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Introduction
Early Monday morning, a 3.4 magnitude earthquake shook the small town of Somonauk, Illinois, located in DeKalb County. This seismic event, confirmed by the United States Geological Survey (USGS), was felt by residents in various parts of the western suburbs of Chicago, including Yorkville and Oswego. Although there were no reported damages, the tremor served as a reminder of Illinois’ vulnerability to seismic activities.
Illinois is not commonly associated with earthquakes, but the state is situated near two significant seismic zones: the Wabash Valley Seismic Zone and the New Madrid Seismic Zone. These zones have a history of producing substantial earthquakes, affecting not only Illinois but also several other states in the region.
Details of the Somonauk Earthquake
The Event
On Monday at approximately 2:53 a.m., a 3.4 magnitude earthquake struck about 2 kilometers northwest of Somonauk. The DeKalb County Sheriff’s Office quickly took to Facebook to inform residents who were awakened by the shaking. Despite the quake’s moderate strength, no damage reports have surfaced, but the tremor was felt in nearby areas, including Yorkville and Oswego.
Location and Impact
Somonauk, a small town in DeKalb County, is situated around 35 miles west of Aurora, Illinois. The earthquake’s epicenter was in a relatively quiet seismic area, making this event particularly noteworthy. The Illinois Emergency Management Agency and Office of Homeland Security have indicated that Illinois is at risk from two major seismic zones, highlighting the state’s susceptibility to future quakes.
Seismic Zones in Illinois
Wabash Valley and New Madrid Seismic Zones
- Wabash Valley Seismic Zone: Located between southeastern Illinois and southwestern Indiana.
- New Madrid Seismic Zone (NMSZ): Situated in the Central Mississippi Valley, covering parts of Alabama, Arkansas, Illinois, Indiana, Kentucky, Missouri, Mississippi, and Tennessee.
According to the Illinois Emergency Management Agency, there’s a 25% to 40% chance of a magnitude 6.0 or greater earthquake occurring in these zones within any 50-year period.
Historical Earthquakes in Illinois
Southern Illinois and the New Madrid Fault Line
Most earthquakes in Illinois occur in the southern part of the state near the New Madrid fault line. This fault system has produced some of the most powerful earthquakes in U.S. history, including events strong enough to temporarily reverse the flow of the Mississippi River and generate tremors felt as far away as Washington, D.C.
Northern Illinois Fault Systems
Contrary to popular belief, northern Illinois also has fault systems. The Sandwich Fault Zone, running from DeKalb to Dixon, and the Peru Monocline, extending southeast from Dixon across LaSalle County, are notable examples. Additionally, the Des Plaines Fault Zone north of Chicago has been identified, although it has not been associated with significant seismic activity.
Frequency and Recent Earthquakes
Earthquake Statistics
Illinois experiences an average of five earthquakes per year, but most are too minor to be felt. However, the state has seen some notable seismic events:
- March 2023: A 2.8 magnitude earthquake detected near Germantown in Clinton County.
- 2023: Two significant quakes—a 3.2 magnitude in Southern Illinois and a 3.6 magnitude in Northern Illinois.
- November 15, 2023: A 3.6 magnitude earthquake in Standard, Illinois, the strongest in northern Illinois in years.
Residents from Ottawa, Streator, Pontiac, Springfield, Aurora, and DeKalb County reported feeling the impact of the November quake.
Historical Records
The strongest earthquake in northern Illinois was a 5.1 magnitude event near Lockport in May 1909. Will County has only recorded one significant earthquake, highlighting the rarity of such events in the area. Overall, only eight earthquakes have been documented in the Chicago area since 1909.
Major Earthquakes in Illinois
- May 26, 1909: 5.1 magnitude near Lockport (Will County).
- January 2, 1912: 4.5 magnitude near Lisbon (Kendall County).
- September 9, 1985: 3.0 magnitude near Lombard (DuPage County).
- February 10, 2010: 3.8 magnitude near Lily Lake (Kane County).
- January 31, 2012: 2.3 magnitude near Lakemoor (Lake and McHenry Counties).
- June 10, 2013: 2.6 magnitude near Virgil (Kane County).
- November 4, 2013: 3.2 magnitude near Lyons (Cook County).
- March 25, 2015: 2.9 magnitude near Lake in the Hills (McHenry County).
The most powerful earthquake ever recorded in Illinois was a 5.3 magnitude quake near Norris City in November 1968, located in the southeastern part of the state.
FAQs
What are the major seismic zones in Illinois?
Illinois is at risk from two major seismic zones: the Wabash Valley Seismic Zone and the New Madrid Seismic Zone.
How often do earthquakes occur in Illinois?
Illinois experiences an average of five earthquakes per year, but most are too minor to be felt.
Where was the strongest earthquake in northern Illinois?
The strongest earthquake in northern Illinois was a 5.1 magnitude event near Lockport in May 1909.
What was the magnitude of the recent earthquake near Somonauk, Illinois?
The recent earthquake near Somonauk, Illinois, had a magnitude of 3.4.
Are there fault lines in northern Illinois?
Yes, northern Illinois has fault systems, including the Sandwich Fault Zone and the Peru Monocline.
Conclusion
While Illinois may not be the first state that comes to mind when thinking about earthquakes, it has a rich history of seismic activity, particularly in its southern regions. The recent 3.4 magnitude earthquake near Somonauk serves as a reminder of the state’s vulnerability. With fault lines running through both northern and southern Illinois, residents should remain informed and prepared for potential seismic events. Understanding the state’s seismic history and risk zones can help communities better prepare for future earthquakes, ensuring safety and resilience.