QUAKE (cont.)
ation of St. Francis Lake.”
Six hours after the main quake, just as dawn was breaking, a massive aftershock struck. This new earthquake was centered just northwest of what is now Marked Tree in Poinsett County and had an estimated strength of 7.0. A chain reaction of hundreds of other aftershocks followed. Forty-nine aftershocks were recorded just in northwestern Crittenden County, ranging from Magnitude 4.7 to 6.8.
The New Madrid is one of the most well-known major faultlines. Faultlines are caused by a crack in the Earth, known as an intraplate fault line, where tremendous pressures build up over time. The pressures are released by earthquakes, usually occurring miles beneath the surface.
The fault line runs from Poinsett County across to Mississippi County to New Madrid, roughly parallel to the Missouri-Tennessee-Kentucky border on the Mississippi River.
In 1815, Congress passed the New Madrid Act. As part of an early federal effort to help victims of natural disasters rebuild their lives, Congress offered new federal lands to allow the settlers to rebuild their broken lives.
Accepting these New Madrid Certificates, as they were called, thousands of people moved from the area, mostly deeper into areas of Arkansas and Missouri. The aftereffects of the New Madrid quakes actually led to the increased population of Arkansas in the years before it was established as a territory. There have been many earthquakes in the region since the disasters of 1811 and 1812. In 1843, a Magnitude 6.2 quake occurred in Poinsett County. A Magnitude 5.0 quake occurred in Mississippi County in 1878. Three magnitude 4 earthquakes were recorded in eastern Lawrence County in 1918. An earthquake measuring 5.0 on the Richter scale occurred between Trumann and Marked Tree in Poinsett County in March 1976, causing power outages and broken windows across Jonesboro and as far away as Paragould, nearly 40 miles away.
Earthquakes have been detected far from northeast Arkansas. In fact, most counties in Arkansas have experienced earthquakes, though most are so subtle or centered so far below the surface that they are never noticed.
However, a sizable tremblor of 4.7 was recorded in Cleveland County in 1911.
Quakes greater than Magnitude 4.0 were recorded near Malvern in 1930 and El Dorado in 1939. A quake of magnitude 4.5 was recorded in Pulaski County in 1969. Two quakes of similar strength were felt in Clark County in 1974. A series of earthquakes occurred near Enola, just north of Conway, in Faulkner County in January 1982.
Hundreds of quakes under Magnitude 2.0 were recorded in the weeks that followed, called the “Enola Swarm” by geologists. The highest was 4.5, but no major damage or injuries were reported. A Magnitude 4.7 quake was recorded in 2011.
“Dozens of earthquakes are recorded across Arkansas each year,” said Bridges.
“Fortunately, most cause no damage or are even noticed. The New Madrid quakes are still the worst quakes recorded east of the Rocky Mountains.
Geologists rate the area along the New Madrid Fault at high risk for another major quake in the next 50 years.”
A major quake in the region would no doubt cause much more damage and have a much greater potential loss of life now after more than 200 years of popluation growth and development.
“With planning and careful attention to surroundings and warnings, the danger can be reduced,” said Bridges, “but these earthquakes remind us that the power of nature is not to be underestimated.”
