New Madrid earthquakes: imminent destruction coming soon?

The ground shakes, trees fall down, buildings collapse and the death toll rises– and this is all just the beginning.

Many fear the occurrence of such a scene and for people living near the New Madrid fault, the prospect of such a cataclysmic event is not too far-fetched. The fault has proven to be a dangerous producer of large earthquakes in the past and the next big one could happen at any time, any day or night.

Martin, Tennessee is not directly above the New Madrid fault, but is close enough to be threatened and there are associated faults near UTM. In fact, Martin is considered to be within the New Madrid Seismic Zone and is, therefore, considered at risk from the next big earthquake.

“The New Madrid Seismic Zone (NMSZ) is the most active seismic area in the United States east of the Rocky Mountains,” according to the Missouri Department of Natural Resources. “The NMSZ is located in southeastern Missouri, northeastern Arkansas, western Tennessee, western Kentucky and southern Illinois. Southwestern Indiana and northwestern Mississippi are also close enough to receive significant shaking from large earthquakes occurring in the NMSZ.”

The New Madrid Fault produced a series of large earthquakes starting 205 years ago in December of 1811 and finally ending the next year in February of 1812. These quakes are considered by geologists and historians to be the largest earthquakes in the history of the continental United States. According to the United States Geological Survey, the four biggest earthquakes were all magnitude 7.0 or higher. It is difficult to know exactly how large they were because modern equipment designed to measure earthquakes did not exist in 1811 and 1812.

The New Madrid fault is named after the town of New Madrid, Missouri, which was destroyed by one of those large earthquakes.

The earthquakes were so big, though, that they were felt much farther away than Missouri. In addition to destroying New Madrid, at least one was felt as far away as New York, and the earthquakes even rang church bells as far away as Boston, Massachusetts.  In Tennessee, residents of Nashville and Knoxville experienced the earthquakes. Tennessee’s Reelfoot Lake was created by one of those massive earthquakes.

However, there are probably no historical records of the earthquakes’ effects on Martin, Tennessee, because the town was not founded until years later in the 1870s. If there was any effect on people in the Martin, Tennessee area, not much is known about them because they simply did not write about it or what records there were no longer exist. There probably would not have been many people around to experience the events, except perhaps for some Native Americans who did not keep written historical records. There is at least one Native American legend which alludes to the events. In that legend, the famous Shawnee Chief Tecumseh caused the earthquakes of 1811-1812 when he stomped his foot.

Dr. Michael Gibson, a Professor of Geology at UTM, says there are still nearby and visible signs left by those earthquakes from over 200 years ago.

“Reelfoot Lake itself is the remnant of the quake most would point to. The quake caused land to subside and then fill with water from the Mississippi River. The surface faults are visible around the lake if you know where to look or read a topographic map. Mostly what people will see are linear scarps (slight changes in elevation) traceable for long distances. Sand blows occurred during the quakes that jetted sand into the air that fell as patches in the floodplains. Farming has mostly destroyed these, but some of the larger ones are still visible from air. Along the Chickasaw Bluff there is abundant evidence of the many landslides caused by the earthquakes,” Gibson said.

If an event like the ones in 1811 and 1812 happened today, UTM and the city of Martin would not be safe from it. Certainly, buildings would suffer damage. Many would probably fall. People could get injured or killed. There is a high possibility that surviving citizens would be left without running water, electricity, or the ability to communicate via cell phones or the internet. The roads could be damaged by the event, so transportation is not a given luxury. Citizens in need of help might not receive assistance from police, hospitals, or government agencies for a long time, depending on the availability of resources. That is especially true if relief efforts focus on larger population centers than Martin, such as Memphis or Nashville.

Because the affected areas were so rural and so thinly populated during the 1811-1812 events, the damage and death toll of the earthquakes were minimal compared with what could happen now.

“Very large quakes (8-9 moment magnitude) would be extremely devastating to the point of being ‘catastrophic.’ If the 1811-12 tremors were to occur today, with our increased population, cities, and dependence on technology and transportation, the result would probably be the worst natural disaster in American history. The 1811-12 quakes were felt from Canada to Mexico. We are in the middle of the country, so a quake of that proportion would affect all of the country to some degree, even if they didn’t actually feel the quake,” Gibson said.

Some people believe we are overdue for the next big earthquake because it has been so long since the last one. However, saying it is overdue puts a simple label on a complex issue.

“Overdue means we know the precise timetable for earthquakes, which we don’t. We only have a few data points for large events to work with to establish the recurrence interval of quakes in our area. Seismologists are determined that we have about a 50% probability of a 6.3 quake sometime in the next 20 years. That probability rises to 80-90% of occurrence within the next 50 years. Larger earthquakes have a lower probably, which is good. Estimates are that we should expect, on average, one quake of 8.3 or greater magnitude every 500 years, giving us a 2-7% chance of an earthquake that size in the next 50 years, but that can be misleading as we have so few data points to work the statistics and averages are not true predictions. As for the ‘big one,’ we never know the ‘big one’ has occurred until after the earthquakes have all happened over an extended period of time. Establishing which was the biggest is a historical designation,” Gibson says.

Nothing can be done to stop an earthquake from happening, and nothing can be done to accurately predict the day, time or size of one, so worrying about it does not help much. However, UTM has done what it can to prepare.

“UTM buildings are built to ‘code’ and most newer buildings have been constructed with reasonable earthquake design included. However, older buildings may be more vulnerable as they have aged and even the most well-constructed buildings will be at risk in the largest quakes. How large is difficult to say – different buildings will probably respond differently,” Gibson said.

Additionally, there are procedures for earthquakes that can be followed when they hit the campus of UTM.

“These are posted in the disaster plans and on the website for UTM (https://www.utm.edu/alerts/earthquake.php). Essentially take cover and avoid areas where debris can fall, etc. Be prepared to be on your own for all needs such as food, water, medical help, etc. for a couple of weeks if we were to get a really large event,” Gibson said.

The New Madrid Seismic Zone is more active than many people might think. The truth is that we survive earthquakes pretty often.

“Microseismic earthquakes (magnitude less than 1.0 to about 2.0), measured by seismographs but not felt by humans, occur on average every other day in the NMSZ (more than 200 per year).” According to the Missouri Department of Natural Resources.

On April 27th, 2016, Dr. Michael Gibson was asked when the last local earthquake was. His response was attention getting.

“Well, if we count the very small events…today! If we only count something felt, then our seismometer indicates the most recent was a 1.9 M event Tue Apr 26, 03:32:52, 2016, 10.10 km depth 7.70 km (4.78 mi) southwest of Tiptonville, TN.”

Gibson says that he worries about flooding more than major earthquakes in the Martin area because they more often pose a threat, so he has insurance for both.

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