Spring Break
Scientists say Midwestern seismic zones, quakes not well understood
David Mercer
Issue date: 4/22/08 Section: Campus News
CHAMPAIGN, Ill. (AP) - Scientists say they know far too little about Midwestern seismic zones like the one that rumbled to life under southern Illinois Friday morning, but some of what they do know is unnerving.
The fault zones beneath the Mississippi River Valley have produced some of the largest modern U.S. quakes east of the Rockies, a region covered with old buildings not built to withstand seismic activity.
And, when quakes happen, they're felt far and wide, their vibrations propagated over hundreds of miles of bedrock.
Friday's quake shook things up from Nebraska to Atlanta, rattling nerves but doing little damage and seriously hurting no one. It was a magnitude 5.2 temblor centered just outside West Salem in southeastern Illinois, a largely rural region of small towns that sit over the Wabash fault zone. The area has produced moderately strong quakes as recently as 2002.
But it hasn't been studied to nearly the degree of quake-prone areas west of the Rockies, particularly along the heavily scrutinized Pacific coast.
"We don't have as many opportunities as in California," said Genda Chen, associate professor of engineering at the University of Missouri-Rolla, which sits near the well-known and very active New Madrid fault zone.
"We cannot even borrow on the knowledge they learn on the West Coast" because quakes that happen in California - where tectonic plates beneath the Earth's surface collide - are so different from Midwestern quakes that happen far away from the edges of the nearest plates.
It isn't entirely clear, for instance, whether the Wabash faults are related to the New Madrid faults or not.
Some scientists say they are related, noting that the Wabash faults, which roughly parallel the river of the same name in southern Illinois and Indiana, are a northern extension of the New Madrid zone. Others say they're not.
The New Madrid fault zone produced a series of quakes in 1811 and 1812 that reached an estimated magnitude 7.0, putting them among the strongest known quakes to have occurred east of the Rockies. The quakes changed the course of the Mississippi River and were felt in New England.
The fault zones beneath the Mississippi River Valley have produced some of the largest modern U.S. quakes east of the Rockies, a region covered with old buildings not built to withstand seismic activity.
And, when quakes happen, they're felt far and wide, their vibrations propagated over hundreds of miles of bedrock.
Friday's quake shook things up from Nebraska to Atlanta, rattling nerves but doing little damage and seriously hurting no one. It was a magnitude 5.2 temblor centered just outside West Salem in southeastern Illinois, a largely rural region of small towns that sit over the Wabash fault zone. The area has produced moderately strong quakes as recently as 2002.
But it hasn't been studied to nearly the degree of quake-prone areas west of the Rockies, particularly along the heavily scrutinized Pacific coast.
"We don't have as many opportunities as in California," said Genda Chen, associate professor of engineering at the University of Missouri-Rolla, which sits near the well-known and very active New Madrid fault zone.
"We cannot even borrow on the knowledge they learn on the West Coast" because quakes that happen in California - where tectonic plates beneath the Earth's surface collide - are so different from Midwestern quakes that happen far away from the edges of the nearest plates.
It isn't entirely clear, for instance, whether the Wabash faults are related to the New Madrid faults or not.
Some scientists say they are related, noting that the Wabash faults, which roughly parallel the river of the same name in southern Illinois and Indiana, are a northern extension of the New Madrid zone. Others say they're not.
The New Madrid fault zone produced a series of quakes in 1811 and 1812 that reached an estimated magnitude 7.0, putting them among the strongest known quakes to have occurred east of the Rockies. The quakes changed the course of the Mississippi River and were felt in New England.
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