Fault line underneath Arkansas continues ominous rumblings

Wednesday, December 21, 2011

Two hundred years ago Dec. 16, the New Madrid Seismic Zone unleashed one of the most powerful earthquakes to shake the lower 48 states -- a quake so powerful it caused waterfalls on the Mississippi River, shook houses in Charleston. S.C., and rang church bells in Boston.

The first terrifying jolt hit at 2:15 a.m., with modern estimates pinning it at 7.7 on the Richter scale. Six hours later came what is now known as the Daylight Shock, a quake of similar intensity.

Nor was the New Madrid finished. It produced a 7.5-magnitude temblor on Jan. 23, 1812, and another 7.7 quake on Feb. 7, 1812. The USGS notes that some other sources have calculated the power of the Feb. 7 quake at 8.8, a measurement that would make it the second most powerful quake to hit the 48 contiguous states and the third largest ever among the 50 states.

The New Madrid continues to rumble, but somewhat more gently. Between Dec. 7 and Dec. 12 of this year, USGS recorded six small quakes ranging from 1.0 on the Richter scale near Ridgely and Tiptonville, Tenn., to a 2.4-magnitude quake about 1 mile west-southwest of Blytheville. Arkansas has also experienced a large swarm of quakes around Greenbrier and Guy in north-central Arkansas, one as large as magnitude 4.7.

"If the Mid-South had been as populated in 1811-12 as it is now, the destruction from that Dec. 16 quake would have been incalculable," said Deborah Tootle, associate professor for community and economic development for the University of Arkansas Division of Agriculture. "And while nothing of that magnitude has shaken Arkansas in this century, we still have enough seismic activity to remind us that we need to be prepared."

The University of Arkansas Division of Agriculture has fact sheets available for download to give individuals and families some guidelines on preparing and coping with quake damage. They include:

The "Be Aware and Prepare" series of disaster preparation fact sheets. The earthquake sheet may be found online at www.uaex.edu/news/pressroom/storm_recovery/BeAware_Earthquakes.pdf.

"Earthquake Preparedness," www.uaex.edu/Other_Areas/publications/PDF/FSA-9600.pdf.

"Earthquake Survival," www.aragriculture.org/disaster/earthquakes/earthquake_survival.pdf.

Quake-ready Arkansans should also become familiar with the latest recommendations for safety that include remaining in the house and practicing "Drop, Cover and Hold On," and compiling a kit with food, water and other essentials to enable an individual and family to survive for 72 hours.

"The new recommendations reflect studies that show running outside in the street makes one vulnerable to collapsing buildings, trees, power poles and other dangers," Tootle said.

Learn more about "Drop, Cover and Hold On" at earthquakecountry.info/dropcoverholdon/.

The New Madrid came back into the public eye in 1989, when the late Iben Browning, a climatologist, projected a 50 percent chance for a magnitude 6.5 to 7.5 earthquake in the New Madrid seismic zone around Dec. 1-5, 1990. While his prediction was not taken seriously by seismologists, publicity about it prompted many government agencies to review preparedness, building codes and conduct safety drills.

For a list of the most powerful quakes in U.S. history, visit earthquake.usgs.gov/earthquakes/states/10_largest_us.php.

For more information on emergency preparedness and recovery, see the Disaster Response Handbook online at www.aragriculture.org/disaster/, or contact your county extension office.

Respond to this story

Posting a comment requires free registration: