Underground fault line in Missouri once caused major earthquake. Could it happen again?

The United States Geological Survey released a report at the beginning of this year looking at the risk of earthquakes around the country. The hazard map was colored in red along the West Coast, Alaska and Hawaii, showing that these areas have the highest risk of earthquakes in the country.

The risk levels are lower in the middle of the country, except for one big red spot in the middle of the country — in Missouri.

The town of New Madrid, which sits in the southeast corner of Missouri an hour away from Cape Girardeau, is home to fault lines where hundreds of unnoticeable earthquakes happen yearly, according to the Missouri Department of Natural Resources .

But they might not always go unnoticed. The USGS says that the region has a 25%-40% chance of a magnitude 6.0 or higher earthquake happening in the next 50 years, and as much as a 10% chance of a repeat of the damaging quakes that happened more than 200 years ago. And governments are starting to prepare for the possibility.

Missouri’s earthquake history

The Missouri Department of Natural Resources reports that from Dec. 16, 1811, to Feb. 7, 1812, three major earthquakes believed to be magnitude 7.0 or greater occurred in what’s now the New Madrid Seismic zone . These earthquakes were felt as far away as Louisville, Kentucky, and Cincinnati.

The earthquakes dropped the town of New Madrid 15 feet. Approximately 5,500 square miles, or about 3.5 million acres, of the Mississippi and Ohio river valleys were impacted by landslides, fissures, sandblows, lateral spreads, subsidence, submergence and uplift.

Single-story log buildings, which are an earthquake-resistant type of construction, shifted or sunk as parts of the areas submerged and flooded. Most of the area became unusable for the subsistence-type agriculture of that day.

Is there a tectonic plate in Missouri?

Scientists say there aren’t any tectonic plate boundaries in Missouri, but rather there are fault lines that can cause earthquakes. It’s one of the things that makes the natural disaster happening in the region so odd, said Eric Sandvol, a seismologist at the University of Missouri.

“Most earthquakes occur at the edge of these plates, like in California where we find the boundary between the Pacific and North American plates,” he said.

But faults are a tough area for researchers to study since the faults that produce earthquakes aren’t easy to see at the surface in the region, the USGS says.

The faults that produce earthquakes in the New Madrid region have been eroded by river processes and buried 100 to 200 feet deep by river sediment.

The seismic zone is located in southeastern Missouri, northeastern Arkansas, western Tennessee, western Kentucky and southern Illinois. Cities that are most likely to be affected include Memphis and St. Louis, as they are in the “splash zone” that could feel tremors.

An earthquake in this area can be more dangerous than what’s recorded on the West Coast, the Missouri department said.

“Due to the nature of the bedrock in the earth’s crust in the central United States, earthquakes in this region can shake an area approximately 20 times larger than earthquakes in California,” the Missouri Department of Natural Resources said in a blog post.

It’s not likely that Kansas City would suffer significant damage since the city is six hours away from New Madrid, but Sanoval said, that there’s a possibility it could be felt within the city. It’s documented that a bell was rang in Charleston, South Carolina, a 12-hour drive from New Madrid, as a result of the earthquake 200 years ago.

What kind of damage could an earthquake do in Missouri?

Researchers say you can’t predict when an earthquake is coming , but they have estimations on the damage an earthquake could do in the New Madrid seismic zone.

Chris Cramer, a geophysicist who works on earthquake hazard at the Center for Earthquake Research and Information at the University of Memphis , spoke to Undark, a nonprofit science news organization about the potential cost. He estimated that a major earthquake near New Madrid would cost the U.S. an average of $10 billion a year for 100 years from damaged buildings and lost infrastructure

The main cause of damage and injuries during an earthquake is the destruction of manmade structures.. These structures are prone to damage, according to the state department:

• Tall structures like buildings, bridges and dams
• Large open structures like auditoriums, classrooms, factories, hospitals and churches
• Brittle structures like unreinforced masonry buildings and unreinforced concrete
• Complex structures with odd shapes and lots of corners
• Unanchoredlarge objects in buildings like bookshelves, file cabinets, storage racks, pipes, fire sprinkler systems, water heaters and mechanical equipment.

National Guard task forces in the area of the New Madrid Fault in Missouri are training for an earthquake for the first time ever, according to Spectrum News in St. Louis . Cities in the seismic zone, like Memphis and St. Louis, have started to retrofit bridges in preparation. Newer buildings, especially taller ones, are built with shaking in mind, Undark says.

Undark reports that states in the New Madrid seismic zone — like Arkansas, Illinois and Kentucky — only included earthquake provisions in their building codes in the early 2000s, meaning anything built prior to that is prone to collapse.

In Tennessee, jurisdictions can decide whether to opt in to building codes with earthquake provisions.

In contrast, Missouri doesn’t have statewide building codes , although a bill was introduced this year to try and change that.