Some of the teeth on the 300-million-year-old shark fossil, recently discovered by Jay Wright, a miner for Webster County Coal. The fossil is on display in the lobby of the UK Mining and Mineral Resources Building, 504 Rose St., in Lexington, Ky., Friday, April 8, 2011. Wright recently discovered the fossil 700 feet below the earth's surface at the Dotiki Mine. Researchers at Kentucky Geological Survey and UK's Department of Earth and Environmental Sciences are studying the rare find. Charles Bertram | Staff CHARLES BERTRAM | STAFFBuy Photo

Back when Kentucky was like the Gulf of Mexico, about 300 million years ago, a shark from the Edestus genus swam the seas in what is now Webster County.

It was a big critter — 20 to 25 feet long, weighing about 1,000 pounds — and it had large, sharp teeth, the better to tear apart the soft fish upon which it preyed.

Fast forward to current times: Kentucky has ceased to be a primeval resort for Edestus and its relatives, and hundreds of millions of years of rock cover their skeletons.

But on Feb. 24, Jay Wright, 25, a miner for Webster County Coal, noticed something jutting from the roof of the Dotiki Mine, where he was bolting a roof 700 feet underground.

A piece of rock fell.

Another volley will be fired today in what might be called the Middle America Quake Wars.

In today's issue of Science, a team of researchers report they have looked closely at the New Madrid earthquake fault and found that the potential for a large quake is "a serious threat."

By large quake, they mean strong enough to severely damage places like Memphis, St. Louis and Paducah. Strong enough to break levees along 150 miles of the Mississippi River. Strong enough to rattle Lexington.

That view counters an article in the same publication last spring that found that predictions of a large quake had been overstated.

The earlier research sent tremors through the ranks of scientists who study the New Madrid fault, an ancient scar in the Earth's crust miles beneath the area where Kentucky, Missouri, Tennessee, Arkansas and Illinois meet.

Some scientists, including John Kiefer, an assistant director of the Kentucky Geological Survey, worried that downplaying New Madrid's threat could lead to weakening building codes in the region.

The New Madrid fault is not as well known as some in other parts of the world, but that's because it hasn't caused a major shake in a while. In 1811 and 1812, the fault produced what might have been among the strongest earthquakes ever felt in North America.

There were no seismographs at the time, but the new study estimates that they would have registered a magnitude of 7.5.

There were few people living in this part of the country at that time, but one of the quakes was said to have rung church bells as far away as Boston and Washington, D.C. There were reports of the Mississippi running backward.

The team of scientists who wrote the earlier article was led by geologist Seth Stein of Northwestern University. They used Global Positioning System satellites to measure movement at various places in the region of the fault.

They found so little movement that they concluded that a huge earthquake was not likely to ever happen, and that the giant quakes of the last century might not have been as strong as now thought .

Research for the current article was headed by Karl Mueller, a geologist at Colorado University-Boulder.

They took a very different approach from Stein's team, using backhoes to dig long trenches in the area around Tennessee's Reelfoot Lake.

That allowed them to measure "kink bands" that are formed as the land is pushed upward. Then they used a technique that enhanced relief maps of the area. They also mapped the small quakes that happen frequently.

Their research shows that the fault has stored enough energy since 1811-1812 to produce an earthquake of about a 6.5 magnitude today, although they don't predict when it will happen.

"Our evidence shows the New Madrid seismic zone is indeed a threat," Mueller said. "For the first time we can see how fast the earthquake engine is running and how long it takes to build up energy for a quake."

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Reach Andy Mead at (606) 231-3319, (800) 950-6397 or at amead@herald-leader.com