On November 9, 1968, at 11:02 a.m. local time, a powerful earthquake shook the state of Illinois and several neighboring states. The quake, which had a magnitude of 5.3 on the Richter scale, was the largest ever recorded in Illinois and one of the strongest in the Midwest region. The epicenter was located near the town of Hamilton in southeastern Illinois, about 120 miles east of St. Louis, Missouri.
The quake was felt as far away as Canada, Alabama, and Georgia, and caused widespread damage and disruption to buildings, roads, bridges, power lines, and communication systems. The quake also triggered hundreds of aftershocks, some of which were felt for weeks after the main event.
The Causes and Effects of the Quake
The 1968 Hamilton County earthquake was caused by the movement of the Wabash Valley Fault System, a complex network of faults that extends from southern Illinois to southwestern Indiana. The fault system is part of the larger New Madrid Seismic Zone, which is responsible for some of the most devastating earthquakes in U.S. history, such as the 1811-1812 New Madrid earthquakes that temporarily reversed the flow of the Mississippi River. The Wabash Valley Fault System is considered to be active and capable of producing large earthquakes in the future.
The 1968 quake caused an estimated $10 million in damage (equivalent to about $75 million in 2020), mostly in Illinois, Indiana, and Kentucky. The damage was concentrated in the rural areas near the epicenter, where many buildings were poorly constructed and not designed to withstand seismic forces. Some of the most severely affected structures included schools, churches, barns, silos, and water towers.
The quake also damaged several historic landmarks, such as the Old State Capitol in Vandalia, Illinois, and the Lincoln Home National Historic Site in Springfield, Illinois. The quake also disrupted the operations of several coal mines, oil wells, and nuclear power plants in the region. Fortunately, no fatalities or serious injuries were reported, although many people experienced panic, anxiety, and stress due to the unexpected and violent shaking.
The Implications and Lessons of the Quake
The 1968 Hamilton County earthquake was a wake-up call for the state of Illinois and the Midwest region, as it demonstrated the potential for seismic hazards in an area that was previously considered to be relatively stable and safe. The quake prompted the state and federal governments to conduct extensive studies and surveys of the seismic activity and risk in the region, and to implement new regulations and standards for earthquake-resistant design and construction.
The quake also raised public awareness and preparedness for earthquakes, and encouraged the development of emergency plans and response systems. The quake also stimulated scientific research and innovation in the fields of seismology, geology, engineering, and disaster management.
The 1968 quake remains the largest and most destructive earthquake in the history of Illinois, but it may not be the last. According to the U.S. Geological Survey, there is a 25 to 40 percent chance of a magnitude 6.0 or greater earthquake occurring in the New Madrid Seismic Zone within the next 50 years, and a 7 to 10 percent chance of a magnitude 7.0 or greater earthquake.
Such a quake could cause significant damage and disruption to the densely populated and economically vital areas of the Midwest, such as Chicago, St. Louis, Memphis, and Nashville. Therefore, it is important for the residents, businesses, and authorities of Illinois and the surrounding states to be aware of the seismic threat and to take appropriate measures to reduce the risk and enhance the resilience of their communities.