Jefferson County - East-West Gateway Coordinating Council

A Regional Overview All-Hazard Mitigation Plan 53
St. Louis, Missouri, and Memphis, Tennessee. A repeat today of the earthquakes of 1811-
12 would cause widespread loss of life and billions of dollars in property damage. The
potential for the recurrence of such earthquakes and their impact today on densely
populated cities in and around the seismic zone has generated much research devoted to
understanding earthquakes. By closely monitoring the earthquake activity, scientists can
hope to understand their causes, recurrence rates, ground motion and disaster mitigation.
Earthquakes pose a serious threat to many Missouri communities. Local governments,
planners, and engineers must consider the threat as they seek to balance development and
risk. Identifying locations susceptible to seismic activity generated by nearby faults,
adopting strong policies and implementing measures and using other mitigation
techniques are essential to reducing risk from seismic hazards in the East-West Gateway
Coordinating Council planning region.
Based on the January 2003 estimates, Jefferson County is at most risk for Modified Mercalli
Level VII (7.6 level) as likely adverse impacts. However, due to the geologic setting in
Jefferson County in terms of alluvial soils along the Missouri River, Level VIII should be used
for planning purposes. The possible effects at Level VIII are shown below.
Without Mitigation Measures
Life Critical
Property Critical
Emotional Critical
Financial Critical
Comments Jefferson County is considered a high-risk area for damages from an
earthquake as a result of the population density, condition of existing buildings and
infrastructure and the geologic setting.
With Mitigation Measures
Life Limited
Property Limited
Emotional Critical
Financial Limited
Comments With mitigation measures in place, this will assist with current and future
construction. Older masonry buildings will still be at risk.
Landslide, Sinkhole and Underground Mine Collapse Mitigation Measures
The next disaster’s likely adverse impact on Jefferson County could be limited to negligible
in terms of amount of damage to infrastructure (utilities, communications) buildings,
deaths and other cascading disasters including fire and explosions from natural gas and oil
pipeline ruptures. These types of hazards occur on a much smaller scale than do
earthquakes. The affected area may include one or two homes in a subdivision that have
been constructed on a failing hillside, or on the side of a sinkhole or mine tunnel. Clearly,
there are mitigation measures that can be taken to reduce or eliminate the risk of future