A 3.4 magnitude earthquake Monday morning struck near Somonauk, Illinois, a small town in DeKalb County, according to the United States Geological Survey.
"Information for those who were woken up a short time ago to your house shaking, there was just a 3.4 magnitude earthquake northwest of Somonauk," the DeKalb County Sheriff's Office posted to Facebook at 3:14 a.m.
According to the USGS, the earthquake struck about 2 kilometers northwest of Somonauk around 2:53 a.m. Monday. While no reports of damage occurred, some parts of the Chicago area in the western suburbs may have felt the quake, including Yorkville and Oswego.
Somonauk, in DeKalb County, is approximately 35 miles west of Aurora.
Is Illinois on a fault line?
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The Illinois Emergency Management Agency and Office of Homeland Security says Illinois is "at risk from two major seismic zones," which include the Wabash Valley Seismic Zone and the New Madrid Seismic Zone.
"The Wabash Valley Zone is located between southeastern Illinois and southwestern Indiana," the office said. "The NMSZ is located in the Central Mississippi Valley and includes portions of the states of Alabama, Arkansas, Illinois, Indiana, Kentucky, Missouri, Mississippi, and Tennessee. During any 50-year time span, there is a 25% to 40% chance of a magnitude 6.0 or greater earthquake in this seismic zone."
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Most of Illinois’ earthquakes occur in the southern half of the state near the famed New Madrid fault line. That fault system has caused some of the strongest earthquakes in United States history, temporarily reversing the flow of the Mississippi River and causing tremors that were felt as far away as Washington, D.C.
Contrary to popular belief, there are fault systems in northern Illinois as well, including the ‘Sandwich Fault Zone’ running from DeKalb to Dixon, according to the USGS.
Another fault known as the Peru Monocline runs southeast from Dixon and across the western portions of LaSalle County.
There is a fault zone north of Chicago in an area known as the “Des Plaines Fault Zone,” but that area has not caused significant seismic activity.
When was Illinois' last earthquake?
On average, Illinois gets five earthquakes per year, but we don't typically feel them, experts say.
In March, Illinois saw a 2.8 magnitude earthquake, the USGS said. It was detected just north of Germantown, Ill., a small community located in Clinton County, part of the Metro East region outside of St. Louis.
In 2023, the state saw two earthquakes, according to officials: one was a "light," 3.2 magnitude earthquake in Southern Illinois. The other was 3.6 magnitude quake, which ranked as the strongest Northern Illinois had seen in years.
When was Illinois' strongest earthquake?
Nov. 15, 2023, the USGS reported a 3.6 magnitude earthquake occurred at 4:42 a.m. Wednesday with an epicenter in Standard, Ill.
Standard in Putnam County, is approximately 100 miles southwest of Chicago.
According to a USGS map of the quake, residents in Ottawa, Streator, Pontiac and Springfield may have felt the impact. Additionally, some in Aurora and DeKalb County also reported feeling the impact, the USGS said.
It turned out to be the strongest earthquake northern Illinois had seen in years.
The title for the strongest earthquake in the northern part of the state belongs to Lockport, which recorded a magnitude-5.1 quake in May 1909.
According to the USGS, that earthquake is the only one ever recorded in Will County.
In all, only eight earthquakes have ever been recorded in the Chicago area:
May 26, 1909: 5.1-magnitude quake 3 kilometers west of Lockport. (Will County)
Jan. 2, 1912: 4.5-magnitude quake 2 kilometers west of Lisbon. (Kendall County)
Sept. 9, 1985: 3.0-magnitude quake 3 kilometers south of Lombard. (DuPage County)
Feb. 10, 2010: 3.8-magnitude quake 2 kilometers northwest of Lily Lake (Kane County)
Jan. 31, 2012: 2.3-magnitude quake 1 kilometer southwest of Lakemoor. (Lake, McHenry)
June 10, 2013: 2.6-mangitude quake 4 kilometers northeast of Virgil. (Kane County)
Nov. 4, 2013: 3.2-magnitude quake 1 kilometer south of Lyons. (Cook County)
March 25, 2015: 2.9-magnitude quake 3 kilometers west-northwest of Lake in the Hills. (McHenry County)
The strongest earthquake ever recorded that was centered in Illinois occurred in Nov. 1968, when a 5.3-magnitude quake was recorded near Norris City, in the southeastern part of the state.
