LITTLE ROCK, Ark. - Jobelle Johnston of Jonesboro, Ark., says she doesn't live in constant fear of a major earthquake on the New Madrid fault line. But she doesn't ignore the warnings, either. "I think it's prudent to be cautious," said Ms. Johnston, a schoolteacher who was recently looking for heavy wire to bolt her china cabinet to the wall in case of a quake. "I think there's a real likelihood that an earthquake will strike sooner rather than later, and we should just take preventive measures to minimize damage."

Scientists agree with Ms.Johnston.
 
A major New Madrid earthquake is a real possibility; small tremors, some barely felt, are reported every month or so. A major earthquake will more than likely occur in the next 15 to 20 years, according to seismologists.

The New Madrid fault, which stretches from Missouri and Illinois into northeastern Arkansas, poses the highest earthquake risk in the United States outside the West Coast, said Dr. Haydar Al-Shikur, director of the University of Arkansas Earthquake Center, which was started in the early 1990s. "The New Madrid zone is the most active, the most dangerous zone in the
country," Dr. Al-Shikur said.

Dr. Al-Shikur said seismic statistics indicate there is an 80 percent to 90 percent probability of an earthquake of 6.5 magnitude or greater occurring in the next 15 to 20 years.  "Typically, a damaging earthquake in this area - of magnitude 6.0 or greater - occurs about every 80 years," he said. "The last one was in 1895."

An earthquake of magnitude 6.0 could cause severe damage, such as collapsed buildings. A magnitude of 2.5 is the smallest usually felt by humans. Every increase of a whole number means the ground motion is 10 times greater. For instance, an earthquake with a magnitude of 3.0 to 3.9 could cause minimal damage - cracks in old buildings. One of 4.0 to 4.9 magnitude could damage older buildings and cause cracks in most buildings.

Long fault line

The New Madrid fault extends 120 miles south from Charleston, Mo., and Cairo, Ill., through New Madrid, Mo., and down to Marked Tree, Ark., and cuts across the Mississippi River in three places and the Ohio River in two places.

Many seismologists have in the past downplayed the dangers of the New Madrid fault, but new studies indicate that a big tremor in the nation's heartland will occur in the next two decades.

 Karl Mueller, a professor at the University of Colorado at Boulder, recently spearheaded one such study.  "Our evidence shows the New Madrid seismic zone is indeed a threat, which contradicts a recent study of the seismic hazard of the region taken with satellite data," Mr. Mueller said.