NEW TAKES ON HISTORIC QUAKES ILLINOIS
INDIANA
Two centuries on,
scientists revisit
the magnitudes
of New Madrid’s
biggest rumbles
By Sid Perkins
MISSOURI
NEW MADRID
KENTUCKY
1812
1812
NEW MADRID
SEISMIC ZONE
1811
TENNESSEE
ARKANSAS
MISSISSIPPI
In the autumn of 1811, the United States was barely 35 years old. The fledgling nation included only 17 states, all east of the Mississippi
River, but it boasted a lot of new territory thanks to the Louisiana Purchase
of 1803. Neither the buyers nor the
sellers knew that the recent addition’s
basement contained a seismic time
bomb nearly ready to go off.
At around 2: 15 a.m. on December 16,
1811, a series of massive earthquake pummeled what is now southeastern Missouri
and northeastern Arkansas with ground
motions so strong that trees snapped in
two as they whipped back and forth. The
landscape rose several meters in some
areas and sank in others, changing the
courses of creeks and waterways. During
one of the quakes, even the mighty Mississippi was diverted; portions near the
quake’s presumed epicenter flowed backward for at least several hours, and possibly a day or more. People felt the temblor
as far away as New York state, and seismic vibes from an aftershock that struck
at dawn traveled almost as far, reaching
residents in Georgia and what would
soon become the state of Louisiana.
Another quake of a similar size — maybe
an aftershock, or maybe a separate quake
along a different portion of the same fault
zone — rumbled on January 23, 1812. The
final major shaking in the series came
about two weeks later, on February 7,
when spreading seismic waves flung
books from their shelves in Charleston, S.C., and rattled cups and saucers in
Washington, D. C.
Scientists long considered these
quakes along the New Madrid Seismic
Zone—a zigzag-shaped set of faults
ALABAMA
1974–2002 Before 1974
New Madrid quakes
SOURCE: USGS
named for the small town in Missouri
near where the quakes were felt most
powerfully — to be some of the strongest
ever on the North American continent.
After all, some scientists estimate that the
area violently shaken by the three most
energetic quakes was two to three times
as large as that experiencing comparable
ground motions from the magnitude
9. 2 quake that slammed southern Alaska
in 1964, and about 10 times the area similarly affected by the magnitude 7. 8 quake
that wrecked San Francisco in 1906.
As recently as the late 1970s, scientists
estimated that the strongest of the New
Madrid quakes may have been magnitude 8.75. But in the last decade or so,
researchers have proposed that the New
Madrid quakes were smaller, possibly
much smaller. Debate about the size of
these quakes rages in journal papers and
QUAKE POINTS: USGS, BACKGROUND: GEOATLAS/GRAPH-OGRE, ADAPTED BY JANEL KILE Y,
PICTURES: USGS PHOTOGRAPHIC LIBRARY
www.sciencenews.org
