Great Lakes water levels are in flux. New research looks at how and if that could cause local earthquakes

The Great Lakes Climate Change Project is a joint initiative between CBC's Ontario stations to explore climate change from a provincial lens. Darius Mahdavi, a scientist with a degree in conservation biology and immunology and a minor in environmental biology from the University of Toronto, explains how issues related to climate change affect people, and explores solutions, especially in smaller cities and communities.

Earlier this month, parts of southern Ontario felt an earthquake that struck close to the nearby city of Buffalo, N.Y. 

"I woke up to it … I felt what I guess you would consider a small jolt and continuous shaking … about 15 to 20 seconds," St. Catharines, Ont., resident Stephen Murdoch told CBC Hamilton the morning of Feb. 6.

Earthquakes Canada monitored the magnitude 4.3 quake and said there were no reports of damage.

In another part of the world the same day, an unrelated, devastating 7.8 magnitude earthquake hit Turkey and Syria. The death toll has surpassed 40,000.

But while earthquakes in Ontario do not typically cause loss of life, they're more common than you might think, say scientists. 

Earthquakes, especially major ones, are caused by movement of tectonic plates, and scientists are constantly investigating the many factors that can lead to local seismic activity. 

Contributing factors include human activities such as mining, the injection of wastewater underground, and dam reservoirs that experience rapid and intense fluctuations in water level.

Now, scientists are investigating whether natural water level fluctuations — such as those brought on by climate change — correlate with regional seismic activity.

The research indicates some promising results in other locations, but scientists say more needs to be done to understand that correlation, and earthquakes in the Great Lakes area. 

Why earthquakes in Ontario are less intense

Most Ontario residents have likely never felt an earthquake because while dozens of seismic events occur each year, only a handful reach a magnitude that can be felt. 

Fault systems (the most common place for stress in the planet's crust to be released) around the Great Lakes are relatively inactive, according to experts. This is why we see fewer and less serious earthquakes than places on plate boundaries, like B.C. and California, or Turkey and Syria. 

However, minor earthquakes in Ontario aren't anything out of the ordinary, said Alexander Peace, a structural geologist at McMaster University in Hamilton. 

"Magnitude 3 [earthquakes are] quite common around here in the Great Lakes." 

As a result, scientists suspect ancient fault lines likely exist under all the Great Lakes, but they remain almost entirely unknown and unmapped.

"Historically this region was not well instrumented … there were not a lot of detections of earthquakes, which means that we didn't really know the faults very well in a lot of Great Lakes regions," said Yihe Huang, a seismologist at the University of Michigan who has conducted research on Great Lakes-area earthquakes. 

Though we don't consider the Great Lakes an area at risk of a major quake, there isn't enough data to say that conclusively. 

"We're actually just seeing a small snapshot of a very big process. Let's just say a fault has a recurrence interval of 1,000 years, just for example, and our instrumental record is 200 years long," said Peace. "We might not capture how often that fault produces a seismic event."

Researchers are working to improve detection of earthquakes through new technologies. They include the use of distributed acoustic sensing (DAS) technology to repurpose the sprawling network of fibre-optic cables used for telecommunications into an ultra-sensitive earthquake detection system. 

But anyone can contribute to this data collection, said Peace, by reporting on the Earthquakes Canada website whether you've felt a local earthquake and filling out a questionnaire.

Where the research is going next

Though science is still far from having the ability to predict earthquakes, certain human activities have long been known to induce local seismic activity due to altered stress levels on the Earth's crust. 

Mining is a frequent culprit, responsible for many small earthquakes, including two in the last year measuring magnitude 2.8 and 3.1, respectively, near Sudbury, Ont., according to Earthquakes Canada.

Fracking and wastewater injection — both activities involve pumping fluids down into the Earth's crust — are also a common cause, since it decreases the friction in underlying faults, allowing for greater movement, which can lead to earthquakes that exceed magnitude 4.0. 

Even the creation or destruction of large buildings can be enough to induce small but detectable seismic activity, said Peace. 

But another well-studied source is the active changing of water levels created by dams and the resulting human-made lakes. 

By rapidly draining or filling those reservoirs, the quick changes to the stress on the underlying crust can produce small localized earthquakes. 

Both low and high water levels can contribute to seismic activity, said experts, depending on the orientation of the underlying fault. 

Now, scientists are investigating whether natural fluctuations in water level, which are typically much less intense, can have that same impact. 

"It's the same idea for [Lake Erie]. If you are seeing rapid water level changes in the lake, then there is also more loading on these faults," said Huang.

According to researchers, the Great Lakes have seen record low and high water levels in the last two decades, including record highs in recent years for Lakes Superior, Erie and Ontario. An increase in the variability of water levels is expected in the future, they say.

This has already been observed elsewhere in the world. In East Africa, an area with much more active faults and a large lake system, researchers have found seasonal correlations between water levels and seismic activity. 

Great Lakes levels and quakes: Any link?

Since the Great Lakes area is naturally less seismically active, the relative contribution of water levels to generating earthquakes could be even greater, said Huang. 

Huang conducted a recent study to investigate whether there is a relationship between water levels in Lake Erie and local earthquakes, and it found no conclusive correlation.

But that doesn't rule out the possibility. 

She said the problem is twofold: Seismic activity here is smaller and harder to detect, and there simply aren't enough instruments taking measurements around the Great Lakes. The hope is DAS and fibre optics will help solve this problem for future studies. 

But even if the evidence grows with better data collection, it isn't like Ontario would suddenly be an earthquake hotspot. 

The effects would be highly localized and not typically felt over a broad area, said Allison Bent, a research seismologist with Earthquakes Canada. 

According to experts, this is not cause to worry about earthquakes ravaging Ontario, but it underscores how interconnected the planet's processes are and how little we understand about the impacts of our actions.

"It is a new topic and there may never be a completely definitive answer to it," said Bent. "But you know, if people start looking at it more, we have more data. It might start to lean more one way or the other."