It was just a relatively small shake, an earthquake beneath Lake Erie that was a mild 3.1 magnitude that could be felt in some lakeshore communities.
Still, Ohio seems increasingly prone to the shakes; there have been 25 earthquakes of magnitude 2.0 or higher over the past two years, equal to the number the five years before that. There have been about as many such quakes in Ohio so far this decade as in the previous 30 years
“We think Ohio, especially northeast Ohio and Lake Erie, is going through a period of increased seismic activity,” said Mike Hansen, coordinator of the Ohio Seismic Network.
One explanation could be that there is better monitoring equipment than in the past. But more frequent activity is a likelihood.
Ohio State University geophysics professor Ralph Von Frese said location is the key.
“We’re the earthquake capital of the Big Ten, at least,” he said. “This is earthquake country, and Ohio is situated so that we’ve experienced more than every state around us.”
So just what is it that seems to make Ohio so … shaky?
“That’s the question everyone is interested in _ and the one we can’t answer for certain,” Hansen said.
There are, however, several theories about frequent earthquakes, including the one with the 3.1 magnitude that hit Tuesday.
Geologists say Ohio might be especially active because of a combination of a few ancient collisions.
The first was probably 800 million years ago, when land masses the size of continents came together, causing mountain ranges and fault lines.
Another factor is that movement still is going on.
“We know that North America is being gradually pushed westward,” Hansen said.
Sylvia Hayek, a seismologist with Natural Resources Canada, said the Ohio area also may be reacting to something called glacial or crustal rebound. The idea is that the Earth’s crust is still recovering or shifting from the retreat of glaciers. The weight of the glaciers depressed the crust of the Earth.
When they retreated about 12,000 years ago, they caused some instability in the Earth’s crust in Ohio, Hansen and Hayek said.
Hayek also said the drilling of gas or oil wells can’t be dismissed as a contributing factor to frequent earthquakes, even though drilling tends to go less than a mile deep, while most earthquakes happen three miles deep or more. Drilling under Lake Erie is illegal in the United States.
The epicenter of Tuesday’s quake, similar to a 3.8 magnitude quake in Portage County in early 2007, was out in Lake Erie and along a line known as the Akron Magnetic Lineament. It’s the same fault zone that spawned a 5.0-magnitude earthquake in 1986.
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