Scientists' blasts test New Madrid Fault

MEMPHIS, Tenn. -- Seismic tests conducted this week along the New Madrid Fault zone gave scientists a better idea of how loose soil in the area would affect damage during a major earthquake, researchers said.

The earth moved and geysers of water shot hundreds of feet in the air Monday and Tuesday as scientists from the U.S. Geological Survey and the University of Memphis Center for Earthquake Research and Information conducted underground blasts near Marked Tree, Ark., and Mooring, Tenn.

There were no reports of damage and no known complaints from neighbors, officials said.

"Everything went as planned and we got a very good set of data," said Arch Johnston, director of the center.

The testing -- which cost about $70,000 -- found that soil in the area wasn't likely to absorb and blunt an earthquake's damaging seismic waves, Johnson said. Waves from the smaller first blast were measured by instruments 31 miles away.

"It seems that instead of being damped out, it sort of resonated out to longer distances," he said.

The assessment is consistent with recent computer models showing seismic waves would become trapped in the sediment layers, bouncing back and forth between the surface and the hard bedrock thousands of feet below.

Researchers say that could amplify high-frequency ground motions, increasing the hazards from large quakes.

The seismic waves produced by the blasts, which were detonated 160 feet below ground, were measured by seismometers that are part of the $180 million Advanced National Seismic System being installed near several of the nation's quake-prone cities.

A series of strong earthquakes occurred along the New Madrid Fault in 1811 and 1812. One was so powerful it caused the Mississippi River to flow backward and was said to ring church bells on the East Coast.