Lake Erie earthquakes caused by a changing water level? Study finds no smoke gun, urges further research

Seismogram of the June 10, 2019 Lake Erie earthquake of magnitude 4.0, which was recorded at the University of Michigan Seismic Station in Ann Arbor. Image credit: University of Michigan

In June 2019, a 4.0-magnitude earthquake occurred under Lake Erie off the coast of Ohio, about 20 miles northeast of Cleveland.

Although no damage was reported, the quake was felt widely underwater within 60 miles — throughout northeastern Ohio and in parts of Pennsylvania, Ontario and southeastern Michigan.

The earthquake and several aftershocks occurred near the end of a period of record increases in the Great Lakes and coincided with the highest water level ever recorded in Lake Erie. Could there be a relationship between the seismic activity of Lake Erie and the fluctuation of water levels in the lake?

To find out, University of Michigan researchers and colleagues compiled a new catalog of 437 relatively small earthquakes in the Lake Erie region that occurred between 2013 and 2020 — the most complete catalog ever obtained. All of the earthquakes were smaller than the June 2019 event, and most likely went unnoticed by area residents.

The researchers then calculated the stresses that Lake Erie water level change would transfer to faults in the rocks under the lake and used various statistical methods to look for a relationship between seismic rates and water levels.

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“It is not possible to prove a definitive correlation between the rate of earthquakes and water level or the rate of water level change,” said geophysicist UM Yihe Huang, co-author of a study published online May 9 in Seismological Research Letters.

The lack of a smoke gun may be in part due to the limited number of earthquakes in the new catalog, according to the researchers. Also, the stress changes that Lake Erie creates on nearby earthquake faults are likely ten or a hundred times smaller than those seen in places – such as the reservoir behind India’s massive Kwena Dam – where earthquakes have been blamed for altering water levels.

“We cannot completely rule out the effect of the water level increase on the reactivation of faults that hosted the 2019 Ohio earthquake sequence,” said study lead author Dongdong Yao, a former UM Postdoctoral Research Fellow who is currently at China University of Geosciences.

“Our results highlight the need to increase the intensity of close seismic monitoring of the lake to further investigate the effect of changing water loading on shallow fault reactivation in this region.”

To follow up on their findings, Huang and her colleagues will use new techniques to monitor regional earthquakes in the Great Lakes region and run physics-based simulations. specially:

Huang and seismologist Zack Spica at UM plan to conduct a field experiment this summer to convert a fiber-optic cable in Lake Ontario into sensors that can monitor earthquakes and other phenomena such as shocks, undercurrents or changes in water level. Previous studies in other parts of the country have shown that existing networks of fibre-optic cables — the same optical fibers that provide high-speed internet and high-definition video to our homes — can be used to study earthquakes. Huang and colleagues will simulate the additional stresses on Lake Erie earthquake faults caused by rising water levels, as well as the degree to which lake water seeping into the shale can help soften those faults. “These two effects may compete with each other in nature, and physics-based simulations can help us identify the most significant effect,” she said.

In addition, Huang and her team are still analyzing data from a network of eight seismometers, known as the LEEP Project for the Lake Erie Earthquake Experiment, which they ran in the western corner of Lake Erie from October 2018 to July 2021.

The Great Lakes region is generally considered to be seismically inactive, and earthquakes of magnitude 5 or more are rare. However, earthquakes greater than magnitude 2 occur two or three times a year in the region, particularly around Lakes Erie and Ontario. Earthquakes of magnitude 2.5 to 3 are the smallest of earthquakes that are generally felt by people.

“We are not sure whether faults in the Lake Erie region can produce destructive or even fatal earthquakes,” said Huang, assistant professor in the Department of Earth and Environmental Sciences at Imperial University. “That’s why seismologists are interested in studying the sequence of a type 4 earthquake from this region.”

Since the early 2010s, eastern Ohio has seen a significant increase in the frequency of relatively small earthquakes. The origins of those earthquakes are not well understood, but some previous studies have indicated that they can be traced to sewage injection and hydraulic fracturing activities.

Injection-induced earthquakes have also been suggested as a trigger for the recent 5-magnitude zone earthquake, which occurred in January 1986 in northeastern Ohio, east of Cleveland in southern Lake County.

Study area map. The red circles indicate the 27 indexed earthquakes that were used as templates in the study. The inset upper right shows water levels in Lake Erie between 2005 and 2020, with the 2019 magnitude 4 earthquake marked with a red star. Gray triangles show seismograph stations. Image credit: From Yao et al. In Earthquake Research Letters, 2022

In the new study, covering the period from 2013 to 2020, the UM-led team found a cluster of earthquakes in the vicinity of the 1986 earthquake and near sewage disposal wells that were operating during the study period. They concluded that this group of earthquakes “may have been caused by sewage disposal.”

“Most interestingly, the 1986 earthquake was also occurring during another period of high water levels recorded across the Great Lakes,” the authors wrote. “However, given the large distance relative to Lake Erie, it would be difficult to assess the effect of the lake-induced stress change on causing the 1986 earthquake.”

To create a new catalog of 437 Lake Erie region earthquakes, the researchers started with 27 previously reported earthquakes included in the comprehensive earthquake catalog of the National Advanced Earthquake System, which is known as the Komcat Catalog.

US seismological networks captured continuous recordings of ground motions in the area during the study period. Using the waveforms produced by the 27 known earthquakes as templates, the team scanned the continuous recordings for previously undetected earthquakes with similar waveforms. The process is called template matching.

Most of the earthquakes in the new catalog will not be felt by residents of the area and can only be detected by nearby seismographs sensitive to trace amounts of ground shaking.

The new catalog revealed 20 to 40 small earthquakes annually during the study period, which preceded the June 2019 event. The high seismic rate in 2019 was dominated by aftershocks in the aftermath of the 4.0-magnitude earthquake.

In addition to compiling the comprehensive new catalog, the team was also the first to map the fault rupture to produce the 2019 earthquake, which occurred at a depth of about 2 kilometers (1.2 miles).

In addition to Yao and Huang, the authors of the Seismology Research Letters paper are Liang Xue of Bowling Green State University and Syracuse University, Yuning Fu of Bowling Green State University, Andrew Grunewold of the University of Michigan Department of Earth and Environmental Sciences and School of Environment and Sustainability, and Jeffrey Fox of the Natural Resources Department at Ohio. Funding for Yao and Huang was provided by the University of Michigan.

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