In today’s society,
Arkansans think of thunderstorms, floods, and tornadoes as devastating natural
disasters, but the Natural State also has the threat of earthquakes to remember. Most earthquakes are gentle
reminders of activity beneath the surface, but in the Northeast part of the
state down the Mississippi Alluvial Plain lies the southern portion of the New
Madrid Seismic Zone (NMSZ).
Residents living in
the NMSZ are not the only citizens that should be preparing for an earthquake. As shown on the map above, small
earthquakes occur across the state. Due to the soil composition of Northeast and Eastern
Arkansas the effects and damages from a large magnitude earthquake
would be felt for miles.
Three great earthquakes occurred on December 16, 1811 on the southern branch of
the fault in eastern Arkansas. The first earthquake which measured magnitude 8.6 occurred at 2:30 am; the
second, which was magnitude 8.3 at 8:15 am; and the third, which was magnitude
8.0, at noon. These three earthquakes ruptured the entire southern segment of
the New Madrid fault, a length of about 90 miles.
On January 23, 1812, an
earthquake of magnitude 8.4 ruptured the central segment of the fault, a length
of about 45 miles. The largest of the earthquakes, which was a magnitude 8.8,
occurred on February 7, 1812, near the town of New Madrid, Missouri. It ruptured the entire northern branch of the fault, a length of about 60
miles. More than 200 additional moderate earthquakes occurred on the New Madrid
fault between December 16, 1811, and March 15, 1812.
There were also about
1,800 earthquakes with body-wave values of about 3.0 to 4.5. Eighteen of the
earthquakes were felt as far away as Washington, D.C.
Since 1812, only two large
earthquakes of magnitudes greater than 6.0 have occurred in the New Madrid fault
zone. The first struck January 4, 1843, centered in Arkansas at the extreme southern end of the fault, at Marked Tree,
Arkansas. It had a magnitude of approximately 6.3. The second large, historic
earthquake (magnitude of approximately 6.7) with an epicenter at the northern
end of the fault (Charleston, Missouri), occurred October 31, 1895.
Nuttli, 0tto. W.(1973).
The Mississippi Valley Earthquakes of 1811 and 1812: Intensities, Ground Motion and Magnitudes,
Bulletin of the Seismological
Society of
America. Vol. 63, No. 1, pp. 227-248 February 1973