1973 Knoxville earthquake
On November 30, 1973, at 02:48 a.m. EST (07:48 UTC), a magnitude about 4.7 earthquake struck about 1 kilometer northeast of Alcoa, Tennessee. The quake happened at a shallow depth of about 3 kilometers (2 miles) and was felt over a large area, about 65,000 square kilometers (25,000 square miles). The strongest shaking reached level VI (Strong) on the Modified Mercalli intensity scale.
This was the most powerful earthquake recorded in the Eastern Tennessee seismic zone, a mid-continent intraplate area far from the edge of the North American Plate. The zone contains ancient faults that generally do not reach the surface. In 2010, scientists linked this zone to the New York–Alabama Lineament and suggested earthquakes originate at depth in metamorphic rocks like gneiss.
USGS puts the main shock at moment magnitude about 4.6–4.7 with a focal depth of about 3 km. There was a foreshock of magnitude 3.4 about a month earlier, and more than 30 aftershocks followed the main event.
The earthquake’s fault movement was mainly dip-slip. With limited data, the exact motion direction is hard to pin down, but a northwest-striking reverse fault is considered the most likely cause. Intensity data show the felt area decreasing quickly to the north, with unusually slow decrease to the south, possibly due to energy focusing by local terrain, especially around Maryville.
This page was last edited on 3 February 2026, at 16:01 (CET).