Scientists say Midwestern seismic zones, quakes not well understood
David Mercer
Issue date: 4/22/08 Section: Campus News
That distance of well over a thousand miles sounds impressive, but experts say quakes that happen in the Midwest commonly radiate out for hundreds of miles because of the bedrock beneath much of the eastern United States.
"Our bedrock here is old, really rigid and sends those waves a long way," said Bob Bauer, a geologist with the Illinois State Geological Survey who works in Champaign.
He compared the underground rock, which in much of the Midwest lies anywhere from a few thousand feet to just a few feet below the earth's surface, to a bell that very efficiently transmits seismic waves like sound.
"California is young bedrock," he explained. "It's broken up ... like a cracked bell. You ring that, the waves don't go as far."
The question of whether Friday's quake was centered along a branch of the New Madrid zone or not is of more than academic interest. The area even now produces smaller, very regular quakes, and experts say it still has the potential to produce a quake that could devastate the region.
The Wabash faults have the potential to do the same, at least based on distant history, said Columbia University seismologist Won-Young Kim.
The strongest quake produced in recent history by the Wabash was a magnitude 5.3 in southern Illinois in 1968, but researchers have found evidence that 4,000 to 6,000 years ago, much stronger quakes shook the region, Kim said, as strong as magnitude 7.0 or more.
A similar quake is still possible, if the region is given time to build up enough energy, Kim said. But knowledge about the area is too thin to say whether that's likely, he added.
Copyright 2008 The Associated Press.
"Our bedrock here is old, really rigid and sends those waves a long way," said Bob Bauer, a geologist with the Illinois State Geological Survey who works in Champaign.
He compared the underground rock, which in much of the Midwest lies anywhere from a few thousand feet to just a few feet below the earth's surface, to a bell that very efficiently transmits seismic waves like sound.
"California is young bedrock," he explained. "It's broken up ... like a cracked bell. You ring that, the waves don't go as far."
The question of whether Friday's quake was centered along a branch of the New Madrid zone or not is of more than academic interest. The area even now produces smaller, very regular quakes, and experts say it still has the potential to produce a quake that could devastate the region.
The Wabash faults have the potential to do the same, at least based on distant history, said Columbia University seismologist Won-Young Kim.
The strongest quake produced in recent history by the Wabash was a magnitude 5.3 in southern Illinois in 1968, but researchers have found evidence that 4,000 to 6,000 years ago, much stronger quakes shook the region, Kim said, as strong as magnitude 7.0 or more.
A similar quake is still possible, if the region is given time to build up enough energy, Kim said. But knowledge about the area is too thin to say whether that's likely, he added.
Copyright 2008 The Associated Press.
Be the first to comment on this story