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TENNESSEE QUAKES OF NOTE

› Aug. 17, 1865: A magnitude-5.0 quake occurred outside of Memphis, near New Madrid, Missouri. The quake knocked down chimneys in Memphis and sent large waves through the Mississippi River. The shocks were felt through Missouri, Tennessee, Mississippi and Illinois.

› 1811-1812: Three New Madrid earthquakes rocked up to 3.1 million square miles across Kentucky, Missouri and Tennessee — raising and sinking land masses and creating fissures over 80,000 square miles. The greatest of those tremors registered greater than 7.0 magnitude and created Reelfoot Lake in Northwest Tennessee.

› Jan. 4, 1843: Severe earthquakes in Memphis registered an VIII intensity and up to 6.9 magnitude. The shocks were felt sharply in Nashville and as far away as Knoxville, although no significant damage was done in those cities.

› March 28, 1913: Earthquakes centered in Knoxville cracked walls and toppled chimneys across 4,300 square miles in East Tennessee. The shocks were rated up to 5.9 magnitude.

› Oct. 30, 1973: Cracks in the walls were reported at the University of Tennessee Medical Center in Knoxville after a 4.6 magnitude earthquake south of Knoxville sent rumbles throughout the region. Minor damage to walls, windows and chimneys occurred in Blount County.

Source: U.S. Geological Survey

December 2018 was a banner month for earthquakes in Tennessee.

U.S. Geological Survey records show East Tennessee was rattled by at least seven magnitude-2.5 or greater earthquakes in December, the strongest of them a magnitude 4.4 north of Decatur near the Watts Bar Nuclear Plant.

In fact, Tennessee was home to seven of the eight magnitude-2.5 or stronger quakes recorded east of the Mississippi River in December. The non-Tennessee temblor, a magnitude 2.5, struck Dec. 9 about 325 miles northwest of Decatur near Pickneyville, Illinois, southeast of St. Louis, USGS records show.

Due to the federal government's shutdown, USGS officials were unavailable Monday to discuss data on the quakes, but most earthquake records remain up to date. USGS data from 2014 shows an increased hazard in Southeast Tennessee since the last study in 2008.

Tennessee regularly has smaller earthquakes but the magnitude-4.4 quake that struck just a few miles east of Watts Bar Nuclear Plant at 4:14 a.m. on Dec. 12 was the strongest in nearly a half-century. Forty-five years ago, an earthquake that struck near Maryville was slightly stronger at magnitude 4.7, according to the National Weather Service.

The Meigs County quake was centered a few hundred yards behind the home of Bill and Judy Emerson, who told the Times Free Press they were awakened by noise and vibration that shook open cabinet doors and rattled doors and windows.

Earthquakes less than magnitude 3.0 usually can't be felt, but people felt the magnitude-4.4 quake as far away as Chattanooga, Nashville, Knoxville and even Atlanta, according to USGS data.

It was followed less than 15 minutes later by a 3.0-magnitude temblor, which was about a mile closer to the Tennessee Valley Authority facility.

Those first two Meigs quakes were followed the next afternoon by a magnitude-2.5 quake centered about halfway between them.

But that wasn't all the shaking in East Tennessee for December.

On Dec. 8, a magnitude-2.7 quake hit about 7.5 miles northwest of Sweetwater in Monroe County. It was 13.5 miles deep, USGS records show.

On Dec. 13, a magnitude-2.6 quake struck about 3 miles deep near the town of Blaine, about 20 miles northeast of Knoxville.

Not far away from Blaine on Dec. 15, a magnitude-3.0 quake occurred more than 12 miles deep near the community of Mascot, about 14 miles northeast of Knoxville.

And the seventh December quake in Tennessee struck almost 12 miles deep the afternoon of the 23rd about 8 miles southeast of the town of Vonore.

Little or no damage was reported in any of the temblors.

December's quakes in Meigs County occurred near an operating nuclear plant, which got federal attention focused on shaky Meigs for a few days.

The Dec. 12 quake triggered warning lights that notified TVA operators on duty at Watts Bar that there had been an abnormal operating procedure, water in refueling tanks had shifted, and instruments on the turbine had detected ground vibration, TVA officials told the Times Free Press during a training session they held for the public a week afterward.

There was no damage and the facility never stopped operating, but in the days that followed TVA sought to address public concerns by demonstrating what response looks like when an earthquake strikes.

"This whole plant is designed with a seismic event in mind," Sequoyah Nuclear Plant operation superintendent Kevin Michael said during a Dec. 19 demonstration at Sequoyah Nuclear Plant in Soddy-Daisy.

Engineers who designed and built the facility looked at the most severe disasters dating back centuries, then implemented designs to withstand them, officials said. Emergency plans were put in place for each scenario, and others were added in case a never-before-seen disaster struck East Tennessee.

The largest earthquake in Tennessee history was a magnitude 5.0 temblor outside of Memphis in August 1865 that was so strong it produced large waves on the Mississippi River.

Contact staff writer Ben Benton at bbenton@timesfreepress.com or 423-757-6569. Follow him on Twitter @BenBenton or at www.facebook.com/benbenton1.

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