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Press Article: April 11, 2004
What Happens In Sikeston
When A Giant Earthquake Strikes?
The city of Sikeston rests atop
the mid-section of the New Madrid Fault. Most residents know
that earthquakes ravaged this area 193 years ago, and they remember
when a repeat was predicted 14 years ago - but nothing happened.
The failure of that prediction did not change the chances for
another earthquake - it is still inevitable. There remains the
need to consider what will happen when, not if, the New Madrid
fractures again.
Sam Penny, a traveling author
and lecturer, recently published his novel Memphis 7.9, a science-based
story of a 7.9 magnitude earthquake that strikes within a few
miles of Memphis, a major metropolitan area in the central United
States. Here, after providing some background on the fault, he
spins a fictional tale about what Sikeston might look like after
"the big one."
Memphis, Tennessee, rests on
the flood plains and bluffs overlooking the Mississippi River,
forty-five miles from the southern half of the New Madrid Fault.
Shelby County holds over a million residents.
Sikeston, Missouri, sits atop
the almost imperceptible Sikeston Ridge the same distance from
the northern end of that section, but directly over a portion
of the thrust fault section of the seismic zone. The center of
town is twenty-five feet higher in elevation than surrounding
communities built on the remains of the old bayous and river
channels.
The 350-mile long New Madrid
Seismic Zone running from east central Arkansas to southern Illinois
hides beneath a half-mile-thick layer of mud and sand, sediments
that fill the Mississippi valley from Illinois to Louisiana.
Apart from white circles of sand outlining old sand boils, you
can find little evidence of the great earthquakes that rocked
that region in 1811 and 1812. Five of those temblors measured
over 8.0 in magnitude. The aftershocks continued for five years.
That episode remains the largest seismic event to strike the
United States in recorded history.
The 200 or so minor earthquakes
that occur in the New Madrid Seismic Zone each year are mostly
unfelt, and the few that are noticed are of little danger, doing
nothing more than rattling the nerves. What people fear most
is a great earthquake, one whose magnitude is 7.4 or more. On
the New Madrid there has not been a great earthquake since the
1812.
The USGS says the chances are
one in ten that people alive today will experience or hear of
a giant New Madrid earthquake within his or her lifetime, but
no one knows exactly when. Chances for a major earthquake in
the 6.0 to 7.0 magnitude range are two in three, odds you can
bet on.
A great earthquake on the southern
extension would result from a long fracture along the fault in
the earth's crust. The book Memphis 7.9 is based on what happens
when the southern extension of the fault fractures along a trace
over seventy miles long, the size necessary for a 7.9 magnitude
event. The epicenter, the surface point above where the fracture
starts, is at the Arkansas-Missouri border under Interstate-55.
The most violent shaking often
occurs near the end of the fracture furthest away from the epicenter.
Crustal fractures propagate close to the speed of the shear or
S-waves, and these waves build up into a burst, like the sonic
boom of a jet fighter approaching the speed of sound. Structures
along or near the trace of the fracture are hit with the accumulated
energy in a terrific bang rather than a roar spread out over
a longer period of time. Ridgely, Tennessee, 35 miles south of
Sikeston at the northern end of the fracture would literally
be blown apart by a violent eight-second burst of seismic energy.
In the book it takes twenty-three
seconds for the seventy-mile long fracture to happen. Places
near the fault are subjected to at least fifty-five seconds of
violent shaking, longer if there are reflections from major geological
structures like the mantle and nearby faults. The longer the
shaking the greater the damage done, so longer fractures produce
higher magnitudes and greater damage.
The following description of
Sikeston is fiction. It is the author's perception of what it
would be like here at that point in time. This story is not in
the book simply because it already had too many characters and
events. This is a tale about you.
You are walking past the Sikeston
Depot when you hear the rumble of the P-waves. It is seventeen
seconds after the start of the fracture sixty-five miles away.
Animals are the first to react. Birds fly upward, cats climb
the curtains, dogs begin their incessant barking. The old drifter
sitting on the park bench feels a vibration akin to a teenager's
boom box beating up from the ground. People in quiet zones, like
the librarian in the Sikeston Public Library, hear the rumble,
but shoppers in the grocery store and the children running and
screaming on the schoolyard are slow to notice.
After six seconds the roar builds
as P-waves reflected from the earth's mantle sixty miles below
the surface add their energy to the chorus. This sound is enough
to get most everyone's attention, and people look around, wondering
what is going on. Is it a fighter jet showing off at low altitude?
Had a train derailed? A very few realize the significance of
what they hear and head for safety, either diving under their
desks or running somewhere out of doors away from trees, electrical
power lines, and the facades of old brick buildings.
Eighteen seconds after the start
of the P-wave ensemble, the pavement, grass, floor, wherever
you have your feet, begins to shake, back and forth, harder and
harder. Within five seconds the shaking builds to an intensity
level of VIII on the Modified Mercalli Intensity Scale used by
seismologist to measure such things. The collapse of ordinary
substantial buildings begins; poorly built structures are already
crumbling to the ground. Chimneys, columns, brick fences, block
walls all start to shake apart under the force of accelerating
at a quarter of the force of gravity, falling down on cars and
bushes and people who happen to be in the way.
Inside homes and offices even
the heavy furniture is being thrown around, and any hot water
tanks not tied to the wall rip out, pulling their gas lines lose
and starting the first of the many fires that will plague the
city.
The intensity level builds to
IX as the acceleration forces reach half that of gravity and
then beyond. The intensity climbs halfway to X. In some places
the constructive interference of the seismic waves may be enough
to toss objects into the air. Major buildings shake apart and
fall, their roofs caving in on top of whatever or whoever is
below. Power poles break and lines snap back and forth, arcing
and cutting the wires which fall to the ground to writhe about
like snakes, at least while there is still electrical power coursing
through them. Trees tangle their limbs and pull each other to
the ground.
By now the Love and Rayleigh
waves are rolling in. The first wave slithers the ground from
side to side and the second rolls the ground up like an ocean
wave, maybe only a couple of feet high, but enough for people
whose eyes remain open to see.
The violent shaking continues
unabated for forty seconds. Then it lessens, but only slightly.
By now much of the major damage is done. Finally, seventy-five
seconds after the shaking first started the earth quiets. The
silence is deafening, until the screams of the injured and frightened
pierce the ringing in your ears.
Your heart is pounding and your
breaths come in gasps. The adrenaline coursing through your body
is enough to throw your body into shock if you let it. You take
a deep breath and let it out. Then the first little aftershock
shakes the ground, only for a second, but enough to spike your
blood pressure to even higher highs. If you are a heart patient,
now is the time for that attack.
Looking around you can see a
number of columns of black smoke, homes and businesses burning,
but you hear no sirens. Down the street you see the firehouse
has fallen in on the equipment, and the firemen are trying to
uncover it. There is a crowd helping and screaming for the firemen
to come help save their own homes, but the firemen cannot respond.
People begin to venture into
half-fallen buildings, some with teetering brick walls just waiting
for the next shake to bring them down. These hardy souls try
to pull victims from the buildings before another fire breaks
out or the walls fall further. Unless they are careful, they
will become victims themselves. Injured are laid in rows in the
street, away from danger. Some are dying; others have already
died.
Cars are mostly stopped on the
streets, though some of the bigger SUVs are trying to climb over
the fallen telephone poles to get to some place important, maybe
to where they left their children in school.
You remember your father working
at the shop east of downtown. You run down the middle of the
street, dodging debris, jumping over fallen poles and lines.
Along the way you see some bigger buildings that seem to have
sunk into the ground, tilting them to the side. The ground and
pavement seem wet, like there has been a recent rain. Liquefaction
turned some of the lands into quicksand, then when the shaking
stopped, the sand and dirt settled back into its normal state.
As you approach the shop, you
see water ahead where the old creek used to be, down by the Elks
Lodge. Now you notice mounds of white sand in an open field,
some with small streams of water flowing out the top. Only then
do you realize the smell that pervades the air. It is awful,
like someone has dropped a crate load of rotten eggs, or stirred
an open septic tank. You retch, but it does no good.
You find your father sitting
on the ground next to the fallen shop. He seems dazed. You sit
down beside him and reach out to hug him. He is crying; so are
you.
Earthquakes do little to change
the earth's landscape. The hills and plains have felt earthquakes
since their beginnings and are largely in a state of relaxation
towards the shaking. Earthquakes do their greatest damage to
man-made structures, for those are built to defy gravity and
press against the environment. The constructs of our society
will break, and the more violently the earth shakes, the greater
will be the destruction of what man has built. Our society should
plan for a great earthquake to happen - someday it will. If we
build right we can mitigate the damage, but we can never stop
the earthquake from happening.
The story of Sikeston is not
over after shaking from the giant earthquake ends. Aftershocks,
some that could be as large as the first, will continue to pound
the New Madrid Seismic Zone for months, if not years. The levees
lining the Mississippi River are mostly destroyed. If the River
is at flood stage, water will immediately flow out across the
lands and Sikeston Ridge may become an island for a time, home
for twenty thousand folks from the surrounding lands. If the
River is not at flood stage, the floods will be delayed, but
there is no way for the levees to be replaced in time to prevent
the water from coming.
People in Sikeston must care
for themselves for an extended period of time. Everyone within
two hundred miles has suffered mightily in the same earthquake,
and all their energies will be focused on helping themselves.
In time the military might arrive with water and food, but in
the meantime people must find their owns way to subsist.
Sikeston residents are lucky.
Once some of the roads are cleared they may be able to head west
or north and find help, at least find safe haven away from the
floods. The people in Memphis are cut off, and there you will
find a million souls trying to subsist.
The story will continue for years.
The economy of the United States may be severely stricken. And
the chances are one in ten that you may be alive to see this
happen. So are you going to do something about planning for how
to survive? Or are you going to be like so many and say, "Aw,
it'll never happen. Why worry."
Contingency and mitigation planning
are vital - planning may save your life when the inevitable happens
and a great earthquake does strike. |
