GREENBACK, TN – A light earthquake rattled East Tennessee and surrounding states early this morning, May 10, 2025. While no significant damage or injuries have been reported, the event served as a reminder of the seismic activity present in the region.
- Earthquake Details: A magnitude 4.1 earthquake centered near Greenback, East Tennessee, was widely felt across several southeastern states. No significant damage or injuries were immediately reported.
- Seismic Context: The Appalachian region, particularly the Eastern Tennessee Seismic Zone, experiences frequent small earthquakes. While most are minor, felt events occur about annually, and larger, more damaging earthquakes are possible but less common.
- Aftershock Outlook: The USGS estimates a small chance (around 5%) of a magnitude 4 or larger aftershock in the week following the main earthquake. Residents are advised to be prepared.
Details of the Earthquake
The preliminary magnitude of the earthquake was reported as 4.1 by the United States Geological Survey (USGS), which was upgraded from an initial report of 3.5. The epicenter was located approximately 13 miles from Greenback, Tennessee, which is about 30 miles south of Knoxville. The earthquake struck at around 9:04 AM Eastern Time and had a depth of about 15 miles.
The tremor was widely felt across several southeastern states due to the efficient propagation of seismic waves in the Eastern U.S.’s dense, ancient bedrock. Reports of feeling the shaking came from residents in Tennessee, Georgia (including Atlanta), North Carolina, South Carolina, Alabama, Kentucky, and Virginia. Some individuals described a gentle swaying or rattling of household items. Over 23,000 people reported feeling the earthquake to the USGS in the first hour after it occurred. Emergency responders in Knoxville reported no immediate calls related to injuries or structural damage.
Earthquake Magnitude and Frequency in the Appalachians
Earthquakes are classified by their magnitude on a logarithmic scale. Generally:
- Magnitudes below 2.5 are usually not felt.
- Magnitudes between 2.5 and 5.4 are often felt but rarely cause significant damage. The May 10th earthquake falls into this category.
- Magnitudes between 5.5 and 6.0 can cause moderate damage.
- Magnitudes between 6.1 and 6.9 can cause significant damage in populated areas.
- Magnitudes of 7.0 and higher can cause severe and widespread destruction.
The Appalachian region, particularly the Eastern Tennessee Seismic Zone (ETSZ), is one of the more seismically active areas in the eastern United States. While most earthquakes in this zone are small and only detectable by instruments, felt earthquakes occur approximately once per year. The ETSZ extends from northeastern Alabama to southwestern Virginia. Historically, the largest recorded earthquakes in this zone have been around magnitude 5.1. Scientists estimate that earthquakes as large as magnitude 7.5 are possible in the ETSZ, although events in the magnitude 5-6 range are estimated to occur every 200 to 300 years. The exact causes of the seismic activity in the ETSZ are not well understood, as the area is far from any tectonic plate boundaries, and known faults are ancient with no clear surface expression.
Aftershock Probability
The USGS has indicated that there is a small chance (around 5%) of a magnitude 4 or larger aftershock occurring in the next week following the May 10th earthquake. Aftershocks are smaller earthquakes that occur after a mainshock in the same general area. Their frequency typically decreases over time. While the possibility of a larger aftershock cannot be entirely ruled out, it is considered unlikely. Authorities advise residents to be prepared for the possibility of aftershocks by knowing what to do during an earthquake: drop, cover, and hold on if indoors, and stay clear of buildings if outdoors.
