Midwest Quake Shocks Residents, but not Scientists

By Anastacia Mott Austin

We all know the hazards of where we live. The south has hurricanes, the Midwest tornadoes, and California has earthquakes…right?

Wrong. Those who take comfort in thinking they know what to expect of their local geography may want to rethink those comfort zones.

A 5.2 magnitude earthquake hit southern Illinois at about 4:37 Friday morning, shocking residents out of bed and leaving them scratching their heads to figure out what was going on. The quake was felt as far away as parts of Florida and Georgia, and was the largest quake the area has felt in 40 years.

"I woke up when my windows started rattling," said Stephanie Kellerman, a Kentucky resident, to reporters. "A few seconds later some plaster fell from my ceiling, and my cats reacted by fleeing the bedroom and scattering down to the first floor."

The topographical makeup in the Midwest means that quakes are felt in a far larger area than those typically on the West Coast. The soil structure is more solid, not interrupted by frequent fractures like the soil in the Western United States, so seismic waves travel longer distances.

"It's well-known the same size earthquake can do a lot more damage in the eastern U.S., where there's not [as much] geologic activity," said Nano Seeber, a researcher at the Lamont-Doherty Earth Observatory at Columbia University. "In the eastern U.S., the rocks are stronger. The waves go through and go for a longer distance," said Seeber to reporters.

In addition, seismic retrofits, or specific building modifications that allow buildings to withstand earthquakes, are common in the West but very rare in other areas. This means that damage from a medium-to-large quake would be far worse in areas of the country with no retrofitting.

Area seismologists, however, were not surprised by the quake and say that earthquakes in Illinois are not that uncommon.

In fact, while states like California get all the press for their earthquakes, which are admittedly much more common, there are more than 26 earthquake risk areas, say experts, including areas of New York, Massachusetts, Tennessee, and Indiana.

"Southern Illinois has had earthquakes of this size throughout history," said Seeber, "Is this an earthquake zone? Yes."

The quake appears to have occurred along the Wabash Valley fault line, not the more unstable New Madrid fault line, which is further south.

The last earthquake near this magnitude occurred in 2002, when a 5.0 quake rocked the area. Before that, 1968 was the last time a quake of this particular magnitude was felt.