The fault is separate from the New Madrid fault responsible for a series of quakes in 1811 to 12 that caused the Mississippi River to flow backward, said Haydar Al-Shukri, the director of the Arkansas Earthquake Center at the University of Arkansas at Little Rock.
(Related story: "Midwest Faces Quake Danger From Shifting Fault, Experts Say" [May 10, 2007].)
Acres of cotton fields cover the newfound fault west of Marianna, about 100 miles (161 kilometers) east of Arkansas's capital, Little Rock.
But stretches of fine sand mixed with fertile soil gave away the fault's location, Al-Shukri said.
Liquefied sand bubbled up through cracks in the earth, while ground radar and digs showed vents that let the sand reach the surface, he said.
The fault, likely created in the last 5,000 years, sparked at least one magnitude 7 earthquake in its history. Such temblors cause massive destruction in their wake.
"This is a very, very dangerous [area] at risk of earthquake," Al-Shukri said. "When you talk about [magnitude] 7 and plus, this is going to be a major disaster."
"Pipes All Over the Place"
Al-Shukri has said a gas pipeline crossed the newly discovered fault, but declined to name the company that owned the pipeline.
A map made by the Arkansas Public Service Commission shows an Arkla Energy Resources gas pipeline in the area.
Rebecca Virden, a spokesperson for CenterPoint Energy Inc., which owns Arkla, said Wednesday that the company worked closely with public officials to prepare response plans for earthquakes and other natural disasters.
Pipes are "all over the place," Virden said. "We, CenterPoint Energy, or someone else has a pipeline everywhere."
Clint Stephens, chief of pipeline safety at the public service commission, said the federal government would oversee any interstate lines. The U.S. Department of Transportation's Office of Pipeline Safety did not immediately respond to a request for comment.