What If 'The Big One' Rocked St. Louis?

This winter is the bicentennial (200th) anniversary of three New Madrid earthquakes that shook not just Missouri, Illinois. Kentucky and Tennessee, but were felt as far away as New York City, Washington, D.C. and Charleston, South Carolina.

The New Madrid earthquakes on December 16 (1811), January 23 and February 7 (1812) are considered by the U.S. Geological Survey (USGS) to be the fifth, sixth, and seventh largest earthquakes ever in the continental United States.

The first and third quakes were estimated at 7.7 in magnitude, according to the USGS, and the January quake was a mere 7.5.   

St. Louis suffered the most damage from the February quake, the last of the three. There was some severe structure damage and toppled chimneys. The USGS reported that Louisville, and as far away as Nashville, suffered some extreme disturbances.

The first person I contacted hoping for an estimate of the damage that would be suffered today from similar quakes was Professor Ian Prowell at the Missouri University of Science and Technology. He came to MUS&T from California with a background in seismic research.

He directed me to a website, The Great Central U.S Shake Out, a consortium headquartered in Memphis that described a scenario of a 6.5 magnitude quake in New Madrid. 

They estimated 100 deaths and 2,500 injuries, but the worst St. Louis would suffer would be some “shaking damage.”

However, a 6.5 magnitude earthquake is not a 7.7 magnitude quake—something which some experts call “a once in 300 year event.”

So now 200 years have passed since the trio of giant shakers.

Mark Croarkin, a MoDOT District Engineer who specializes is bridges, is confident the recent bridge retro work will withstand quakes in 5-6 magnitude range. But he admits a 7.7 is something completely different.

“We spend a lot more time on double-decker structures after what happened in 1989 in San Francisco (a 6.9 quake),” Croarkin said.

“Keep in mind there is no such thing as ‘earthquake proof.’ There is also a question of how much money you want to, or can spend.“

“A 7.7 earthquake—FEMA (Federal Emergency Management Administration) comes in and takes over the whole state,” Croarkin said.

“If you are a first responder and it is a 7.8 quake, you take care of your family first and then respond. It is going to be that serious even if it originated in New Madrid,” he said.

Croarkin explained that the New Madrid area is perhaps the toughest to prepare for.

“There are not fault lines like they have in California. Around New Madrid, there are rifts that are small splits in a plate. They are hard to identify. Much of the area is solid limestone that will tremble a long way,” Croarkin said.

Several other construction and traffic engineers said in a huge earthquake the smaller bridges would be some of the biggest problems. These would be like the I-64 bridges over Olive/Clarkson or Highway 141.

Those bridges would likely fall flat onto the road below.

Think of all the bridges along I-64 from just Brentwood Boulevard to the Missouri River.  

If there is major damage toward the southwest of St. Louis, Manchester Road and Route 100 would be a least-affected road, because it has the fewest bridges. It would be cleared first and used to send help and relief supplies. But past I-270 along Manchester, there are still bridges at Highway 141, the Meramec River and I-44.           

Mike Geisel, who wears three important hats in Chesterfield, as the planning director, public works director and city engineer, shared his belief that St. Louis would be affected if there was a 7.7 magnitude earthquake in New Madrid.

But he thought Chesterfield would suffer less damage than older communities in the region.

“I do, however, have a great deal of confidence in both our modern building codes as well as County's enforcement of same. Chesterfield is in a good position due to the relatively new construction," Geisel said.

There will be damage. Substantial damage! There will be structures completely lost in a severe earthquake and substantial damage to our infrastructure. 

Roads, bridges, but even more importantly are our utilities, e.g. gas, electric, and communications. There are a lot of hidden hazards,” Geisel said, in response to our inquiry.

On Tuesday, February 7 at 10:15 a.m., there will be an earthquake drill, 200 years to the day of the final New Madrid 7.7 magnitude earthquake.

It will be interesting to see how much publicity this drill gets.