Monday Mar 26, 2018
The New Madrid Fault Line
Monday Mar 26, 2018
Monday Mar 26, 2018
In this episode of Memphis Type History: The Podcast, Rebecca reveals to Caitlin her recent paranoia of the New Madrid fault line and the seriousness of "the big one" for Memphis should it ever occur. But there's good new! Well... at least for those over 36 years old.
So what is the New Madrid Fault Line?
Wikipedia says it's the 150-mile (240 km) long seismic zone, which extends into five states. It stretches southward from Cairo, IL; through Hayti, Caruthersille and New Madrid, MO; through Blytheville into Marked Tree in AR. It also covers a part of West Tennesse, near Reelfoot Lake, extending southeast into Dyersburg.
That's a pretty big stretch of land.
The History of New Madrid Seismic Zone (NMSZ) Earthquakes
The first known written record of an earthquake felt in the NMSZ was from a French missionary traveling up the Mississippi with a party of explorers. It happened at 1 p.m. on Christmas Day in 1699 at a site near the present-day location of Memphis.
However, most famous was a series of 3 earthquakes between 1811-12.
The first earthquake was recorded at 2:15 am in Northeast Arkansas. It caused only slight damage to man-made structures, mostly because it wasn’t greatly populated. Memphis (before it was Memphis) was shaken at a Mercalli Intensity scale of level nine. Little Prairie, MO was destroyed by soil liquefaction, trees were knocked down and riverbanks collapsed. Uplifts of the ground on the riverbed and large waves made the Mississippi river look like it was flowing upstream. Sand bars and points of islands gave way. A steamboat crew that was anchored overnight along a Mississippi River island said they awoke to find the island had disappeared below the water. Landslides covered an area of 78,000 - 129,000 square kilometers, extending from Cairo, Illinois, to Memphis, Tennessee, and from Crowley's Ridge in northeastern Arkansas to Chickasaw Bluffs, Tennessee. This event shook windows and furniture in Washington, D.C., rang bells in Richmond, Virginia, shook houses in Charleston, South Carolina, and knocked plaster off of houses in Columbia, South Carolina. Observers in Herculaneum, Missouri said it had a duration of 10-12 minutes. After all this, only one life was lost in falling buildings.
The first and largest aftershock happened that same morning at around 7:15am. It came to be known as the “Dawn” Aftershock.
The second earthquake, on January 23, is believed to be the smallest of the three main shocks and also believed by some that the epicenter was in southern Illinois. That raises concern because if that is true, then that would mean and extended section of the fault exists.
The third earthquake, on February 7, happened in Missouri and it was the largest of the series. It destroyed the town of New Madrid, it damaged many houses in St. Louis. It caused general ground warping, ejections, fissuring, severe landslides, and caving of stream banks. Uplift along the fault created temporary waterfalls on the Mississippi River and caused the formation of Reelfoot Lake.
NMSZ Fun Facts: (because we try to make light of dark topics)
• There’s a New Madrid Historical Museum in the Missouri boot heel. There you can watch a VHS tape they play on loop, called “The Night the Earth went Crazy.”
• In 1990, there was an earthquake hype. A prophecy had just been made by a self-proclaimed climatologist named Iben Browning, who falsely claimed to have predicted the 1989 Loma Prieta earthquake in California the year before. He predicted that a magnitude 7 earthquake would strike New Madrid on December 3, 1990. The prediction had no scientific legitimacy but it was widely reported in the national media, which promoted fear, anxiety, and hysteria among residents of the Mississippi Valley.
• In Memphis, the city recently spent $25 million to prevent the pyramid from being swallowed.
• AutoZone’s corporate headquarters also stands ready for some massive shakes. It’s propped up on top of giant shock absorbers.
• The nearby Memphis VA is another safe spot. The city spent $64 million dollars removing nine floors of the hospital to reduce the risk of collapse in a catastrophic earthquake.
And if you would like more hope, we talk about Seth Stein, a seismologist and professor at Northwestern who doesn’t think we should be worried about the New Madrid. Rebecca talks about his theory on the episode which sounds pretty solid.
But for all you Eeyores and Debbie Downers, Rebecca also talks about how scientist say Seth's scenario is a low probability scenario and that the NMSZ is still hazardous. They estimate that over the next 50 years, the probability of a magnitude 6 or larger quake is between 25 to 40 percent.
In short, if you are 36 years old or younger, there is a good chance you will experience an earthquake in the Mid-South that measures higher than a 6.
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