Overview

In the past 25 years, scientists have learned that strong earthquakes in the central Mississippi Valley are not freak events but have occurred repeatedly in the geologic past. The area of major earthquake activity also has frequent minor shocks and is known as the New Madrid Seismic Zone. The NMSZ is made up of several thrust faults that stretch from Marked Tree, Arkansas to Cairo, Illinois.

Earthquakes in the central or eastern United States affect much larger areas than earthquakes of similar magnitude in the western United States. For example, the San Francisco, California, earthquake of 1906 (magnitude 7.8) was felt 350 miles away in the middle of Nevada, whereas the New Madrid earthquake of December 1811 rang church bells in Boston, Massachusetts, 1,000 miles away. Differences in geology east and west of the Rocky Mountains cause this strong contrast.
New Madrid Seismic Zone. Central United States Earthquake Consortium.

Recent studies have indicated that the New Madrid Seismic Zone is not the only 'hot spot' for earthquakes in the Central United States. On June 18, 2002, a 5.0 magnitude earthquake struck Evansville, Indiana with an epicenter between Mt. Vernon and West Franklin in Posey County, in an area that is part of the Wabash Valley Seismic Zone. According to the Indiana University Indiana Geological Survey, while there was minor damage associated with the earthquake, the tremor was a warning to residents of the Wabash Valley Seismic Zone that earthquakes can, and do, strike close to home.

The Wabash Valley Seismic Zone is located in Southeastern Illinois and Southwestern Indiana and it is capable of producing 'New Madrid' size earthquake events. Since the discovery of this seismic zone, earthquake awareness and preparedness have increased. Residents are seeing that moderate sized earthquakes are not just occurring to the south, but occur right at home and can affect Illinois, Indiana, and Kentucky. Geologists in Indiana and Illinois have found liquefaction sites and sand dikes that shows the evidence of prehistoric earthquakes in the region. By examining the size of the dikes and sediment found within the sand dikes, geologists are able to estimate the size of the earthquake it took to create the formations.
Wabash Valley Seismic Zone. Central United States Earthquake Consortium.

Earthquake Hazard Information - USGS Publications

Earthquake scenarios for your drill

Earthquake information is available from the organizations below, as well as for each state:

Organizational Resources

Central U.S. Earthquake Consortium

USGS Central & Eastern U.S. Earthquake Hazards Webpage

Center for Earthquake Research and Information, University of Memphis

Center for Community Earthquake Preparedness, University of Mississippi

Multidisciplinary Center for Earthquake Engineering Research

Saint Louis University

University of Arkansas at Little Rock

Central US ShakeOut Drop, Cover, and Hold On Video, which features a "Drop, Cover, and Hold On" drill in action and talks about why this is the recommended method for protecting yourself during an earthquake:

Why is it important to do a Drop, Cover, and Hold On drill? To react quickly you must practice often. You may only have seconds to protect yourself in an earthquake, before strong shaking knocks you down--or drops something on you. Practicing helps you be ready to respond.

• If you are inside a building, move no more than a few steps, then Drop, Cover and Hold On:
  • DROP to the ground (before the earthquake drops you!),
  • Take COVER by getting under a sturdy desk or table, and
  • HOLD ON to it until the shaking stops.
  Stay indoors till the shaking stops and you are sure it is safe to exit. In most buildings in the U.S. you are safer if you stay where you are until the shaking stops.


• If you are outdoors when the shaking starts, you should find a clear spot away from buildings, trees, streetlights, and power lines, then Drop, Cover and Hold On. Stay there until the shaking stops.


• If you are driving, pull over to a clear location, stop and stay there with your seatbelt fastened until the shaking stops. Once the shaking stops, proceed with caution and avoid bridges or ramps that might have been damaged.

Ground shaking during an earthquake is seldom the cause of injury. Most earthquake-related injuries and deaths are caused by collapsing walls and roofs, flying glass and falling objects. It is extremely important for a person to move as little as possible to reach the place of safety he or she has identified because most injuries occur when people try to move more than a short distance during the shaking.

Look around you now, before an earthquake. Identify safe places such as under a sturdy piece of furniture or against an interior wall in your home, office or school so that when the shaking starts you can respond quickly. An immediate response to move to the safe place can save lives. And that safe place should be within a few steps to avoid injury from flying debris.

Further information:

Drop, Cover, and Hold On!