On December 6, Jan Dettmer was busy building his new home in Whitehorse, Yukon, when he felt the ground tremble beneath him. As a geoscience research manager for the Yukon Geological Survey, he quickly realized he was experiencing a significant earthquake—the largest he had ever faced.
“I actually went under a table,” Dettmer recalled. Thankfully, only a sheet of plywood fell. Damage across Yukon remained light, thanks to the quake’s epicenter being 250 kilometers away, beneath an ice-covered mountain range near the Alaskan border. This 7.0 magnitude quake was the strongest in Canada in over 75 years.
Months later, scientists are studying the earthquake and the more than 4,000 aftershocks that followed. They’ve uncovered crucial insights about the region’s geology and a new seismic risk linked to melting permafrost.
The area is home to two major fault systems: the Fairweather fault along the Pacific coast and the Denali fault further inland. Researchers believe a “connector” fault might lie between them, able to absorb energy from the Yakutat microplate beneath the North American continent. However, proving this is challenging due to the region’s glaciers and rugged terrain.
Julie Elliott, a geophysicist from Michigan State University, noted that the December quake’s epicenter aligned perfectly with the proposed connector fault. “Like a bright light switched on in a dark room,” she said, adding that this event revealed more about the hidden fault structure.
In a related analysis, scientists found that aftershocks clustered in two groups: one along the suspected connector fault and another suggesting a conjugate fault at a 60-degree angle. This information could help predict future earthquakes in the region.
Moreover, researchers are examining how seismic waves can cause uneven shaking. When waves transition from solid to loose soil, they can generate intense energy, affecting locations far from the quake’s epicenter. This risk is heightened as climate change worsens and permafrost thaws.
Dr. Jeremy Gosselin, also from the Geological Survey of Canada, indicated that the changing landscape may require updates to building codes to ensure safety during future quakes. “Thawing permafrost adds an extra layer of complexity,” he stated.
For Dettmer, the earthquake was a stark reminder of the unpredictable nature of the Earth. “It’s a good reality check,” he shared, highlighting how these experiences shape our understanding of working in a geologically active area.
With earthquakes like the one in December, it’s clear that the Yukon needs to prepare for future seismic events and the risks that come with climate change. Understanding geology today will help us create safer communities tomorrow.
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