The Tintina fault, which spans over 1,000 kilometers across northwestern Canada, was long believed to have been dormant for millions of years. But new high-resolution imaging from satellites, airplanes, and drones tells a different story. Beneath the forests and permafrost near Dawson City, researchers have uncovered surface scars, physical evidence of massive prehistoric earthquakes that tore through the Earth in the not-so-distant past.
Now, scientists are warning that this “long-forgotten” fault may be capable of unleashing a magnitude 7.5 or greater earthquake, potentially one of the most powerful in Canadian history.
“This fault has been silently accumulating tectonic strain for over 12,000 years,” said Dr. Theron Finley, UVic geologist and lead author of the study published in Geophysical Research Letters. “That strain is going to release at some point and when it does, it could be catastrophic.”
A geological sleeping giant
The Tintina fault is a major lateral strike-slip fault, the kind of fault that moves horizontally, like California’s San Andreas. Throughout its lifetime, it has slipped over 450 kilometers, but researchers believed its activity ceased tens of millions of years ago.
That belief has now been overturned.
Using lidar (light detection and ranging) mounted on drones and aircraft, as well as data from the ArcticDEM satellite elevation project, the research team identified a 130-kilometer-long segment of the fault showing unmistakable signs of repeated seismic ruptures during the Quaternary Period (2.6 million years ago to present).
Some of the fault scarps, narrow ridges that mark the surface rupture of past earthquakes, were found to have offset glacial landforms by up to 1,000 meters. More recent features, about 132,000 years old, were displaced by 75 meters, proving that the fault has remained active into Canada’s recent geologic history.
But the most startling revelation came when the team examined younger landforms, around 12,000 years old, that appeared undisturbed.
“That tells us the last major rupture occurred just before 12,000 years ago,” Finley explained. “And based on the current rate of tectonic strain accumulation, estimated at 0.2 to 0.8 mm per year, we believe the fault may now be nearing the end of a seismic cycle.”
In plain terms, a significant amount of energy has built up underground. If released in a single event, it could trigger an earthquake measuring 7.5 or greater on the Richter scale, capable of causing widespread devastation.
The implications are particularly dire for Dawson City, a historic town located within 20 kilometers of the newly identified fault scarps. Known more for its Gold Rush past than for seismic activity, the region lacks the kind of earthquake-resistant infrastructure common in places like British Columbia or California.
The threat doesn’t end with shaking. The surrounding landscape is highly prone to landslides, many of which are already unstable. Two major slopes, the Moosehide landslide to the north of Dawson City and the Sunnydale landslide across the Yukon River, are showing signs of ongoing motion. A strong quake could send millions of tons of earth cascading into nearby valleys or rivers, potentially blocking waterways, destroying property, and endangering lives.
National seismic blind spot
Perhaps most troubling is the fact that the Tintina fault is not currently recognized as an active seismic source in Canada’s National Seismic Hazard Model (NSHM), the model that underpins building codes and engineering standards across the country.
That is now expected to change.
Officials at Natural Resources Canada have confirmed that the data from the new study will be used to revise the NSHM. These revisions could have far-reaching impacts on everything from construction permits and zoning regulations to emergency planning and national infrastructure projects.
The findings are also being shared with local authorities, First Nations governments, and emergency managers across the Yukon, including the Tr’ondëk Hwëch’in and Na-Cho Nyäk Dun, on whose traditional territories the research took place.
While there’s no way to predict precisely when the next earthquake will strike, the science suggests that the conditions for a major rupture are already in place.
“This fault has been silent for over 12,000 years,” said Finley. “That’s well within the recurrence interval for a fault of this size and behavior. It’s not a question of if, it’s a question of when.”
Without immediate action to update hazard maps, strengthen infrastructure, and prepare northern communities, experts warn that Canada could face a disaster on a scale not seen in modern history.