Dormant no more: Fault line risks major earthquake

A fault line long believed to be dormant could pose a significant earthquake threat to parts of Canada and the United States, according to a new study. The Tintina fault stretches roughly 600 miles from northeastern British Columbia into Alaska and was previously thought to have been inactive for about 40 million years. However, research published this month in Geophysical Research Letters reveals signs of far more recent movement.

Fault line

Using new topographic data from satellites, airplanes and drones, scientists identified an 80-mile segment of the fault where geological formations aged between 2.6 million and 132,000 years have been shifted laterally. “We further show that the fault has not ruptured in a major earthquake for at least 12 thousand years, and could generate an earthquake of at least magnitude 7.5 in the future,” the study stated. “The Tintina fault therefore represents an important, previously unrecognized, seismic hazard to the region.”

Earthquake

According to Michigan Tech, earthquakes measuring between 7.0 and 7.9 in magnitude are considered significant and can cause severe damage. Such events are rare, with only 10 to 15 occurring globally each year. Earthquakes of magnitude 8 or higher typically strike once every one or two years and can devastate communities near the epicenter. “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 meters in the last 12,000 years,” said Theron Finley, a recent University of Victoria PhD graduate and lead author of the study, in an interview with SciTechDaily. “If this were to be released, it would cause a significant earthquake.” Seismologists warn that tremors from the fault could be felt across British Columbia, Alberta and Montana. “It is one of the least studied fault systems in North America, and that needs to change,” said Dr. Michael West, state seismologist at the Alaska Earthquake Center

Quake monitoring

First identified in 1912 by geologist J. B. Tyrrell in the Yukon Territory, the Tintina fault has largely been ignored by quake monitors and hazard maps due to its long period of inactivity. Scientists now describe it as a mature, slow-moving fault — one that remains silent for thousands of years before suddenly producing a major earthquake. “The most dangerous thing is not just that the fault is active,” West said. “It is that no one’s been paying attention to it.”

Past earthquakes

The study’s mapping revealed ancient glacial landforms shifted sideways by nearly 3,200 feet, indicating powerful past earthquakes. These findings suggest the fault has ruptured multiple times, with the last major event occurring more than 12,000 years ago. While the landscape shows no recent movement, experts say the lack of activity means the fault has been steadily building pressure. “We are not good at thinking about things that happen every 12,000 years,” West noted. “But over that time, it builds up enough motion to create a 7.5 magnitude of quake.”

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