Earthquakes are a verifiable phenomenon in Arkansas, though the state is not commonly associated with high seismic risk like California. A significant portion of eastern Arkansas sits within the influence of one of the most historically powerful seismic areas in North America. This region has a geological past that includes some of the largest earthquakes ever recorded in the continental United States, meaning the possibility of future seismic activity is a recognized concern. The state’s seismic profile is defined by this powerful history and the ongoing, mostly low-level, activity monitored by scientists today.
The Primary Seismic Threat
Arkansas’s main seismic hazard originates from the New Madrid Seismic Zone (NMSZ), a vast network of faults extending roughly 150 miles southward from Missouri, through the northeastern corner of Arkansas, and into other surrounding states. The NMSZ is an intraplate earthquake zone, meaning the fault system is located in the middle of the North American Plate, unlike boundary earthquakes. The underlying geological feature responsible for this weakness is the Reelfoot Rift, an ancient, buried rift zone that failed to split the continent over 600 million years ago.
This rift left behind a deep, structural weakness in the crust. The NMSZ faults, which cannot be seen from the surface, lie within the confines of this failed rift, allowing accumulated stress from the moving tectonic plate to be periodically released as earthquakes. Furthermore, the geology of the central United States allows seismic energy to travel much farther than it would in the western U.S.
Historical Impact: The Great Earthquakes of 1811-1812
The most extreme example of this seismic potential is the New Madrid Earthquakes of 1811–1812, which included four major quakes. The first massive shock, estimated to have a moment magnitude between 7.2 and 8.2, occurred on December 16, 1811, with an epicenter in what is now northeastern Arkansas. This initial quake was followed by two others of similar magnitude in January and February 1812, making it the most powerful earthquake sequence in the recorded history of the continental United States east of the Rocky Mountains.
The geological impact was extensive, with effects felt as far away as Boston. In the epicentral area, the ground experienced widespread liquefaction, fissuring, and the formation of sand blows. The landscape was permanently altered, notably with the formation of Reelfoot Lake in Tennessee due to land subsidence and the expansion of Lake St. Francis in eastern Arkansas. Accounts describe the Mississippi River temporarily appearing to flow backward due to massive waves and riverbank collapse.
Current Seismic Activity and Monitoring
The New Madrid Seismic Zone remains active today, averaging approximately 200 small earthquakes each year, though most are too small for residents to feel. Scientists monitor this activity using a network of seismograph stations operated by the U.S. Geological Survey (USGS) and regional universities. These instruments track frequent microseismic earthquakes, which have magnitudes less than 2.0.
Based on paleoseismic studies, researchers estimate that major earthquake sequences similar to 1811–1812 have a recurrence interval of around 500 years. Current modeling suggests a 7 to 10 percent chance of a magnitude 7.5 to 8.0 earthquake occurring in the NMSZ within the next 50 years. A magnitude 6.0 or greater earthquake has a higher probability, estimated at 25 to 40 percent in the same 50-year timeframe.
Preparing for Future Seismic Events
Because a significant earthquake cannot be predicted, residents of Arkansas are encouraged to focus on preparedness and mitigation. The most immediate safety action during shaking is to follow the “Drop, Cover, and Hold On” protocol. This involves dropping to the floor, taking cover under sturdy furniture, and holding onto it until the shaking stops, protecting the head and neck.
Developing a family communication plan is recommended, including identifying an out-of-state contact, as local phone service may be disrupted. Since many buildings in the region were not constructed with modern seismic standards, securing heavy furniture, water heaters, and shelving to walls can prevent injury and damage. Emergency management officials recommend that families prepare a supply kit with enough non-perishable food, water, and essential medications to be self-sufficient for two weeks after a major event.