Earthquakes Near St. Louis
Why they are different from "coastal" earthquakes and what to do when one occurs.
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According to the U.S. Geological Survey, 4,000 earthquakes have occurred in the New Madrid Seismic Zone since 1974

On April 18th, 2008 a 5.1 earthquake struck near the southern borders of Illinois and Indiana. The epicenter was 19 miles SE of Olney, Illinois - close to the Ohio/Wabash rivers. A second earthquake followed less than 6 hours later just north of the region of the previous quake and registered a 4.6. This event was felt as far away as Atlanta, Georgia!

Earthquakes are more common in the Midwestern United States than most think. Because the tectonic plates in the central United States are older and cooler than those near our east and west coasts, the results of those events often cause more movement and damage than their coastal cousins.

The "New Madrid Earthquake" which occurred on February 7, 1812, was actually part of a trio of magnitude 8 events near New Madrid, Missouri. (Then part of the Louisiana Purchase) This was the most devastating earthquake in the history of our country. There were reports of this quake being felt strongly over a 50,000 square mile radius and moderately over a 1,000,000 square mile range. The historic "San Francisco" quake of 1806 was estimated to be felt moderately over a mere 6,000 square mile range.

Why is there such a difference? The rock under the Midwest region has had millennia to cool and harden. When an event occurs, the energy transfers much more efficiently over wide distances. The coastal regions are less rigid for many reasons. There is more frequent seismic activity and the sand and soil built up and pushed around for centuries is softer and more malleable.

The course of the Mississippi river was actually changed during the "New Madrid Earthquake." Reelfoot lake was created by the shift. Another smaller lake in Mississippi was also formed by the shifting of the river's course. What damage could an event in our modern times cause?

St. Louis and Memphis face potentially devastating consequences. Property damage could run into the billions of dollars and loss of life could be at levels which would dwarf Katrina's fury.

Earthquakes on the solid, stable rock of the Midwest tend to roll more than in coastal quakes. Because the tectonic plate is so hardened by centuries of cooling, it is much more difficult to crack. When a fault shifts, the energy takes more of a gradual, spreading method like the waves moving away from a stone dropped into a tranquil pond.

For the same reason, structures which are constructed of brick, stone or concrete are more likely to break or have catastrophic damage during an earthquake than more flexible frame buildings. Even minor tremors can cause the brick facade to break away and fall from buildings.

There is a saying among seismologists and others who specialize in the study of earthquakes and the resulting damage: "Earthquakes don't kill people. Falling debris and buildings kill most of the victims."

Experts advise anyone experiencing an earthquake to exit the building quickly if possible. They say the worst that will probably happen to a survivor who is outside might be a fall. If leaving is not possible, get into a doorway or under some support structure which will protect you from falling debris.

If you make it outside or are outside when the tremor begins, move away from buildings to avoid falling bricks or other material.

The duration of the shaking or rolling can be a few seconds to minutes. Events like the New Madrid quake opened chasms and changed the course of a mighty river so death and injury are possible. But common sense and a little careful planning may prevent some damage and injuries.

Stories about that great earthquake vary but there seems to be a consensus that the reason so few lives were lost is directly related to the fact that at the time the region was so sparsely populated. future events of that magnitude will probably cause great damage to large sections of whichever city is closest to the epicenter. Memphis and St. Louis are prime examples of potential disastrous events.

It's not a matter of "if" another 8 magnitude quake will strike the New Madrid fault, it's a matter of "when." The "where" is also important but no matter when or where that event happens there are a few common-sense preparations which may save lives or prevent injuries.

  • If you are able, get outside and away from buildings where danger of falling debris is a threat.
  • If you can't get outside, get into a doorway or under some structure which might protect you from falling objects.
  • Avoid downed power lines after a quake. If possible, don't use bridges until inspections can be made.
  • Fire is the most common earthquake related hazard due to downed power lines or broken gas lines. Fire alarms and sprinklers may be activated by the quake even without the presence of fire.
  • Be alert for "aftershocks" which are common after a large earthquake.
  • After the shaking stops, make certain you aren't injured. You can't help others until and unless you're OK yourself.
Disaster Supply Kit

It's a good idea to maintain a "Disaster Supply Kit" and have it ready at all times.
Some of the items each kit should contain are:

  1. A first aid kit
  1. Bottled water
  1. Sturdy shoes for each family member
  1. Flashlights
  1. Batteries
  1. A cell phone
  1. A battery powered radio
  1. If possible, store at least a three-day supply of non-perishable food. Select foods that require no refrigeration, preparation or cooking, and little or no water.