LITTLE ROCK, Ark. A previously unknown fault in eastern Arkansas could trigger a magnitude 7 earthquake with an epicenter near a major natural gas pipeline, a scientist said Wednesday. Haydar Al-Shukri, the director of the Arkansas Earthquake Center at the University of Arkansas at Little Rock, said the fault is separate from the New Madrid fault responsible for a series of quakes in 1811-12 that caused the Mississippi River to flow backward.

Acres of cotton fields cover the fault west of Marianna, about 100 miles east of 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.