Ohio does experience earthquakes, though it is not situated on a major tectonic plate boundary. The state lies firmly within the North American continental interior, meaning its seismic activity is intraplate seismicity, unlike the powerful quakes seen on plate edges. While most tremors are minor and generally unfelt, Ohio’s geological past and present-day stresses occasionally produce moderate earthquakes. This activity results from deeply buried, ancient faults reacting to continuous pressure across the continent.
Documented History of Earthquakes in Ohio
Ohio’s seismic history includes over 200 recorded earthquakes of magnitude 2.0 or greater since 1776. Most of these events are small, localized tremors that cause no damage or injury. However, a few events have been powerful enough to cause minor to moderate damage.
The largest recorded event was a magnitude 5.4 earthquake that struck near Anna in Shelby County in March 1937. This tremor was felt across eight states and parts of Canada, causing significant structural damage, including the local high school being torn down. Northeastern Ohio experienced a magnitude 5.0 earthquake near Perry in Lake County in 1986. This event caused minor damage and was notable for occurring near a nuclear power plant.
The state also sees seismic swarms, such as a series of earthquakes in the Youngstown area around 2011 and more recently in Noble County. These events typically range from magnitude 3.0 to 4.0 and are generally felt only locally. While major, destructive earthquakes are rare, the historical record demonstrates the potential for moderately damaging events across different regions of the state.
Underlying Geological Causes of Midwest Seismicity
Earthquakes in Ohio and the broader central and eastern United States are classified as intraplate seismicity because they occur far from any active plate boundary. The primary cause is the slow, continuous build-up of strain within the North American continental plate. This strain results from large-scale tectonic forces, such as the westward push of the plate as the Atlantic Ocean floor spreads.
This accumulated stress is periodically released along ancient zones of weakness within the Earth’s crust. These weaknesses are deeply buried, poorly known faults located in the Precambrian basement rock, which formed over a billion years ago. When the tectonic stress becomes too great, these prehistoric faults are reactivated, causing the bedrock to slip and releasing seismic energy.
A modern development influencing local seismicity is the deep underground injection of fluids, particularly wastewater from oil and gas operations. The injection process increases pore pressure within the rock, effectively allowing dormant faults to slip more easily. This induced seismicity has been documented in various parts of the state, prompting stringent regulations on injection well operations.
Ohio’s Primary Seismic Zones
Seismic activity is concentrated in several distinct geographical regions linked to underlying fault structures. The most historically active area is the Anna Seismic Zone, located in Western Ohio near the village of Anna. This zone is associated with deep, ancient structures like the Auglaize fault and the Fort Wayne Rift, which are remnants of a failed continental rift.
Northeastern Ohio, particularly the area along the Lake Erie shore, represents another significant seismic zone. This region experienced the 1986 M5.0 event, which some geologists suggest occurred along the north-south trending Akron magnetic boundary in the basement rock. Southeastern Ohio has also recorded felt earthquakes, with a concentration of events near the Ohio River.
Although not within Ohio’s borders, the New Madrid Seismic Zone, centered in the mid-Mississippi Valley, presents a regional hazard. Ohio lies on the periphery of this major zone. The powerful New Madrid earthquakes of 1811–1812 were felt strongly enough in Cincinnati to topple chimneys, meaning the state’s western and southern regions are subject to shaking from large events originating elsewhere.
Assessing Risk and Safety Measures
The overall risk of a major, destructive earthquake in Ohio is low compared to active plate boundaries, but the potential for moderate damage remains. A significant factor amplifying this risk is the presence of thick, unconsolidated glacial sediments across much of the state. These soft deposits can magnify seismic waves, causing more intense ground shaking than areas built directly on solid bedrock.
This localized amplification means that even a moderate earthquake can cause disproportionate damage in areas with deep sediment fill, such as the ancient Teays River Valley beneath the Anna Seismic Zone. Ohio building codes account for this low-to-moderate risk by assigning seismic design categories to various regions. For construction in higher-risk categories, the Ohio Building Code requires a geotechnical investigation to evaluate potential hazards like liquefaction and ground displacement.
In the event of an earthquake, residents should follow the standard “Drop, Cover, and Hold On” procedure. This involves immediately dropping to the ground, taking cover under sturdy furniture, and holding on until the shaking stops. Preparedness involves knowing where to seek shelter and understanding that ground motion can travel great distances in the eastern United States.