SPRINGFIELD, IL – Illinois, an unlikely location for earthquakes, faces a significant seismic threat as it sits on two active seismic zones. The New Madrid Seismic Zone (NMSZ) and the Wabash Valley Seismic Zone (WVSZ) pose risks to the state. The NMSZ, which stretches across several states, including Illinois, is home to the most powerful earthquakes recorded in the continental United States.
The Illinois Emergency Management Agency (IEMA) warns that if the series of earthquakes that occurred in the winter of 1811-12 were to happen today, the estimated damage would range between $60 to $80 billion. Although over 3,000 earthquakes have been recorded in the NMSZ since 1974, none have exceeded a magnitude of 5.0.
Director Alicia Tate-Nadeau recently emphasizes the importance of understanding the risks and being prepared for a significant earthquake. In the event of an earthquake, IEMA advises taking cover under a sturdy piece of furniture and holding on until the shaking stops. Homeowners are also encouraged to consider earthquake insurance, as standard policies generally do not cover earthquake damage. According to the Illinois Department of Insurance, homeowners can purchase earthquake coverage as an endorsement to their existing policy, with costs varying based on factors such as location and risk.
The NMSZ impacts major cities including Memphis, St. Louis, Little Rock, and Evansville. Despite its relatively lower profile compared to fault zones in California or Alaska, the NMSZ is the most active seismic area in the United States east of the Rocky Mountains. It experiences hundreds of small earthquakes annually, though most go unnoticed by the general population.
Understanding the geological complexities of the NMSZ poses challenges due to its buried faults beneath layers of alluvium. Unlike areas with visible fault lines, studying the NMSZ requires sophisticated techniques. Scientists have used paleoseismology to analyze evidence of past earthquakes preserved in soil and rock.
While the recurrence interval of moderate to large earthquakes in the NMSZ is difficult to predict, experts estimate a 10% probability of a magnitude 7.0-8.0 earthquake occurring within the next 50 years. The geographic impact of such an earthquake would be substantial, affecting areas up the Mississippi River valley to St. Louis, up the Ohio and Wabash river valleys, and down the Mississippi River valley.
Despite the infrequency of large earthquakes in the Midwest, the potential for significant damage to man-made structures remains a concern. Tall structures, large open structures, and brittle structures are particularly susceptible to damage during earthquakes.
Illinois residents are urged to stay informed about earthquake risks, prepare emergency plans, and consider earthquake insurance to mitigate potential damages. While the Midwest may not be commonly associated with earthquakes, the threat looms large, and readiness is crucial to ensure the safety and resilience of affected communities.