FAULT FINDER: GEOLOGIST DISCOVERS HOLLY RIDGE

A state geologist has found evidence of a new earthquake fault in the Missouri Bootheel.

Geologist Dave Hoffman of the Missouri Department of Natural Resources discovered possible signs of a past earthquake at an auto salvage yard east of Bloomfield.

He named the fault Holly Ridge because it is within a quarter mile of the forested, Holly Ridge state conservation area.

Faults typically are named by the scientists who discover them. They are named after prominent geographic features, including towns, rivers and land forms, Hoffman said.

While further study is needed, Hoffman believes he has found an earthquake fault.

Hoffman discovered the fault in October while driving along County Road 537.

"I was driving along a road and I saw this cut-bank in a little salvage yard," Hoffman said.

The owner of the property, Jim Burton, had cut into the hillside. "So there was a bank there like a road cut, and I stopped and asked if I could take a look," Hoffman said.

In studying the soil, Hoffman found a layer of silt that had shifted vertically about 20 feet. The shift occurred less than 10,000 years ago, suggesting that one or several massive earthquakes may have struck the region, Hoffman said.

It would take an earthquake of the magnitude of the 1906 San Francisco quake to cause such a vertical shift, he said.

Since discovery of the Holly Ridge Fault, the site has been visited by newspaper and television reporters, and staff from Southeast Missouri State University's earthquake center.

Hoffman and other scientists from the Missouri Division of Geology and Land Survey further examined the site in November.

Burton's house is right next to the fault. "It doesn't bother me," he said Monday.

But Hoffman said the discovery suggests that Bootheel residents have more to worry about than the famed New Madrid Fault when it comes to earthquakes. "There could be a major earthquake in the Dexter area," Hoffman said. "We think that is a real possibility."

But the geologist said there is no way to predict when a major earthquake might occur.

The latest fault is about 30 miles southwest of a set of faults discovered in the Benton Hills area three years ago.

The Holly Ridge Fault may be part of a much larger seismic zone called the Commerce Geophysical Lineament, which extends from near Little Rock, Ark., up through Southeast Missouri and southern Illinois, to Vincennes, Ind.

The huge zone may be about five miles wide, Hoffman said. The zone was identified by scientists with the U.S. Geological Survey based on aerial studies that identified magnetic properties in the ground.

"This zone may represent a zone of weakness in the earth that could be a fault. We think there is an association there, but we haven't been able to actually prove it," Hoffman said.

The zone takes its name from the tiny town of Commerce in Scott County where there is visible evidence of a fault, he said.

Hoffman said the zone originally was known as the Arkansas-Illinois Lineament. The name was changed about two years ago after further research.

As a geologist, Hoffman wonders if other faults might be hidden beneath the ground.

"How many other places are out there like this that we don't know about, scattered throughout the rest of the Midwest?" he asked.

Hoffman said the possibility of a large earthquake zone running through the Bloomfield, Benton Hills and Commerce area poses a greater damage risk for Cape Girardeau than the New Madrid Fault, which is farther south.

Hoffman said some people worry that all this talk of earthquakes will scare away industry. But Hoffman doesn't believe that will happen. It is better to plan for a possible earthquake than ignore it, he said.

Finding new faults isn't easy. "It is partly a matter of getting lucky," he said.

"Whenever we are down in the area and we see a new excavation, we will stop and look," Hoffman said. "That is the only way you are going to find it."