The 1968 Illinois earthquake was one of the most widely felt seismic events in U.S. history, affecting 23 states across 580,000 square miles.
Key Facts
- Richter Magnitude
- 5.3
- Date and Time
- November 9, 1968, 11:02 a.m.
- Area Affected
- 580,000 sq mi across 23 states
- Fatalities
- None
- Scientific Discovery
- Cottage Grove Fault identified in Southern Illinois Basin
- Future Risk Estimate (2005)
- 90% chance of magnitude 6–7 tremor before 2055
By the Numbers
Location
Cause → Event → Consequence
The earthquake originated as a New Madrid seismic zone event within the Southern Illinois Basin. Tectonic stresses along deep fault structures in the central United States, including the previously unknown Cottage Grove Fault, were responsible for the rupture. The region sits atop one of North America's most active intraplate seismic zones.
On November 9, 1968, at 11:02 a.m., a magnitude 5.3 earthquake struck Illinois, making it the largest recorded earthquake in state history. Millions of people felt the shaking, which toppled chimneys and caused structural damage to buildings. The tremor was perceptible as far away as Chicago and across 23 states, covering roughly 580,000 square miles.
No fatalities resulted, though structural damage was widespread. The event prompted scientific investigation that led to the discovery of the Cottage Grove Fault. Subsequent studies raised awareness of future seismic risk in the region; by 2005, experts estimated a 90% probability of a magnitude 6–7 earthquake occurring before 2055 along the Wabash Valley or New Madrid fault zones.
Human Cost
Each dot represents approximately 10,000 deaths. Total estimated: 0 (earthquake)