What if the earth under your feet was quietly accumulating enough energy to release a disaster of rare proportion in North America? Deep in the wilderness of Canada’s Yukon Territory, mounting geologic evidence indicates that the Tintina Fault long relegated to the inactive list could be gearing up for a big earthquake, one that might redefine both the physical landscape and the future of engineering and infrastructure in the region.
The Tintina Fault had for decades been considered a geological relic, with its most recent major activity believed to have taken place more than 40 million years ago. But a new study by Theron Finley of the University of Victoria has turned this supposition on its head. Employing a battery of contemporary remote sensing technologies satellite imagery, airborne and drone-based lidar scientists carefully charted a 130-kilometer stretch of the fault south of Dawson City. This high-resolution technique enabled them to look through dense forests and rough ground, and what they saw was a string of fault scarps: the unmistakable ground signatures of ancient earthquakes. As Finley described it, “The expanding availability of high-resolution data prompted us to re-examine the fault, looking for evidence of prehistoric earthquakes in the landscape.”
The geologic record exposed by the researchers is sobering. The 2.6 million-year-old glacial landforms were laterally displaced by a whopping 1,000 meters a witness to the terrific energy of the quakes of ancient times. The second scarp, which was 132,000 years old, had a 75-meter displacement. However, surprisingly, landforms younger than 12,000 years had no such displacement, suggesting a long phase of quietude in the Holocene period. This seeming tranquility, however, is illusory. As Finley cautioned, We concluded that subsequent earthquakes along the Tintina fault will be capable of greater than magnitude 7.5. From the data, we believe the fault is at a fairly late phase of a seismic cycle, having acquired a slip deficit, or strain build-up, of six metres over the past 12,000 years. If this were to be released, it would produce a large earthquake.
Such a slip deficit piling up at a rate of 0.2 to 0.8 millimeters per year means the fault is ready to move. The possible implications are dire. A magnitude 7.5 earthquake would not only put Dawson City, a town of 1,600, at risk, but also put highways, mining activities, and vital infrastructure across the Yukon at risk. The area’s vulnerability to landslides also increases the risk, as shown by the continued instability of the Moosehide and Sunnydale landslides close to Dawson. The interaction between ground shaking and slope collapse in permafrost terrains is especially dangerous, with potential for soil liquefaction and quick ground deformation a situation well recorded in the rest of the northern world like Alaska, where the 2002 Denali Fault earthquake caused extensive liquefaction and lateral spreading in zones of thawing permafrost liquefaction and lateral spreading were recorded extensively during the earthquake.
Detection and analysis of these early fault motions have been transformed with the help of improvements in lidar and drone-based remote sensing. In contrast to conventional mapping, lidar technology sends out laser pulses that pass through vegetation, creating accurate three-dimensional representations of the ground surface. It enables researchers to see subtle fault scarps sometimes as little as a few meters high and wide trapped beneath dense boreal forests. As has been shown in other seismically active areas, including the Yangsan Fault in Korea, “topographic analysis using LiDAR data makes it possible to precisely trace faults,” providing a detail impossible with traditional techniques topographic analysis using LiDAR data makes it possible to precisely trace faults. In the Yukon, the resolution needed to map the scarps of the Tintina Fault within 20 kilometers of Dawson City was supplied by combining the ArcticDEM data with focused drone surveys a task unthinkable even a decade ago.
The implications here go far beyond the interests of scholars. Canada’s National Seismic Hazard Model, used to guide building codes and engineering practices across the country, has not hitherto identified the Tintina Fault as a distinct seismogenic source. That is about to change. The incorporation of this new information will redefine seismic risk evaluation, triggering revisions to infrastructure planning and emergency planning in Yukon and adjacent Alaska the results also will be disseminated to local governments and emergency managers to enhance earthquake preparedness in their jurisdictions.
For earth scientists and engineers, the Tintina Fault’s wake-up call is a sobering reminder of the difficulty of seismic hazard in cold, distant areas. The problems are further exacerbated by permafrost that can switch from a solid foundation to a cause of instability when it begins to thaw due to increased temperatures. With the thawing of permafrost, the likelihood of differential settlement, slope failure, and soil liquefaction rises, endangering building, road, and pipeline integrity the ground geohazards associated with them, such as differential settlement, slope instability, and liquefaction of rotten, unconsolidated material in seismically active warm permafrost areas, are major hazards to the built environment. Engineering solutions covering everything from deep pile foundations and above-ground structures to ground-freezing methods and sophisticated monitoring systems are being used to reduce these risks, but the uncertainty lies beneath.
In the end, the tale of the Tintina Fault is one of scientific stewardship and technological advancement. As Finley and his team have demonstrated, the deepest secrets of the earth can be revealed with the appropriate tools and those discoveries hold pressing lessons for communities sitting on the threshold of geological awareness.
