongside a roughly 200-kilometre stretch off the Haida Gwaii coast.

By distinction, the Cascadia subduction zone spans about 1,000 kilometres from northern Vancouver Island to northern California, and the tectonic plates are converging at a quicker fee, nearer to 4 centimetres per 12 months, he says.

The Cascadia zone is predicted to provide an enormous quake someday within the subsequent 200 to 500 years — however that’s not going on the Haida Gwaii website, Bostock says.

“So, because it’s a smaller fault area, and because the convergence is smaller, something like half as much as it is in Cascadia … we’re not likely to have another big (megathrust) earthquake off of Haida Gwaii in the near future.”

The comparatively smaller measurement of the fault off Haida Gwaii limits the scale of quakes it might produce, Bostock provides.

The 7.8 quake in 2012 is “probably as big as we’re likely to get, unless the zone grows bigger,” which it might do over an extended time period, he says.

The quake in 2012 rattled a lot of north-central B.C., together with Haida Gwaii, Prince Rupert and Quesnel, and triggered a tsunami warning for coastal areas.

It additionally altered the move and temperature of culturally vital sizzling springs on a small island throughout the southeast Haida Gwaii archipelago.

Lindsay Worthington, one other co-author of the paper, says the positioning presents a “natural laboratory” for the examine of plate boundaries, describing it as “one of the only places on the planet” the place researchers can observe subduction in its infancy.

The photos had been captured in “unprecedented” element by dragging a 15-kilometre-long hydrophone array behind a ship.

“Without knowing really what the subsurface looks like, there’s only so much that you can infer,” says Worthington, a professor within the division of earth and planetary sciences on the University of New Mexico.

“Now that we have these pretty definite geometries … we can have better understanding of what types of events happened in the past, and then that gives you insights into what’s possible in the future.”

While a large earthquake just isn’t imminent off Haida Gwaii, Worthington says the Queen Charlotte plate boundary continues to be “the largest natural hazard in Canada.”

This report by The Canadian Press was first printed Aug. 11, 2025.

Brenna Owen, The Canadian Press