Re: What is the probability of an Earthquake effecting Russell County, Ky

I am going to break your question down into several related questions and 
answer each one:

Where do earthquakes occur in the mid-continent?

The New Madrid zone is the best known location for earthquakes, but not the 
only one by any means.  Look at the maps at:  http://www.eas.slu.edu/Earthquake_Center/SEISMICITY/newmadrid1975-1995.html 
to see earthquake locations for a twenty year period.  The New Madrid fault 
is the most active structure, but there are active faults both east and 
west of the New Madrid zone, including one cluster of earthquakes in 
western Ky.  

Which of these faults could affect areas in Ky?

Any of the faults in the maps at the link above could produce earthquakes 
that are big enough to be felt in Ky.

What are the likely effects of quakes on these faults?

That depends on the size of the quake that occurs.  Many of the quakes 
shown on the maps at the link above are relatively small and probably only 
caused enough shaking to be felt by some people.  The 1811-1812 earthquakes 
on the other hand, were very large (Richter magnitude 8+) and caused damage 
over a 
wide area.  See the Figures in this paper:  http://www.eas.slu.edu/Earthquake_Center/SEISMICITY/Street/rstreet.html  
These maps show the Modified Mercali Intensity (a measure of how hard the 
area shook - this depends on quake size, distance from quake, and local 
ground conditions).  A review of these maps suggests that Kentucky would 
experience Mercalli Intensities of V-VII (5 to 7).  This would involve 
cracked plaster and masonry walls to possible collapse of poorly built 
masonry walls or chimneys.  See  http://www.eas.slu.edu/Earthquake_Center/mercalli.html
for an explanation of the Mercalli Scale.

All of these maps and charts are from the Earthquake Center at the 
University of St Louis.  The USGS web site also has information:   http://www.usgs.gov and the Regional Center for the central US is at the 
University of Memphis, which has a good page on New Madrid  http://www.ceri.memphis.edu/public/facts_short.shtml

The final question is how likely is an earthquake?

This depends on two things, how big a quake you are talking about, and how 
long you are willing to wait.  The longer the time, the more likely there 
is to be a quake during that time.  The bigger the quake, the less likely 
it is to happen during a given time.  At the U of Memphis site, you can see 
probabilities for the New Madrid fault for different magnitudes and time 
periods.  For magnitude 6.3 (which would cause moderate local damage, near 
the fault) they estimate a 40 to 63% Probabilty of a 6.3 quake within the 
next 15 years and an 86-97% chance within the next 50 years.  That means a 
moderate earthquake is virtually certain within the next 50 years.  For a 
really big quake (magnitude 8.3), the likelyhood is much lower, only 0.3 to 
1.0% in the next 15 years and 2.7 to 4.0% in the next 50 years  In other 
words, you have less than a one in twenty chance of having a major quake in 
this area in your lifetime.

The prediction of earthquakes is a difficult business and anyone who makes 
a definite prediciton that there will be a quake at a certain time is a 
charlatan.  The only thing that can currently be predicted is the relative 
level of risk.  Even with the very low odds outlined above, a major New 
Madrid quake could occur tomorrow, or next week, or next month, or it might 
not occur for 500 years, no one can say with what we know today.  Because 
of this, it pays to be prepared.  Given where you live, you should take 
some simple precautions.  Get the water heater in your house strapped to 
the wall with metal straps that are securely fastened into wall studs.  
Bolt tall bookcases and cabinets into studs to keep them from falling over. 
 Do not hang heavy pictures, mirrors, etc over beds (the one fatality in a 
recent earthquake in CA was from falling objects landing on the head 
of someone lying in bed).  If you have propane or natural gas, know where 
the shut off valve is, how to use it, and keep a wrench hanging near the 
valve so that you can quickly shut it off in event of a leak.  Keep a 3-day 
supply of water, food that doesn't need refrigeration or cooking, and 
medicines in your house.  Keep this supply up-to-date and keep a first-aid 
kit with it.  Also keep a radio, flashlight, and spare batteries for both. 
 Many of these things are good ideas to have around even if you don't live 
in earthquake prone areas.

The bottom line:  You are unlikely to experience significant damage where 
you live during your lifetime, but the impact of a major quake could be 
severe and so you should be prepared.  By the way, before I moved east, I 
lived near San Jose, CA and experienced the 1989 Loma Prieta 
(World Series) earthquake firsthand, but we had no damage, thanks to our 
preparation.

David Smith
La Salle University, Philadlephia, PA (Where we have had at least 3 quakes 
big enough to be felt in the past 10 years)