The Illinois Emergency Management Agency is encouraging people to prepare for potential earthquakes in the wake of the 6.4 and 7.1 magnitude earthquakes that rocked southern California earlier this month. The events served as a reminder that, “earthquakes can happen anywhere in the world and at any time of day,” IEMA Acting Director Alicia Tate-Nadeau wrote in a press release.
Illinois is flanked on its western and eastern borders by two active seismic zones: the New Madrid Seismic Zone and the Wabash Valley Seismic Zone. The New Madrid Seismic Zone is made up of several thrust faults that stretch from Marked Tree, Arkansas, to Cairo, Illinois. On Dec. 16, 1811, and Feb. 7, 1812, two earthquakes devastated the town of New Madrid, Missouri, with damage reported as far away as Connecticut, South Carolina and Washington, D.C.
Those earthquakes were devastating at magnitudes of 7.5 or greater and were mighty enough to cause the Mississippi River to change course and go backwards for a while forming what today is known as Reelfood Lake in Tennessee, said Harvey Henson, assistant professor of geology and science education at the Southern Illinois University-Carbondale.
And it’s possible that could happen again.
According to Henson, there’s a 7 to 10 percent chance of a great New Madrid earthquake happening again in the next 50 years. And as for the magnitude, there’s a 25 to 40 percent chance the earthquake could be a 6 on the Richter scale or greater.
“It’s something that should concern all of us,” he said. “The potential damage the intensity could have from a Midwest earthquake covers a large area.”
That’s because the bedrock in the central and eastern portions of the United States is older than the rock layers out west, said Jim Wilkinson, executive director at the Central United States Earthquake Consortium. It creates a dilemma that’s unique to this portion of the country.
Wilkinson uses the analogy of throwing rocks in a pond to explain the difference.
“In one, on the West Coast, you’ve got things like cypress trees and structures in the ground that cause the ripples to bounce back when they hit something,” he said, saying the water rings represent earthquake episodes. “In our pond (in the Central U.S.), the rings don’t have anything to come back on. They just travel.”
That intensity could cause catastrophic damage in the region, said Robert Bauer, Principal Engineering Geologist for the Illinois State Geological Survey.
“The area of influence is about 10 to 15 times larger in the Central U.S.,” he said. “The faults that happen in California are when two plates that are on the Earth are moving against each other, but here it’s a crack inside a plate.”
Henson and his team at SIUC use imaging to study the layers of rock and evaluate what’s happening beyond the surface level. And because Southern Illinois is mostly flat, it’s hard for people to realize a great geological event could occur here.
“Not all is as it seems on the surface,” Henson said. “Our towns and cities have all come up around the rivers and we live in the floodplains of these rivers. Those type of geological settings don’t do well and amplify the weight energy. Materials could be saturated and potentially liquefy.”
That’s where agencies like the CUSEC, where Wilkinson works, step in.
The organization address the potential of earthquakes in multiple states where they could be a hazard and works with local, state and federal emergency management agencies to be as prepared as they can be, whether that’s making sure communities adopt stronger building codes or distribute educational materials.
Henson’s team is working to provide informational kiosks to distribute to communities in the state where earthquakes would have a devastating effect.
Every year, an event called “The Shakeout” operates as the world’s largest earthquake drill. This year, it will take place on Oct. 17, the IEMA said.
Tips to stay safe during an earthquake
The IEMA also offered several steps people can take to help prevent injuries and property damage at home, including:
- strapping water heaters and large appliances to wall studs,
- anchoring overhead light fixtures,
- fastening shelves to wall studs and securing cabinet doors with latches,
- strapping TVs, computers and other heavy equipment to prevent tipping,
- learning how to shut off gas, water and electricity in case the lines are damaged.
Following these rules in the case of an earthquake are essential, as most casualties result from falling objects and debris caused by the earth shaking, Tate-Nadeau said. She emphasized that the phrase “drop, cover and hold on” reminds people to drop down to the floor, take cover under a sturdy desk, table or other furniture and hold on to that object and be prepared to move with it until the shaking ends.
“While we cannot predict when the next major quake will occur, we can help people learn how to protect themselves and reduce damage to their homes.”