East Tennessee earthquake shows our fault lines. Experts say a far bigger one is possible

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12-05-2025

The East Tennessee earthquake on May 10 was one of the strongest to hit the region since 1900. The East Tennessee Seismic Zone is an active one, even if it isn't known to produce quakes strong enough to be catastrophic.
The most recent one centered near Greenback fits that pattern: At 4.1 magnitude, it wasn't enough to do damage, but it definitely was enough to catch everyone's attention.
'You guys are in earthquake country, you're in tornado country. And we always tell people when they feel an earthquake, think of that as a wake-up call,' U.S. Geological Survey geophysicist Thomas Pratt told Knox News last year.
'Given the amount of seismicity out there, you wouldn't be surprised, at any time, that you get a magnitude 4 to 5 earthquake,' he added.
A magnitude 4 earthquake can often be felt 60 miles from where it occurred. Moderate quakes begin with magnitude 5.
The East Tennessee Seismic Zone extends across Tennessee, northwestern Georgia and into northeastern Alabama. The area is not known to have major earthquake, but hundreds of earthquakes too small to be felt have been recorded in recent decades.
A 4.7 magnitude tremor shook Alcoa in November 1973, and a magnitude 4.4 magnitude occurred in Decatur, Tennessee back in 2018.
4.7 magnitude – Alcoa (1973)
4.5 magnitude – Greenville (1928)
4.4 magnitude – Decatur (2018)
4.2 magnitude – Vonore (1987)
4.1 magnitude – Luttrell (1913)
4.1 magnitude – New Tazewell (1956)
3.8 magnitude – Tazewell (1997)
3.8 magnitude – Fincastle (2020)
3.7 magnitude – Ducktown (1979)
3.7 magnitude – Tellico Plains (1995)
Tennessee is in two seismic zones: the East Tennessee zone and the New Madrid zone.
There were 177 earthquakes in Tennessee in 2024, according to USGS data. Ten of those were 2.5 magnitude or higher.
The numbers shift over time. There were 301 Tennessee earthquakes in 2018 but just 11 in 1994.
The ground shakes when there is a sudden slip on a fault. The sudden slip releases energy in waves that travel through the earth's crust, according to USGS.
Some fault systems, like San Andreas in California, have been well-studied and can help determine what specific fault caused an earthquake. But that's not the case in East Tennessee.
'(The East Tennessee Seismic Zone is) a seismic zone we know the least about … and yet it's one of the largest ones in the Eastern U.S.,' Pratt said. 'So, it's a concern because it's long enough that it could have a pretty good size earthquake on it if the whole thing ruptures.'
Earthquakes in East Tennessee often occur so far underground (as far as 20 miles deep in recent cases) that it's extremely difficult to study the fault system and determine patterns. Some of the recorded quakes don't reach the surface.
'The best guide to earthquake hazards in (this specific) seismic zone is the earthquakes themselves,' USGS stated in a summary of the 2018 Decatur tremor.
Pratt also noted that faults tend to be in valleys where rocks erode more easily. But when the Tennessee Valley Authority intentionally flooded parts of the valley in the early 20th century, that made it difficult to study those areas.
'So it could be that there's evidence for earthquakes down in some of those valleys, but they were flooded in the 1930s and '40s and so we will never know,' Pratt said.
Earthquakes in the Eastern U.S. can be felt at greater distances than those that occur in the west, USGS states. The Decatur quake was felt over a 310-mile span.
Although the East Tennessee Seismic Zone is very active, our region is not known to have earthquakes that cause significant destruction. The region has been steady and stable, Pratt said. Largely unfelt tremors regularly occur and quakes in the magnitude 4 range happen once or twice a year.
Pratt did say, however, magnitude 6 quakes are possible in Eastern states, but they typically occur only once every 2,000 to 3,000 years.
Pratt advises people to stock up on emergency supplies. Recommended supplies include water for several days, nonperishable food, flashlights, a battery-powered radio, first aid kit and a whistle to signal for help, according to the Tennessee Emergency Management Agency.
Other tips for earthquake preparedness include securing items that could topple over or fall, having an emergency plan and a place to meet if your family is separated and considering an earthquake insurance policy, which can lessen financial burdens in the aftermath of an earthquake.
Traditional homeowners and business insurance policies do not cover earthquake damage, according to the Tennessee Department of Commerce and Insurance. But earthquake insurance is available to purchase in Tennessee from licensed insurance producers.
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Devarrick Turner is a trending news reporter. Email [e-mail]. On X, formerly known as Twitter @dturner1208.
This article originally appeared on Knoxville News Sentinel: East Tennessee earthquake: what is the seismic zone? Is a big one coming?