Emergency managers from the area gathered at Southeast Missouri Mental Health Center earlier this month to understand the potential effects of a major earthquake in the area.
Jeff Briggs is the earthquake program manager for the Missouri State Emergency Management Agency (SEMA). He presented a seminar on the damage forecast should a major earthquake event take place at some point along the New Madrid Fault.
“Historically this is the most active earthquake seismic zone in the United States east of the Rocky Mountains,” he said. “A little over 200 years ago, 1811 and 1812, a series of the very largest earthquakes in U.S. history hit right here in our backyard.”
Briggs explained that although one major earthquake will bring widespread devastation to the area, major earthquakes always come with aftershocks. Some can be as severe as the original tremblor.
“When earthquakes happen, there’s never just one,” he said. “There’s always aftershocks. The first big one happened Dec. 16, 1811, with a magnitude of 7.5. There were aftershocks of magnitude 6.1, 6.8, 5.0, and 6.0 — all the same day. There were dozens of smaller aftershocks for the next month or so and then five weeks later another big one magnitude 7.3.
“They kept on coming and then seven weeks after the first a third very large quake of at least a magnitude 7.5. If you’re living in southeast Missouri, how do you respond to this? Not only is your building damaged, your land is uprooted, but it keeps coming and you don’t know for how long.
“This is a unique challenge in terms of natural disasters for what we face at SEMA and what you will be working with locally based. It happens. There’s big damage but we know it’s going to keep on happening for quite some time.”
According to Briggs, part of the biggest problem for emergency management is that earthquakes are impossible to predict. There is usually time to prepare for floods and in recent years forecasters can predict tornadoes. Earthquakes appear without warning. This problem leads to geologists simply having to guess when a major earthquake can happen.
“Judging from the history and geology of this area, geologists estimate a 25-40 percent chance of a magnitude 6 or larger in 50 years,” he said. “There is a 7-10 percent chance of a magnitude 7 in the next 50 years.”
Due to the Mississippi and Missouri rivers, Briggs explained that Missouri has high damage potential along the eastern border all the way north to the Iowa border and into parts of central Missouri.
“Earthquake waves tend to travel well in loose, sandy, flat soil,” he said. “The whole New Madrid fault line runs about 150 miles right along the Mississippi River. The earthquake shock waves are carried very efficiently right along the rivers. This is a big reason that it’s felt so widely. In a big earthquake we’ve got to focus not just on the Bootheel area, we’ve got to focus on the entire state.”
The soil deposits along the rivers are very unstable when subjected to seismic waves due to a process called liquefaction. The damp, sedimentary soil compacts and forces the water to the surface and buildings will sink and lean. Roads and underground utilities will either heave upward or collapse. Briggs explained that when this pattern of quakes and aftershocks happen in other parts of the world, that type of land ends up being abandoned for any further construction.
“There are going to be places where people simply don’t rebuild,” he said. “People are going to leave the area, there will probably be a population decrease in the area because a lot of people will find it too difficult to live and rebuild in the heart of the seismic zone.”
As the geology of St. Francois County is less prone to liquefaction, there would be less of this type of concern compared to parts of St. Louis and other areas much farther away from the seismic zone where construction exists in major river bottoms.
An area of financial concern for property owners is that seismic damage is not covered by homeowners insurance. An earthquake insurance endorsement must be added to a policy. Briggs noted that many property owners might not be aware of this situation or can not afford it.
“A study from the Missouri State Department of Insurance found that only 20 percent of people have earthquake insurance,” he said. “You buy your standard homeowner’s insurance, but it does not cover earthquake and flood damage. You have to buy an endorsement that cost additional money. As you get closer to the New Madrid Seismic Zone, since the year 2000 the premiums have gone up more than 600 percent.
“If you decide you want that insurance, it typically comes with a 20 percent out-of-pocket deductible. If you have a $150,000 house, you’re still going to be out of pocket $30,000. For these reasons, it’s going to be a very difficult recovery process. Many homeowners are not going to have any money to rebuild.”
Briggs observed that the way a building was constructed will determine whether it will remain intact or not during a catastrophic earthquake event.
“The buildings at biggest risk are unreinforced masonry brick buildings — the old brick buildings,” he said. “The more modern, recently constructed masonry buildings have a lot of steel reinforcement in them. They will do better. Wood buildings will hold up well because wood has a little flexibility in it. If you think about downtown St. Louis, there are literally thousands of old brick buildings.
“That’s really going to be a big problem for the St. Louis area and any historic center. A lot of bridges are not built to withstand seismic events. Some have been retrofitted — had some reinforcement added to them. And some of the bridges that do survive — the approaches to them being dirt-filled — those might not survive.”
Briggs offered statistics showing that should an earthquake happen today on the scale of the 1811-1812 event, it has the potential to be by far the most expensive and deadliest catastrophe in American history.
“In an eight-state area it is predicted that more than 82,000 injuries and about 3,500 fatalities would occur,” he said. “Almost $300 billion in losses. More than 2.5 million people will be without power. More than a million people without water.
“This will last for quite a while. It’s going to be difficult to get in and restore these services. The aftershocks are going to keep happening, so if you get it fixed it might get damaged again. If you live in the seismic zone be ready to live on your own for at least two weeks.”
According to Briggs, the biggest risk of injury in the developed world after an earthquake is falling debris. Some basic tips for homeowners to reduce damage and injury include securing of water heaters by strapping them to the wall because this may be the only source of water after an earthquake; store heavy objects on low shelves; and anchor tall furniture to a wall or move it to where it can not fall over and cause injury.
During an earthquake, Briggs recommended taking these actions: If possible, crawl underneath a desk or table to shelter from debris; if in bed, turn over face down and cover your head with a pillow; and make sure ahead of time that there is nothing heavy that will fall on your bed.
If driving, pull to the side of the road. Make sure nothing nearby will fall on the vehicle and stay in the car. The car is one’s best protection against debris. If outside, a person should try to get away from anything that could fall on them. Instead, they should lay face down and cover their head with their arms.
For additional information, go to Shakeout.org for earthquake drill information.
“Historically this is the most active earthquake seismic zone in the United States east of the Rocky Mountains.” Jeff Briggs, SEMA
Mark Marberry is a reporter for the Farmington Press and Daily Journal. He can be reached at 573-518-3629, or at firstname.lastname@example.org.