A Massive Fault Line Was Supposed to Be ‘Dead’. It Sure Seems Like It’s Stirring Again.

Here’s what you’ll learn when you read this story:

The Tintina fault is thought to have been inactive for more than 40 million years, but new research suggests that earthquakes occurred in the zone much more recently.
Researchers from the University of Victoria identified fault scarps that suggest major slips occurred during the Quaternary period (2.6 million years ago to present day).
The team estimated that the fault accumulates.2 to.8 millimeters of strain each year, meaning that a release could cause a 7.5 magnitude earthquake—or on that’s even bigger.

Earthquakes occur when two blocks of earth slip past one another at a fault. While earthquakes are perhaps the most tangible reminder that the ground we stand on is always shifting, not all movement at fault planes is sudden. Sometimes blocks slowly creep past each other across centuries. Some faults, like the Tintina fault, are believed to be inactive, meaning that they no longer have earthquakes. The Tintina fault stretches about 1,000 kilometers (621 miles) across the Yukon territory in northwestern Canada, and until recently, scientists believed the zone to have been inactive for over 40 million years.

A new study published in the journal Geophysical Research Letters, however, tells a different story. The research team—led by experts from the University of Victoria (UVic)—discovered a 130 kilometer (80 mile) stretch with evidence of recent movement. Now, experts believe devastating earthquakes could be on the way.

The team used high-resolution topographic data and LiDAR surveys collected from satellites, airplanes, and drones to identify fault scarps (linear ruptures produced by landscapes) in the area. Researchers found a series of fault scarps passing within 20 kilometers (12 miles) of Dawson City, Canada—evidence that could completely change our understanding of the Tintina fault’s movement.

“Over the past couple of decades there have been a few small earthquakes of magnitude 3 to 4 detected along the Tintina fault, but nothing to suggest it is capable of large ruptures,” Theron Finley, lead author of the study, said in a press release. “The expanding availability of high-resolution data prompted us to re-examine the fault, looking for evidence of prehistoric earthquakes in the landscape.”

Along the fault scarps, the team found 2.6-million-year-old glacial landforms offset by approximately 1000 meters (3280 feet). Researchers also discovered other 132,000-year-old landforms that were only offset by 75 meters (246 feet). Both findings confirm that the fault slipped substantially during earthquakes in the Quaternary period—a geological timeframe spanning from 2.6 million years ago to present day. Interestingly, landforms that emerged 12,000 years ago showed no movement, meaning that there haven’t been any large ruptures in the area for over 12 millennia.

Using the data collected, researchers estimate that the fault accumulates about.2 to.8 millimeters of strain every year, which could mean that a devastating earthquake is imminent.

“We determined that future earthquakes on the Tintina fault could exceed magnitude 7.5,” Finley said in the release. “Based on the data, we think that the fault may be at a relatively late stage of a seismic cycle, having accrued a slip deficit, or build-up of strain, of six metres in the last 12,000 years. If this were to be released, it would cause a significant earthquake.”

Earthquakes with a magnitude of 3.5 or higher are typically noticeable, but cause little damage. Once an earthquake reaches a magnitude of 6.1, however, it can do damage to poorly constructed buildings. As Finley explained, the Tintina fault may exceed magnitude 7.5, meaning that it would be considered a “major” earthquake on the magnitude scale, and could cause major damage across larger areas.

According to the press release, Canada’s National Seismic Hazard Model (NSHM) doesn’t currently recognize the Tintina fault as a discrete seismogenic fault source.

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