Lake Erie quakes triggered by shifting water levels? Study finds no
smoking gun, urges further research

Date:
May 9, 2022
Source:
University of Michigan
Summary:
In June 2019, a magnitude 4.0 earthquake occurred beneath Lake
Erie just off the shoreline of Ohio, about 20 miles northeast
of Cleveland.



FULL STORY ==========================================================================
In June 2019, a magnitude 4.0 earthquake occurred beneath Lake Erie just
off the shoreline of Ohio, about 20 miles northeast of Cleveland.


========================================================================== Though no damages were reported, the underwater quake was widely felt
up to 60 miles away -- throughout northeastern Ohio and in parts of Pennsylvania, Ontario and southeastern Michigan.

The quake and numerous aftershocks occurred near the end of a period
of record- setting increases in Great Lakes water levels and coincided
with the highest water level ever recorded on Lake Erie. Could there be
a connection between Lake Erie seismicity and fluctuating water levels
in the lake? To find out, University of Michigan researchers and their colleagues compiled a new catalog of 437 relatively small Lake Erie-area earthquakes that occurred between 2013 and 2020 -- the most complete such catalog ever obtained. All of the quakes were smaller than the June 2019
event, and most were likely not noticed by residents of the region.

Then the researchers calculated the stresses that shifting Lake Erie
water levels would impart to faults in the rocks beneath the lake and
used various statistical methods to look for a correlation between
earthquake rates and water levels.

Their verdict?


==========================================================================
"No conclusive correlation could be established between earthquake
rate and water level or water-level change rate," said U-M geophysicist
Yihe Huang, co- author of a study published online May 9 in the journal Seismological Research Letters.

The lack of a smoking gun may be partly due to the limited number of earthquakes in the new catalog, according to the researchers. Also,
Lake Erie- induced stress changes on nearby earthquake faults are likely
10s or 100s of times smaller than those seen in places -- such as the
reservoir behind India's massive Koyna Dam -- where earthquakes have
been blamed on changing water levels.

"We cannot fully rule out the impact of increasing water level on
reactivating the faults that hosted the 2019 Ohio earthquake sequence,"
said study lead author Dongdong Yao, a former U-M postdoctoral research
fellow who is now at China University of Geosciences.

"Our results highlight the necessity of denser and closer monitoring
of lake seismicity to further investigate the impact of changing water
loading on reactivating shallow faults in this region." To follow up
on their findings, Huang and her colleagues will use novel techniques
to monitor Great Lakes regional seismology and will conduct physics-
based simulations. Specifically:
* Huang and U-M seismologist Zack Spica are planning a field
experiment
this summer to convert an existing fiber-optic cable in Lake Ontario
into sensors that can better monitor seismicity and other phenomena
such as seiches, bottom currents or water-level changes. Previous
studies in other parts of the country have demonstrated the
potential for using existing networks of fiber-optic cables --
the same optical fibers that deliver high-speed internet and HD
video to our homes -- to study earthquakes.

* Huang and colleagues will simulate the additional stresses on
Lake Erie-
area earthquake faults caused by high water levels, as well as
the degree to which lake water percolating into the bedrock may
help lubricate those faults. "These two effects may be competing
with each other in nature, and the physics-based simulations can
help us determine which effect is more important," she said.

In addition, Huang and her team are still analyzing data from a network
of eight seismometers, known as the LEEP project for Lake Erie Earthquake exPeriment, that they operated 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 greater are rare. However, earthquakes
with magnitudes greater than 2 occur two or three times a year in the
region, mainly around lakes Erie and Ontario. Earthquakes with magnitudes
of 2.5 to 3 are the smallest generally felt by people.

"We are not certain whether Lake Erie-area faults can produce destructive
or deadly earthquakes," said Huang, assistant professor in the U-M
Department of Earth and Environmental Sciences. "That's why seismologists
are interested in studying a magnitude 4-type earthquake sequence 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 poorly understood, but some previous studies
suggested they can be attributed to wastewater injection and hydraulic fracturing activities.

Injection-induced seismicity has also been suggested as the trigger for
the region's last magnitude 5 earthquake, which occurred in January 1986
in northeastern Ohio, east of Cleveland in southern Lake County.

In the new study, which covers the period from 2013 to 2020, the U-M-led
team found a cluster of earthquakes in the vicinity of the 1986 temblor
and near wastewater disposal wells that were operating during the study
period. They concluded that this cluster of quakes "might be potentially induced by wastewater disposal." "More intriguingly, the 1986 earthquake
was also happening during another period of recorded high-water levels
across the Great Lakes," the authors wrote. "However, due to a large
distance relative to Lake Erie, it would be difficult to evaluate the
impact of lake-induced stress change on triggering the 1986 earthquake."
To create their new catalog of 437 Lake Erie-area quakes, the researchers started with 27 previously reported earthquakes listed in the Advanced
National Seismic System Comprehensive Earthquake Catalog, which is known
as the ComCat catalog.

U.S. seismometer networks captured continuous recordings of ground motions
in the region during the study period. Using the waveforms produced by
the 27 known earthquakes as templates, the team scanned the continuous recordings in search of previously undetected earthquakes with similar waveforms. The process is called template matching.

Most of the earthquakes in the new catalog would not have been felt by
area residents and are only detectable by nearby seismometers sensitive
to tiny amounts of ground shaking.

The new catalog revealed 20 to 40 small earthquakes per year during the
study period, leading up to the June 2019 event. A high seismicity rate in
2019 was dominated by aftershocks following the magnitude 4.0 earthquake.

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

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


========================================================================== Story Source: Materials provided by University_of_Michigan. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Dongdong Yao, Yihe Huang, Liang Xue, Yuning Fu, Andrew Gronewold,
Jeffrey
L. Fox. Seismicity around Southern Lake Erie during 2013-2020
in Relation to Lake Water Level. Seismological Research Letters,
2022; DOI: 10.1785/ 0220210343 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/05/220509162412.htm

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