Curious Iowa: Are earthquakes possible in Iowa?

Earthquakes in Iowa rare, but it’s not impossible for Iowans to feel the shake of an earthquake.

But how possible is it for Iowa to experience an earthquake?

That’s what one person wrote to ask The Gazette’s Curious Iowa, a series that answers readers’ questions about Iowa history, it’s people and the culture.

What is the risk for earthquakes in Iowa?

Igor Beresnev, a professor of geophysics and seismology in the Department of Geological and Atmospheric Sciences at Iowa State University, said Iowa is among the U.S. states that are least likely to experience an earthquake.

According to the U.S. Geological Survey’s seismic hazard map, Iowa, Minnesota, Wisconsin, Michigan, North Dakota and parts of Texas and Florida are at the lowest risk of having an earthquake.

Areas of the country that are shaded with reds, oranges and yellows on the map are indicators of regions with higher earthquake risks. Much of the west coast, the edges of Missouri, Kentucky, Tennessee and Arkansas, along with portions of Hawaii and Alaska are the most likely to experience an earthquake.

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Ryan Clark, associate state geologist with the Iowa Geological Survey, said fewer than a dozen earthquakes with epicenters in Iowa have occurred over the past 150 years.

“Iowa is in one of the most seismically quiet regions of the U.S.,” Clark said.

While they are rare, earthquakes are possible in Iowa because of several fault systems throughout the state, however none of them are considered active, Clark said.

A tectonic fault is a fracture in the Earth's rocky crust where blocks of rock move past each other due to built-up stress, often resulting in rapid slips that cause earthquakes.

One of the most active tectonic faults in the U.S. is the San Andreas Fault, in Southern California.

How often do earthquakes occur in Iowa?

Earthquakes in other states have been strong enough to be felt by Iowans. Beresnev said this has happened in recent years, with earthquakes in Illinois and Oklahoma.

In 2016, an earthquake in northern Oklahoma was felt in Des Moines, about 400 miles from the epicenter of the 5.6-magnitude quake in Pawnee.

In 2010, a small earthquake in northern Illinois startled people as far away as Michigan and Iowa. The epicenter of the 3.8-magnitude earthquake was about 45 miles northwest of Chicago.

And more recently, in 2023, a magnitude 3.6 earthquake rattled parts of northern Illinois, awakening some residents and spurring reports to 911 about homes shaking. The quake was centered about 100 miles southwest of downtown Chicago.

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“The probability of the living generations of Iowans experiencing damaging ground motions is near zero,” Beresnev said. “This is all explained by the Iowa geology: the state is situated on a very old, tectonically stable continental crust with little internal deformation, far away from active tectonic faults and plate boundaries.”

Clark said the feeling of an earthquake can be subjective.

“Iowans feel shaking quite often, however it is usually due to trucks, trains or even blasting at a nearby quarry,” Clark said. “Feeling an actual earthquake in Iowa is quite rare, perhaps less than once per year.”

However, Clark said the greater the magnitude — which refers to the measurement of the size of an earthquake based on total energy released by the quake — of the earthquake corresponds to the distance it can be felt.

“It really depends on the proximity and magnitude of an earthquake whether it is felt in Iowa or not,” he said.

Could Iowa’s risk for earthquakes change?

Although Iowa’s current earthquake risk and projections are low, Clark said it could change in the future, adding that “given enough time, anything is possible.”

“During our lifetime the tectonic stress regime is not likely to change enough to cause activation of Iowa’s faults,” Clark said.

He added that seismic activity in Iowa could increase through “induced seismicity,” which happens when substances are injected deep underground.

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Clark said hydraulic fracturing — commonly known as “fracking” — is an example of this. Fracking is the process of injecting fluids deep underground at high pressures to fracture rock layers so resources like petroleum or natural gas can be extracted.

“There is no fracking going on in Iowa currently (but) if new industries develop in Iowa that require deep underground injection, then induced seismicity could become a new hazard that would need to be monitored,” Clark said.

Clark said the IGS, which is housed within the University of Iowa, does not have the resources to monitor seismic activity or adequately assess seismic hazards in Iowa.

However, a few years ago the IGS conducted a study to evaluate the potential for induced seismicity related to an underground natural gas storage facility in central Iowa.

Future drilling also is possible as companies have begun exploring whether geological hydrogen exists underground in Iowa. The U.S. Geological Survey recently flagged several zones across the country as having a higher potential for hydrogen deep under the Earth’s surface.

Iowa is one of several states that have some areas with high potential for geologic hydrogen. That’s because of a geologic rift -- the Midcontinent Rift system -- running through the state.

Clark told The Gazette earlier this year that the Iowa Geological Survey has been contacted by “a fair amount” of companies — both U.S. and abroad — that are interested in finding geologic hydrogen sources in Iowa.

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Olivia Cohen covers energy and environment for The Gazette and is a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues. She is also a contributing writer for the Ag and Water Desk, an independent journalism collaborative focusing on the Mississippi River Basin.

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Comments: olivia.cohen@thegazette.com