A hidden tectonic fault in Canada’s Yukon, previously deemed inactive, may soon produce a major earthquake of at least magnitude 7.5, according to new research.
An extensive fault line known as the Tintina fault, stretching from northeastern British Columbia to central Alaska, has quietly accumulated strain over at least the last 12,000 years. Recent studies have revealed that this fault remains significantly active, challenging previous perceptions of its dormancy.
Researchers caution that predicting when the next significant earthquake will occur is impossible, but evidence suggests it is inevitable. Dr. Theron Finley, the lead author of the study published in Geophysical Research Letters, indicated to BBC Science Focus that their findings point to an active fault which continues to build up strain over time. “And so we anticipate that in the future, it will rupture again,” Finley said.
The Tintina fault is a classic example of a ‘right-lateral strike-slip fault’—a type of fault where two blocks of the Earth’s crust slide past each other horizontally. During an earthquake, if the opposite side of such a fault moves to the right, it exemplifies this right-lateral motion.
Historically, one side of the fault has shifted approximately 430 kilometers (around 270 miles), predominantly during the Eocene epoch, which occurred roughly 56 to 33.9 million years ago. During that era, it shifted at a rate of about 13 mm (0.5 inches) per year. Despite a few minor earthquakes ranging from magnitude three to four in the area, the Tintina fault was long thought dormant until recent technologies provided fresh insights.
Utilizing satellite surface models and drone-mounted Light Detection and Ranging (LIDAR), Finley’s team re-examined the fault, penetrating the dense forest to reveal traces of a seismically active past and what could be a similarly active future for the Yukon region.
Scattered fault scarps, which are narrow landforms formed when quakes rupture to the surface, were found across the landscape. While these scarps can extend for tens to hundreds of kilometers, they typically measure only a few meters in height and width. “In the case of the Tintina fault, the scarps appear as an interesting series of aligned mounds,” Dr. Finley noted.
Dating these features allowed researchers to discover that while the fault has experienced multiple ruptures over the past 2.6 million years, it has not produced a major earthquake in recent history, specifically the last 12,000 years. During this time, it has been accumulating strain at a pace of 0.2 to 0.8 mm (0.008 to 0.03 inches) annually.
Fortunately, the potentially affected area is sparsely populated. However, Finley warns that when the fault does eventually rupture, it could result in significant landslides, infrastructure damage, and adverse effects on nearby communities.
“I want to be clear that we don’t have a great sense of how imminent an earthquake is,” Finley emphasized. He stated that although a substantial period may have passed since the last major event, it remains unclear whether another is likely to occur imminently or far into the future.
With the fault now confirmed as active, the next research goal is to better estimate the frequency of large earthquakes at this site. While this won’t predict exact timings, it could provide a more reliable timeframe within which another large earthquake may be expected. “Earthquakes don’t necessarily occur periodically,” Finley stated, “but it would give us a better sense of how often we expect large earthquakes.” Nonetheless, any future activity on the Tintina fault is likely to result in a significant event.