InfrastructureEarthquake in Illinois could portend an emerging threat
Earthquakes in the Midwest section of the United States were mostly the result of the New Madrid Fault in Missouri’s bootheel; seismologists now worry that the 18 April, 5.2 Richter earthquake which shook the Midwest originated in the Wabash Valley Fault — meaning that another fault is becoming active
To the surprise of many, the earthquake on 18 April 2008, about 120 miles east of St. Louis, originated in the Wabash Valley Fault and not the better-known and more-dreaded New Madrid Fault in Missouri’s bootheel. The concern of Douglas Wiens and Michael Wysession, seismologists at Washington University in St. Louis, is that the New Madrid Fault may have seen its day and the Wabash Fault is the new kid on the block. The earthquake registered 5.2 on the Richter scale and hit at 4:40 a.m. with a strong aftershock occurring at approximately 10:15 a.m. that morning, followed by lesser ones in subsequent days. The initial earthquake was felt in parts of sixteen states. “I think everyone’s interested in the Wabash Valley Fault because a lot of the attention has been on the New Madrid Fault, but the Wabash Valley Fault could be the more dangerous one, at least for St. Louis and Illinois,” said Wiens, professor of earth and planetary sciences in Arts & Sciences. “The strongest earthquakes in the last few years have come from the Wabash Valley Fault, which needs more investigation.” Wiens said that seismologist Robert Hermann of Saint Louis University, Gary Pavils of Indiana University, and several geologists including Steven Obermeir of the U.S. Geological Survey (USGS), have made studies of the Wabash Valley Fault. Pavils also has run a dense local array of stations and recorded many very small earthquakes at the Wabash Valley Fault. Hermann has studied the 1968 magnitude 5.5 earthquake, the largest ever recorded there. Obermeir and others have found disturbed sediments from previous earthquakes along the fault with estimated magnitudes of about 7 on the Richter scale over the past several thousand years.
According to Wysession, there are 200,000 earthquakes recorded every year, with a magnitude 6 earthquake happening every three days somewhere in the world. “There hasn’t been a magnitude 6 earthquake on the New Madrid zone in more than 100 years, yet in 20 years there have been three magnitude 5 or better earthquakes on the Wabash Valley Fault,” said Wyssession, associate professor of earth and planetary sciences. “There is evidence that sometime in the past the Wabash Valley Fault has produced as strong as magnitude 7 earthquakes. On the other hand, the New Madrid Fault has been very quiet for a long time now. Clearly, the Wabash Valley Fault has gotten our deserved attention.” Wysession
