Wastewater from oil and sand caused a major earthquake in Alberta

A new study by researchers at Stanford University finds that one of the most powerful earthquakes ever recorded in Alberta, Canada, was likely caused by oil and gas activity.

View of the Peace River in northern Alberta, Canada. (Image credit: Shutterstock)

On November 30, 2022, a 5.6-magnitude earthquake rocked the remote Peace River region in northwest Alberta, part of Canada’s oil sands region. Although people felt the shaking more than 400 miles away, residents and businesses reported no injuries or damage.

Energy regulators in the region described the quake as a natural tectonic event. However, a rigorous new analysis by geophysicists at Stanford University indicates that oil industry activity — specifically, the dumping of sewage deep underground — likely triggered the quake. And three slightly smaller quakes hit the same area again on March 16, less than a mile away from last year’s large quake.

Researchers have long linked earthquakes to fracking and sewage disposal in other parts of Alberta and British Columbia, two provinces that straddle the Canadian Rockies. The new study, published March 23 in Geophysical Research Letters, is the first to link such a large earthquake to human activities far from the mountain range, in a region where industry is focused on exploiting oil sands rather than fracking for natural gas.

The findings have safety implications for ongoing and future energy-related operations, such as underground storage of carbon dioxide to help mitigate climate change.

“Earthquakes of similar magnitude to the Peace River event can be devastating, even deadly, if they occur in more densely populated areas,” said the study’s lead author Ryan Schultz, who recently completed a Ph.D. in geophysics at the Stanford Doerr School of Sustainability. “It is important that we understand the mechanisms involved and how to avoid triggering more of these events.”

“The Peace River earthquake caught our attention because it happened in such an unusual place,” said co-author William Ellsworth, research professor of geophysics and co-director of the Stanford Center for Induced and Operated Seisms. “Multiple lines of conclusive evidence indicate that this earthquake was man-made.”

Find the culprit

Over recent decades, scientists have documented hundreds of earthquakes caused by oil and gas operations around the world, especially in the United States. To assess the origins of the Peace River earthquake, the Stanford team and colleagues used a well-proven approach that takes into account details and context of seismic events, including location, depth, timing, regional history of background earthquakes, and records of industrial activity.

Injecting fluids increases pore pressure within the underlying crack, destabilizing it. The induced reverse slip (beach ball) lifts the upper layers, resulting in the ground deformation observed in the satellite imagery. (Image credit: Schultz et al., 2023)

Operations in the Nahr al-Salam area center on extracting a thick, black, viscous oil known as bitumen. To pack the tar-like substance to make it easier to pump to the surface, workers inject massive amounts of hot water or solvent underground, where it can mix with heavy metals, hydrocarbons, and harmful chemicals. The most economical way to dispose of this wastewater is to reinject it underground. Since bitumen recovery operations began in the Peace River Study Area in the 1980s, about 40,000 Olympic-size swimming pools (100 million cubic metres) of sewage have been injected underground.

The researchers compared publicly available information about Peace River sewage disposal activities with ground deformation measured by satellites and regional seismographs. “The Alberta government deserves credit for its transparency in providing public access to production and disposal data,” Ellsworth said. Overall, the results linked frequent minor earthquakes to wastewater disposal from bitumen recovery nearly a decade ago, strongly suggesting a major earthquake in November 2022 as well.

A major part of the evidence came from satellite observations, which showed a significant 3.4 cm rise in the ground at the time of the November earthquake. This change in elevation has proven to be compatible with seismic motion along a previously undocumented fault line – a fracture between giant blocks of rock deep in the Earth where most earthquakes occur. According to the study, the large volume of sewage increased water pressure on the crack, weakening it and making it prone to slipping.

earthquake risks in the future

The Peace River earthquake in 2022 is a “cautionary tale,” Schultz said, for a region where government and industry aim to expand hydrogen production and carbon capture and storage in coming years while continuing to dump oil sands wastewater.

One proposed approach to producing hydrogen involves splitting natural gas into hydrogen and carbon dioxide, then capturing the carbon dioxide and compressing it into a supercritical liquid for long-term storage. “Switching to ‘blue’ hydrogen will require disposal by injecting unprecedented amounts of supercritical carbon dioxide,” Schultz said. Like wastewater from bitumen production, the injection of carbon dioxide underground can trigger earthquakes.

Stanford researchers hope that expanded seismic monitoring at active petroleum recovery sites, at Peace River and elsewhere, will help scientists understand when and how human activity leads to earthquakes. “It is extremely important that we understand all aspects of induced earthquakes, from the underlying physical mechanisms to risk management,” Ellsworth said.

Co-authors include Stanford postdoctoral geophysicist Jeong-Ung Woo. Carissa Pepin, Ph.D. ’22; Howard Zipker, Professor of Electrical Engineering and Geophysics; and Paul Segal, Cecil H. and Ida M. Green Professor of Geophysics. Zebker is also an affiliate of the Stanford Woods Institute for the Environment. Additional co-authors are from the University of Alberta, Edmonton, and Canada Natural Resources.

This research was supported by the Stanford Center for Induced and Induced Earthquakes.

To read all the stories about science at Stanford, subscribe to the biweekly Stanford Science Digest.

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