Earthquake swarm hits area near New Madrid fault line in Missouri. What does it mean?

A swarm of earthquakes rattled along the New Madrid fault line, sparking fear of the “big one” shaking the area known for tremors.

Centered in New Madrid, Missouri, the seismic zone “is the most active seismic area in the United States east of the Rocky Mountains,” according to the Missouri Department of Natural Resources. The fault line includes areas of Missouri, Arkansas, Tennessee, Kentucky and Illinois.

The area has hundreds of small earthquakes annually, though many are not felt, officials say. Scientists indicate a large tremor with a magnitude of 7.0 or higher is possible in the next 50 years.

The morning of Monday, Dec. 9, residents in southeast Missouri felt the fault’s effects first-hand. Seven earthquakes shook the area in a nine-hour span, according to data from the University of Memphis Center for Earthquake Research and Information and emergency management officials in Indiana.

The tremors ranged in magnitude from 1.8 to 3.0, the largest occurring at 6:27 a.m. near Howardville, officials say. Six were centered closest to towns in Missouri, and the seventh was in northwest Tennessee.

So what does it mean?

The swarm is a sign of activity along the seismic zone, though it does not necessarily mean a significant one is coming.

The area has not had a significant quake in more than 200 years. In the winter of 1811 and 1812, there were three earthquakes in the area “estimated to be between magnitude 7 and 8,” according to the U.S. Geological Survey.

The series of earthquakes destroyed settlements and “dramatically affected the landscape,” officials said. They were considered the “biggest earthquakes in American history,” New Madrid officials said.

Should another one occur along the underground fault line, it could be “catastrophic,” according to Brian Houston, director of the University of Missouri Disaster and Community Crisis Center.

“Geologists have been forecasting when another one of these large earthquakes could occur in the NMSZ,” he said in 2023. “We’re overdue for another one, and models have predicted that if a large earthquake occurred now, it could be a catastrophic, multi-billion-dollar event for the region.”

A 2004 report prepared by FEMA indicated a 7.7 earthquake occurring in the seismic zone would cause $296 billion in damage, the Missouri Department of Natural Resources said.

The fault line includes major cities, such as Memphis, St. Louis and Little Rock, according to Missouri officials.

“As far as we know, there’s probably going to be more large earthquakes in the future, but we don’t know when because there’s no way we can predict earthquakes,” Tom Pratt, coordinator of the USGS Earthquake Hazards Program, told KSDK in July. “The time in between large earthquakes tends to be about 500 years or so, but that doesn’t mean large earthquakes or smaller ones couldn’t happen tomorrow.”