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Kentucky Geological Survey Statement on the New Madrid Seismic Zone

The New Madrid Seismic Zone is again in the news because of a recent paper, "The New Madrid Seismic Zone: Not Dead Yet." This study has been widely reported and draws attention to the New Madrid Seismic Zone. The Kentucky Geological Survey and the UK Department of Earth and Environmental Sciences has studied the seismic zone for decades and operates a network of seismographs in this zone, including the Central U.S. Seismic Observatory just a few miles from the town of New Madrid, Mo. Monitoring seismic activity on the New Madrid Seismic Zone has been under way at UK for more than 30 years. A couple of dozen small earthquakes are recorded by the Kentucky Seismic and Strong-Motion Network each year. Seismologists generally agree that the zone is indeed active. Ongoing seismicity there and the presence of an active fault that changed the course of Mississippi River and dammed Reelfoot Lake in 1811-12 is evidence of this activity. Thus, whether the zone is active or not is not a question that the media and citizens need to ask. The questions they need to ask are:

1. How often are large damaging earthquakes expected to occur in the New Madrid Seismic Zone, and how large could they be? If one does occur, what will the level of ground shaking be at any given distance from the epicenter for important structures? Scientific analysis of the region indicates large damaging earthquakes, from magnitude 7 to 8, occur every 500 to few thousand years. The 1811-12 earthquakes occurred 200 years ago. KGS Report of Investigations 22 (2010), "Ground Motion for the Maximum Credible Earthquake in Kentucky," gives many of the important seismic factors needed for planning and construction. KGS RI 22 is available at http://kgs.uky.edu/kgsweb/pubs/moreinfo.asp?titleInput=17471&map=0.
2. What reasonable steps should communities take to mitigate hazards and reduce risks to the public? The Kentucky Geological Survey recommends mitigation measures appropriate for the actual risk, such as proper design and construction of buildings and infrastructure, to prevent disaster in case of a major New Madrid quake.

Earthquakes are a natural phenomenon. Although seismologists and geologists can calculate patterns for recurring seismic activity, locate the zones of activity, measure how energy is transmitted through rock, and determine how shaking of the earth would result, human knowledge is limited, and we do not have the ability to precisely predict future earthquakes. The Kentucky Geological Survey provides scientifically based information about Kentucky’s seismic hazards. Real-time recordings from some of stations can be viewed online at http://www.uky.edu/KGS/geologichazards/equake3.htm.