Orange dot represents epicenter of the earthquake that struck July 15, 2024. (U.S. Geological Survey)
Residents of small towns roughly 60 miles west of Chicago woke up Monday to what they thought was thunder, but turned out to be an earthquake.
The 3.4 magnitude tremor struck just before 3 a.m., with an epicenter near Somonauk, Ill., according to the U.S. Geological Survey.
“Low rolling rumble ... then the house shook,” one resident reported, commenting on a Facebook post shared by the DeKalb County Sheriff’s Office.
Those nearest to a small earthquake will feel a sharp jolt, followed by stronger sharp shakes that pass quickly, USGS said. Damage typically doesn’t occur until quake magnitude hits above 4 or 5.
While earthquakes are rare east of the Rocky Mountains, Illinois sits within two “hot spots” for quakes in the central U.S., and has experienced three in the past 12 months, including two in late 2023.
One hot spot is the New Madrid Seismic Zone, which spans the central Mississippi Valley from Cairo, Ill., through southeastern Missouri, western Kentucky, western Tennessee and northeast Arkansas. This area has been the site of some of the largest earthquakes in North America, according to the state of Illinois.
Between 1811 and 1812, four catastrophic earthquakes with magnitude estimates greater than 7.0 occurred in this zone during a three-month period, with aftershocks continuing for years.
The other hot spot is the Wabash Valley Seismic Zone in southeastern Illinois and southwestern Indiana. The epicenter of this zone is located between Mt. Vernon, Ill., and West Franklin, Ind. Geologists have found evidence of prehistoric earthquakes in this region.
Few earthquakes in the region can be linked to named faults, with numerous smaller or deeply buried faults remaining undetected by scientists, USGS said.
According to USGS, earthquakes east of the Rocky Mountains are typically felt over a much broader area than earthquakes of similar magnitude in the west. A magnitude 4.0 earthquake in eastern or central North America could be felt in communities more than 60 miles from its source, USGS said.
Contact Patty Wetli: @pattywetli | (773) 509-5623 | [email protected]
