Earthquakes In Louisiana?

Kerri Cooke Thursday, December 9, 2021 Comments Off on Earthquakes In Louisiana?
Earthquakes In Louisiana?

A Rarity But Not Unheard Of

By Kerri Cooke

With earthquakes recently rattling Alaska and Hawaii, and the never-ending discussion over whether and when California will have a severe earthquake along the San Andreas fault, you may wonder if there’s any risk of an earthquake shaking Louisiana. While you might, justifiably so, believe the risk of an earthquake in Louisiana is zilch, you would be wrong. Louisiana is, believe it or not, in an earthquake zone. 

Louisiana has a history of earthquakes, though none of great size. And I’m sure you’ve heard of small earthquakes taking place in the Gulf of Mexico off the Louisiana coast. Fault lines run along the Gulf Coast of Louisiana from west to east or east to west (whichever way you prefer to look at it). They continue up into Beauregard Parish and stretch eastward to right above Lake Ponchartrain. There are also a few faults in northwestern Louisiana.

However, these faults are different than the faults that cause major earthquakes. The faults are natural and shallow growth faults. In other words, you might notice a rise in the ground near the faults as the earth rises. The Earth’s crust is slowly moving and there is not the risk of extreme pressure causing rocks to break that you get with large earthquakes.

Many of Louisiana’s fault lines were discovered due to oil and gas exploration. However, for a while the extent of the faults in southern Louisiana was unknown because they run through unpopulated or sparsely populated areas.

The most notable of Louisiana’s fault lines run through Baton Rouge. There is a rise in the road along College Drive, just a little north of the intersection of College Drive and Corporate Boulevard. Evidence that these faults are active is minor damage, specifically cracking, in buildings and sidewalks near the faults, specifically in Baton Rouge, Scotlandville and Denham Springs.

October 19, 1930

The largest earthquake in Louisiana’s history, estimated at a magnitude of 4.2, woke up residents in New Orleans on Oct. 19, 1930. The epicenter is said to have been Donaldsonville. Local seismographs were not operating at the time, but the earthquake registered on a seismograph in Washington, D.C.

The quake caused pictures and other objects to fall off walls, windows to crack and light fixtures to swing. New Orleans rocked for an estimated six to 15 seconds. According to the Oct. 20, 1930, issue of the Times Picayune, “In some instances, beds were rolled two or three feet, causing their occupants to awaken startled, pictures to loosen from walls, dishes to rattle, and house foundations to creak loudly.” The quake was also felt to some degree in Baton Rouge. 

October 15, 1959

Believe it or not, an earthquake centered in the Grand Chenier and Creole area hit in 1959. The magnitude is estimated to have been a 3.8 and some rattling was noted. The quake was felt from Cameron all the way to DeQuincy.

April 24 To August 16, 1964

A series of earthquakes took place between April and August of 1964. However, most of the earthquakes were in Texas but so close to the state line that they were felt as if they were in Louisiana. The earthquakes usually averaged between a 3.0 and 4.0 magnitude. What makes these quakes interesting is they occurred while the Toledo Bend Dam was being built and the Sam Rayburn Reservoir was being filled.

October 16, 1983

Sulphur experienced a 3.8 magnitude earthquake on Oct. 16, 1983. It was, at the time, the only earthquake in the state to have been registered and located by local instruments. Whether this is still the case is not clear.

Recent Quakes

We’ve had three earthquakes in Louisiana in 2021, and they’ve all taken place in the same general area — in the northwestern part of the state near the Texas border, specifically the Blanchard area. The last time before 2021 Louisiana had had a quake was in 2018. All of these quakes were of low magnitude and probably barely if at all noticeable on the surface. Louisiana went entirely without any detectable quake from 1983 (the Sulphur earthquake) until 2005. The areas with the highest cluster of detectable quakes are northwestern Louisiana, along the border with Texas and in Arkansas, barely over the Louisiana state line. So while Baton Rouge faults might be the most notable, they rarely cause detectable quakes. 

And earthquakes don’t seem to be becoming more frequent. There can be long spans of time between earthquakes. While we’ve had three earthquakes this year, they are all minor and within the same general area. They’re also not too far from where the Toledo Bend quakes happened in 1964, so infer what you may.

New Madrid Seismic Zone

While Louisiana has had a number of quakes, the risk for earthquakes in Louisiana is still very low. And when we do have earthquakes, they are minor since the local faults are not the type to typically produce earthquakes, especially not deep and forceful ones.

However, Louisiana is in decent proximity to the New Madrid Seismic Zone, which includes northeastern Arkansas, southeastern Missouri, western Tennessee, western Kentucky and southern Illinois. This area has historically recorded some of the most powerful earthquakes in recorded U.S. history. The proximity of the seismic zone to Louisiana poses more of an earthquake risk than local quakes do in Louisiana. The quakes occur along wrench faults, which date back thousands of years — back to the time when the continents separated from the one land mass know as Pangaea. These wrench faults are said to be places of crustal weakness.

There were three major earthquakes in the New Madrid Seismic Zone between Dec. 16, 1811, and Feb. 6, 1812. These earthquakes are estimated to have been of a 7.0 magnitude or higher. In between the large quakes, were many small and middle range quakes. The largest quake happened on Feb. 7, 1812, and was felt in New Orleans. Eventually seismic activity in the area stopped. 

So while the threat of earthquakes is higher due to proximity to areas with high seismic activity, you most likely still don’t need to tie things down or bolt furniture into the walls like they do in California. However, if one day you feel a light swaying of the ground, it is not out of the question that you are experiencing a minor earthquake. 

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