Thursday 13 December 2018

Magnitude 4.4 Earthquake in Meigs County, Tennessee.

The United States Geological Survey recorded a Magnitude 4.4 Earthquake at a depth of 11 km, roughly 11 k to the northeast of the town of Decatur in Meigs County, Tennessee, slightly before 4.15 am local time (slightly before 9.15 am GMT) on Wednesday 12 December 2018. These are no reports of any damage or injuries associated with this event, but people have reported feeling it in Tennessee, Missouri, Kentucky, Illinois, Indiana, Ohio, West Virginia, Virginia, North Carolina, South Carolina and Alabama.

The approximate location of the 12 December 2018 Meigs Earthquake. Google Maps.
Tennessee lies within an area known as the New Madrid Fault Zone, an seismically active area which lies over the deeply buried Reelfoot Rift, an area of tectonic expansion associated with the breakup of the ancient supercontinent of Rodinia about 750 million years ago. This is no longer an active rift, but it is an area of weakness within the North American Plate which is more prone to movement in response to other tectonic stresses, such as the compression of the plate by expansion beneath the Atlantic and Pacific Oceans.
The Reelfoot Rift is overlain by a deep layer of poorly consolidated tertiary sediments. These sediments are prone to liquefaction during tremors. When this occurs the sediments behave as a liquid, rather than a solid, with often devastating consequences for man made structures such as buildings and roads on the surface.
 The structures underlying the New Madrid Fault Zone. Geological Survey of Alabama.
The New Madrid Fault Zone gets its name from the New Madrid Earthquakes of 1811-12, which were felt over much of the central United States, entirely destroying the city of New Madrid, Missouri, and causing damage to buildings as far away as St Louis, Missouri and Memphis Tennessee as well as diverting the course of the Mississippi River.
Witness reports can help Geologists understand Earthquake events and the underlying structures that cause them. If you felt this quake (or if you were in the area but did not, which is also useful information) you can report it to the United States Geological Survey here.

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