Why earthquakes in the suburbs are so rare
Despite the rarity of earthquakes in Northern Illinois, Matt Lowry was certain that’s what shook his computer screen Wednesday afternoon while he was working in his home office in Mundelein.
“I had felt one years ago, a tiny one, and I immediately wondered if it was an earthquake because it felt so similar,” Lowry recalled.
His wife felt it too, and soon confirmed it was an earthquake via a quick internet search. But Lowry said he got confirmation from his cat.
“I looked in one of the rooms where one of my cats was sitting on the bed, and she was super perked up and her ears were up like, ‘What just happened, man?’” Lowry said. “She was a little bit freaked out.”
The 2.9-magnitude temblor happened at 2:38 p.m. Wednesday, about 12 miles east of Highland Park and about three miles below Lake Michigan, according to the U.S. Geological Survey.
The quake was barely strong enough to be felt. Usually anything under a magnitude of 2.5 is felt only by seismographs, according to experts.
Earthquakes are rare in Northern Illinois because of our geography, explained Suzan van der Lee, a professor of earth sciences at Northwestern University.
“We are not near a tectonic plate boundary, which is where the most seismically active fault zones are,” she said. “There are slightly more earthquakes in Southern Illinois than in Northern Illinois.”
That’s because Southern Illinois rests on two separate seismic zones — New Madrid and Wabash Valley.
The New Madrid fault line is more active, according to USGS records. It’s located along the southwestern part of the state, extending south into the Missouri boot heel and covering parts of Tennessee, Arkansas and Mississippi as well. In fact, seven quakes have been recorded along the fault line in the past three weeks, including a 1.9-magnitude shaker Friday morning about four miles below Tiptonville, Tennessee.
The Wabash Valley zone runs along the state’s southeastern border with Indiana. A 3.5-magnitude earthquake was recorded along this fault line less than two weeks ago in downstate West Salem.
According to van der Lee, earthquakes that can be felt by humans occur about once every two to three years in Northern Illinois. Besides Wednesday’s quake and the one in West Salem, the only other quake to register with an epicenter in Illinois this year was a 3.8-magnitude quake near downstate Pana in January.
The most powerful in recent memory was a 5.4-magnitude quake near downstate Mt. Carmel, along the Indiana border, in 2008. Two injuries were reported.
“Most are low- to medium-magnitude, and Illinois buildings can withstand, and have withstood, the weak to light shaking they caused,” van der Lee said.
The Illinois Emergency Management Agency offers guidance on its website for residents in the event of an earthquake. Many injuries occur when someone runs through a building during an earthquake, officials said.
Instead, people should stay away from windows, take cover under a table or sturdy furniture and don’t get in elevators. If outside, move to an open area. Pull over, if driving.