Southern Illinois quake’s magnitude is area’s strongest in years

Editor’s note: This story has been updated to reflect that Tuesday’s earthquake occurred in the Wabash Valley Fault System.

An earthquake early Tuesday morning was the strongest on record in Southern Illinois in the past several years.

United States Geological Survey officials reported the 3.8 magnitude earthquake was centered near the town of Albion. An earthquake of that magnitude is often felt by people, but causes little damage.

“Intensity is based on the observed effects of ground shaking on people, buildings, and natural features,” USGS officials wrote. “It varies from place to place within the disturbed region depending on the location of the observer with respect to the earthquake epicenter.”

The quake occurred in the Wabash Valley Fault System, which runs along the Indiana and Illinois border — beginning just south of Indianapolis — and into parts of northeastern Kentucky.

However, the metro-east area of Southern Illinois falls into the New Madrid Seismic Zone, which includes Southern Illinois, most of southern Missouri and parts of many other Midwest and southern states, including Arkansas, Tennessee, Indiana, Ohio, Iowa and Mississippi. This zone is the most active seismic area in the country east of the Rocky Mountains, according to officials with the Missouri Department of Natural Resources.

“In the winter of 1811 and 1812, the New Madrid seismic zone generated a sequence of earthquakes that lasted for several months and included three very large earthquakes estimated to be between magnitude 7 and 8,” Geological Survey officials wrote.

A fault near New Madrid, Missouri, made the Mississippi River flow backward.

“New Madrid dwindled to insignificance and decay; the people trembling in their miserable hovels at the distant and melancholy rumbling of the approaching shocks,” Geological Survey officials wrote.

There have been numerous earthquakes along that New Madrid fault line for decades, leading officials to fear of a catastrophic earthquake.

Herb Simmons, director of St. Clair County Emergency Management Agency, told the BND he worries about the aftermath of an earthquake.

“We want to focus on New Madrid, that’s a serious thing I worry about more than anything. There would be calls for help from everywhere,” he said.

“We hear of all the minor quakes all around us even in the bootheel of Missouri. When you go and actually start seeing these (emergency plans), and the slides the experts are showing at EMA, it makes the hair stand up on the back of your neck,” Simmons said.

Earthquakes of magnitudes between 1.0 and 2.0 are measured by seismographs every day in the New Madrid Seismic Zone. However, people do not feel tremors of that magnitude.

The largest earthquake Southern Illinois has ever seen was recorded at a magnitude of 5.4 in 1968.

In February 2012, an earthquake of 3.9 magnitude was centered near Charleston, Missouri, a few miles southwest of Cairo, Illinois.

As for earthquakes centered in Illinois, this is the largest one since April 18, 2008, when a 5.2 earthquake rocked an area about 7 miles northwest of Mount Carmel, Illinois, which is about 140 miles east of Belleville and close to the epicenter of Tuesday’s earthquake.

Several aftershocks were recorded in the Mount Carmel area the day of and the days following that 5.2 earthquake.

An interactive map on the Geological Survey website allows users to see the areas which were affected by the Tuesday quake.

Simmons said he and other county leaders keep an emergency bag on hand with enough supplies to last for 72 hours. His emergency bag includes gloves, twine, water, food, a hand-cranked radio and a water filter.

“It’s what I worry about quite often because of the unknown — we don’t know when it’s going to happen,” Simmons said Tuesday. “Where it happened this morning, they didn’t have any warning it was coming. It’s not like tornadoes or storms that the National Weather Service can forecast, an earthquake just happens.”

This story was originally published September 19, 2017 at 7:35 AM with the headline "Southern Illinois quake’s magnitude is area’s strongest in years."