1865 Memphis earthquake
The 1865 Memphis earthquake struck southwest Tennessee on August 17, 1865. Soon after the magnitude 5.0 earthquake hit, land appeared to roll and waves formed in nearby rivers. The force of the earthquake felled and cracked chimneys in Memphis and New Madrid. Shaking of the earthquake spread as far as St. Louis, Jackson, and Illinois. It is to this day the most powerful known earthquake in the history of the state.
The earliest earthquakes known to have stricken Tennessee did so in 1811 and 1812, when the New Madrid Earthquakes rocked the Midwestern United States. Damage consisted of fallen chimneys and major geologic changes, including sand volcanoes, fissures, and even sinking of land. Thereafter, three major events (in 1843, 1865, and 1895) occurred within the state. The 1843 event registered Mercalli scale intensities of VIII, cracking walls, shattering windows, and toppling chimneys. Felt over an area of 1,000,000 square kilometers (386,102 sq mi), it caused more alarm than damage in Western Tennessee.
Having begun at 15:00 UTC, the 1865 temblor has been labeled by the USGS as the "Largest Earthquake in Tennessee". The thrust of the earthquake felled chimneys in Memphis, and the earth "appeared to undulate", creating small waves on rivers nearby. The earthquake was felt from Illinois to Mississippi; according to the United States Geological Survey, it had a Mercalli scale intensity of VII and a Richter scale magnitude of 5.0.
Nevertheless, in another report on Tennessee earthquakes, "Tennessee Earthquake History", the USGS fails to mention the 1865 earthquake and assigns to the 1843 temblor a greater Mercalli scale intensity of VIII.