A 4.1 magnitude earthquake in east Tennessee Saturday morning was felt in Atlanta and Charlotte, North Carolina.

The quake originated near Greenback, about 30 miles southwest of Knoxville, at 9:04 am, according to the US Geological Survey.

The USGS reported the tremor had a depth of almost 25 miles, making it a shallow earthquake, which is anything less than 43 miles below ground.

The last time a strong earthquake was felt in the region was 2018, when a 4.4 magnitude tremor rattled houses but caused little damage.

The faults in East Tennessee are inactive, but those in West Tennessee nearest the Mississippi River (New Madrid, Missouri) are perhaps active now. The locations of most major faults in East Tennessee are precisely known, and only a few of the 40 or so major faults there are drawn.

The New Madrid Seismic Zone (NMSZ) is a major fault zone in the central Mississippi Valley, stretching from Missouri to Arkansas, and known for its potential for large earthquakes, including the Great New Madrid Earthquakes of 1811-1812.

The NMSZ is the most seismically active area east of the Rocky Mountains in the United States.