Tornadoes, flash flooding and hurricanes may be the only natural disasters Mississippians are used to, but the possibility of another destructive force could be in the state’s near future.

The New Madrid Seismic Zone (NMSZ) stretches to the southwest portion of the U.S. from New Madrid, Mo. and is responsible for the largest earthquake in United States history.

In 1811 and 1812, the NMSZ caused a series of earthquakes that measured at a magnitude of 8.0 and were so violent that church bells rang in Boston, furniture moved in the White House and some reports say the Mississippi River temporarily flowed backwards said Terry Panhorst, assistant professor of geology and geological engineering at the University of Mississippi.

“When you talk about a magnitude of 8.0 you are talking about 10 times larger than the Haiti earthquakes that happened last month,” said Haydar Al-Shukri, director of the Arkansas Earthquake Center at the University of Arkansas at Little Rock.

The Arkansas Earthquake Center has been studying the fault since 1974 and reported that there have been more than 4,000 recorded earthquakes (about 200 a year) since that time, most of which were of magnitudes of 3.0 or below.

The United States Geological Survey (USGS) reported that earthquakes with a magnitude of 7.0 or greater reoccur approximately every 500-600 years along the NMSZ.

A medium-sized earthquake ranges around 6.5 in magnitude and occurs approximately once every century, with the last medium sized earthquake along the NMSZ in 1898.

“We’re sort of overdue for a medium-sized earthquake, so I kind of expect one in the next few years in the New Madrid; that means it may be in Illinois but it could be in Marked Tree, Ark. too,” Professor Charles Swann, associate director of Mississippi Mineral Resources Institute, said.

The way earth scientists measure the possibility for earthquakes is similar to the way meteorologists forecast weather by predicting the probability of when an earthquake could occur within a specific time interval.

What are the chances?
“The problem with earthquakes is they don’t necessarily follow a pattern; they follow the pattern that they want to follow,” Panhorst said. “I wouldn’t necessarily characterize it as being overdue because that could set a tone of alarm, but we have to be aware that it should not be unexpected for something of that seismic event to occur.”

The USGS reported that by using data produced by the National Seismic Hazard maps and the Center for Earthquake Research and Information at the University of Memphis, it is estimated that the probability of an earthquake with a magnitude of 6.0 or larger (medium-size) is about 25-40 percent, with a 7-10 percent chance of a 7.5 - 8.0 magnitude (large-size) within the next 50 years.

With largely populated cities along the NMSZ including Memphis and St. Louis, there has been much concern as to the extent of damage and the risk for a high casualty count.

“If you have a magnitude 6.0 in the zone there is going to be damage in Memphis, there is no question about that, but the question is how extensive is the damage going to be,” Panhorst said. “But Memphis has taken some steps to try to mitigate that situation to alleviate the extent of the damage.”

What about Ole Miss and Oxford?
The University of Mississippi has also recognized the potential of an earthquake from the NMSZ and has taken the lead on earthquake mitigation in Mississippi.

The Disaster Resistant University Committee, which handles campus and community emergency readiness, has been working with the Mississippi Emergency Management Agency (MEMA) and Mississippi Mineral Sources Institute to help mitigate such an event.

The primary region of destruction heavily depends upon what region of the fault zone the earthquake occurs in. Were it to occur in the southern portion of the seismic zone, it would hit cities closer to Memphis and Jonesboro, Ark.

“The area that we think would be most heavily impacted would be the northwest part of the state,” said Jeff Rent, information officer for Mississippi Emergency Management Agency. “The unique geology and soil composition of the Delta, with its liquid faction, we would see some sinking of some structures into the earth because of that.”

Liquid faction is when a relatively solid material mixes with a liquid causing the material to liquefy and lose all strength, which is a problem in the Delta because it is part of the Mississippi River floodplain.

Which buildings would be affected?
In the event of an earthquake, the soil content would play an important role in the extent of damages.
For example, the saturated soil of the Delta would cause the waves to be amplified. The soil on campus, however, is estimated to be 50 million-year-old sand, which is very solid.

“There’s not that much of a population center in the Delta with high rise construction but that type of construction is usually sparse and there are a few concentrations,” said Christopher Mullen, NTERIM chair and associate professor of civil engineering. “For example, where the casinos are and those will have the benefit of newer building codes. Some of the older buildings without reenforced masonry are considered the most vulnerable and would not have the benefit of some of the new seismic detail that building codes required.”

The newer buildings are subject to the international building code, which is a policy of the Mississippi Institutions of Higher Learning and design professionals are obligated to consider the provisions for earthquakes in the building codes.

“Most of the damage that is going to happen is going to happen in the old building that never followed a building code, so the older buildings built out of stiff material, such as concrete blocks and cinder blocks, will take the most damage,” Al-Shukri said.

Infrastructure including roads, bridges, gas lines and water mains, is assumed to be where North Mississippi would take the biggest hit, especially certain gas pipes that are along the NMSZ.

“This is concern of some people because what you’re going to end up doing is having a much greater effect away from this area than you think about,” Panhorst said. “If those lines get severed you could potentially have gas and oil dumping into the Mississippi River and also shut down all of that fuel into the northeast, and how many days is that going to be shut down?”

Despite this, MEMA said they are ready should the NMSZ cause an earthquake in the future.

“The state legislature really takes emergency management seriously, as does the governor, and they have supported us tremendously since Katrina,” Rent said. “They realize what an important thing having a good emergency response and emergency management means; it saves lives, property and is critically important.”