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 So just what is The 7.9 Scenario and what does
it mean?
See the details in my FAQs,
or read the summary below.
The 7.9 Scenario is the imagining
of what it would be like if a magnitude 7.9 earthquake struck
on the New Madrid Fault at the same epicenter as the December
16, 1811 earthquake.
These imaginings are turned into
solid estimates of the damage, both to property and to lives,
by cross-multiplying the expected shaking intensity map with
the population density of the region as determined from the United
States census. This gives some indication of the amount of destruction
that could be expected from such an event.
In addition, using the economic
census and the shaking intensity map, one can estimate the total
impact on the economy of the region, and by implication, the
impact on the economy of the United States.
The 7.9 Scenario is a worst-case
scenario because it assumes all the worst things that can happen
do happen. The probability is that the next big earthquake on
the New Madrid will be of a lesser intensity, and therefore,
inflict less damage to the region. However, there have been even
bigger earthquakes in the region, so one should not become complacent.
The probability that the Mississippi
will be at flood stage when the earthquake hits is low, but what
if it follows Murphy's law and occurs at the worst possible moment?
The probability that the shaking of the Kentucky dam will destroy
the locks may be low; it needs to be studied further. The probability
that the shaking will be enough to break the levees in New Orleans
may be low, but are we really sure. Will the Old River Control
Structure survive the shaking? I am not sure, but it has already
almost been lost when only plagued by the high waters of the
mighty river.
So just how worst case is The
7.9 Scenario. I am not sure, but it does give some indication
of the kind of world we can expect when the next giant earthquakes
tears apart the central United States. It is enough of a warning
to make me worry and to think we should start doing more planning
and preparation for what might occur. The odds are low, but the
risk is far too great to ignore.
Now, go read my Frequently
Asked Questions.
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