Small quakes along New Madrid fault not uncommon

Published 12:22 am Wednesday, December 23, 2009

The New Madrid fault line has been rumbling again. And while an earthquake expert says the recent series of small quakes isn’t unusual, it is a reminder of what the active fault is capable of.

Four small quakes have been centered near New Madrid in southeast Missouri in the past week, according to the U.S. Geological Survey. The largest was a magnitude 3.1 quake on Friday that was felt in parts of Missouri, Arkansas, Tennessee and Kentucky. No damage was reported. The others were a magnitude 1.7 on Dec. 15, a magnitude 1.3 on Dec. 16 and a magnitude 1.4 on Friday.

Robert Hermann of the Earthquake Center at Saint Louis University said a quake large enough to be felt happens about once a month in the region, and quakes with magnitude 2.0 and smaller happen on an almost daily basis.

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In fact, according to a map on the Web site for the Center for Earthquake Research and Information in Memphis, Tenn., 15 earthquakes have occurred along or near the fault this month alone, including four on Friday. Only three were above a magnitude 2.0.

“That’s really about the most active place in the eastern United States,” Hermann said. “It’s a strange little hot spot.”

The fault line is best known for some of the most violent earthquakes to ever hit the U.S., a series of four in 1811 and 1812. The quakes were estimated at magnitude 7.5 to 8.0, so strong the Mississippi River reportedly flowed backward. Damage occurred as far away as Washington, D.C., and Charleston, S.C.

Tales from survivors were shocking. Some New Madrid residents saw large cracks open in the ground. The crew of a steamboat mooring overnight at a Mississippi River island reportedly awoke to find the island had disappeared below the water.

Experts have long debated whether the fault line is capable of producing another major earthquake. Hermann isn’t willing to bet that it won’t, saying there’s too much at stake to become complacent.

“Some argue that 1811 and 1812 were one-shot affairs, but it’s prudent not to ignore that possibility, and it’s prudent to take whatever steps are possible to prepare,” he said.

Much of the region has done just that. From St. Louis to Memphis (both are roughly 150 miles from the fault line) and at small towns in between, highways and bridges have been retrofitted to stand up to an earthquake. Major new buildings are reinforced to make them more capable of withstanding the next big quake.

Regardless of whether another big earthquake occurs along the New Madrid fault line, the preparedness will pay off, Hermann said.

“It’s a good thing, no matter what type of natural disaster affects the region in the future,” he said.

On the Net:

Saint Louis University Earthquake Center:

Center for Earthquake Research and Information in Memphis:

U.S. Geological Survey — Earthquakes Hazard Program: