Saturday 17 October 2015

Magnitude 3.4 Earthquake in Ripley County, Missouri.

The United States Geological Survey recorded a Magnitude 3.4 Earthquake at a depth of 17 km, in northern Ripley County, in southern Missouri, slightly after 3.25 pm local time on Friday 16 October 2015 (slightly after 8.25 pm GMT). These are no reports of any damage or injuries associated with this event, but people have reported feeling it locally.

The approximate location of the 16 October 2015 Ripley County Earthquake. Google Maps.

Southourn Missouri 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 accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organization Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.

See also...

A pair of giant sinkholes have appeared at the Top of the Rock Golf Course in Taney County, Missouri, on Friday 22 May 2014. The larger of the two sinkholes measures 25 m across by 10 m deep, while the...

The United States Geological Survey recorded a Magnitude 3.6 Earthquake at a depth of 10 km, roughly 3 km to the south of the city of Steele in Pemiscot...

The United States Geological Survey recorded a Magnitude 2.8 Earthquake at a depth of 7.7 km, roughly 4 km to the west of the city of Malden in Dunklin...

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