3.6 magnitude earthquake shakes Missouri’s boot-heel

MEMPHIS, Tenn. —  Residents in West Tennessee were jolted from their sleep this morning after a 3.6 magnitude earthquake hit Wednesday morning.

Several viewers from Tipton, Lauderdale and Dyers counties called in to tell WREG that they felt the earthquake around 6 a.m. Each of them had a similar story, saying they heard a noise that one person described as a “freight train” and they were jolted by the tremors.

During a phone interview, Kelly Sebastian told WREG that she and her husband were in their Newbern home when they heard a roar-like sound and then everything began shaking. She said she’s felt earthquakes before, but nothing of this magnitude.

WREG also spoke with Dyer County Sheriff Jeff Box who said the same thing. He said he has experienced other earthquakes before, but nothing quite like this. It was “pretty strong” but said so far they haven’t had any reports of damage in the area.

According to the National Weather Service, the earthquake was strong enough that it was felt as far east as Jackson, Tennessee and in parts of Kentucky.

Earthquakes in the New Madrid Seismic Zone

This map shows earthquakes (circles) of the New Madrid and Wabash Valley seismic zones (orange patches). Red circles indicate earthquakes that occurred from 1974 to 2002 with magnitudes larger than 2.5 located using modern instruments (University of Memphis). Green circles denote earthquakes that occurred prior to 1974 (USGS Professional Paper 1527). Larger earthquakes are represented by larger circles.

The New Madrid seismic zone of southeast Missouri and adjacent States is the most seismically active in North America east of the Rockies. During the winter of 1811-1812 three very large earthquakes devastated the area and were felt throughout most of the Nation. They occurred a few weeks apart on December 16, January 23, and February 7. Hundreds of aftershocks, some severely damaging by themselves, continued for years. Prehistoric earthquakes similar in size to those of 1811-1812 occurred in the middle 1400’s and around 900 A.D. Strong, damaging earthquakes struck the southwestern end of the seismic zone near Marked Tree, Arkansas in 1843 (magnitude 6.3), and the northeastern end near Charleston, Missouri in 1895 (magnitude 6.6). Since 1900, moderately damaging earthquakes have struck the seismic zone every few decades. About twice a year people feel still smaller earthquakes that do not cause damage.

Earthquakes in the central and eastern U.S. are typically felt over a much broader region than in the western U.S. East of the Rockies, an earthquake can be felt over an area as much as ten times larger than a similar magnitude earthquake on the west coast. A magnitude 4.0 eastern U.S. earthquake typically can be felt at many places as far as 100 km (60 mi) from where it occurred, and it infrequently causes damage near its source. A magnitude 5.5 eastern U.S. earthquake usually can be felt as far as 500 km (300 mi) from where it occurred, and sometimes causes damage as far away as 40 km (25 mi).

Faults

Earthquakes everywhere occur on faults within bedrock, usually miles deep. The earthquakes of the New Madrid seismic zone occur within a large network of faults called the Reelfoot rift. The rift formed about 500 million years ago, when this region was stretched in the northwest-southeast direction. Along a northeast-southwest zone at least 70 km (40 mi) wide and 500 km (300 mi) long, the rocks in the rift were slowly dropped down about 1-2 km (1 mi) along some of the faults. Now the region is undergoing east- west shortening, and the ancient faults of the Reelfoot rift are being reactivated to generate earthquakes. Today the Reelfoot rift and the New Madrid seismic zone are 2,000 km (1,200 mi) from the nearest plate boundary, which is in the Caribbean Sea.

The network of faults in the seismic zone is buried beneath hundreds to thousands of feet of sand and mud. Four of the largest faults are recognized as alignments of abundant small earthquakes, and movements along two of these faults dammed rivers and created lakes during the earthquakes of 1811-1812. A few more deeply buried faults were detected during oil and gas exploration, and a few small faults are known from geologic mapping. However, many earthquakes occur away from the few known faults, so there must be additional, unknown faults that can generate earthquakes in the seismic zone. Accordingly, the best overall guide to seismic hazard in the New Madrid seismic zone is the earthquakes themselves.

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