Northern Illinois University geologist and seismologist Dr. Philip Carpenter continually makes his way through the halls of academia to keep an eye on Northern Illinois’ daily earth movement activity inside the seismology monitoring room in the basement of Davis Hall.
All was quiet on a recent Monday afternoon; there would be no earth tremors today.
“Just a couple trains heading through DeKalb,” Dr. Carpenter said over his shoulder about the seismic results produced by ultra-sensitive ground-tracking machine.
But the results were quite different early Wednesday morning on Feb. 10. At 3:59 a.m., an earthquake measuring 3.8 on the Richter Scale gave Northern Illinois a literal and figurative wake-up call.
The epicenter of the quake was pinpointed near Lilly Lake, Ill., which is located between Geneva and DeKalb, and Carpenter hypothesized that Northern Illinois residents should prepare for more terra firma jolts, and researchers must do more to study the earth under Illinois.
According to the NIU scientist, Illinois earthquake epicenters near the Mendota-Amboy area are nothing new, but what was termed “the Sycamore quake” in February has left Dr. Carpenter puzzled and searching for answers.
“About every 10 years we have an earthquake like this,” Dr. Carpenter said. “These kinds of earthquakes are sporadic – there’s no foreshocks, there’s no aftershocks – that we know of. In 2004, there was one of these down by Prairie Center, and that was the same size (as last week’s quake).
“There was one down by Amboy in 1999, and there was one in 1972 in the Amboy area,” he continued. “What we believe causes the Amboy quakes is a warp in the rocks in the Illinois Basin. That warp has a fault in it.”
Dr. Carpenter’s theory is that plated rock miles below the Illinois surface is under immense pressure and “pops” around the region. These “pops” are the 3.8 quakes Illinois witnesses every decade or so.
And according to the geological clock, the Amboy area is overdue for another earth adjustment.
“There’s a pretty good chance of having another one down there,” Dr. Carpenter said of the earthquake possibilities near Amboy. “Because we’ve had two down there in the past 30 years. That area is more active, so we can expect something in the next 10 years.”
Though the threat is lurking and unpredictable, the strength of an Illinois-epicenter quake is not an alarm for concern. Prairie State tremors measure between 3.0 and 4.0 on the Richter Scale – rather small earthquakes compared to the recent Haitian quake or the devastating earthquakes that have rocked California.
“One of the characteristics of earthquakes in this area is that they are felt over enormous distances; the waves don’t get absorbed very quickly,” said Dr. Carpenter. “If they had a 7.0 (on the New Madrid Fault) we’d feel it in Northern Illinois. We’ve had earthquakes centered near Lawrenceville (in the 1980s) that have been felt in the Quad Cities and into Wisconsin.”
Carpenter would like to start research in the Sycamore/Lilly Lake area with portable seismographs and other equipment that would help to unearth whether new fault lines have been born underneath Illinois’ crust.
“I think so; that’s my opinion,” Dr. Carpenter said about new faults. “There’s never been an earthquake in Sycamore and in the DeKalb area. It’s pretty much a mystery that I’d like to explore.”
Carpenter also warns Illinois citizens that the biggest threat from earthquakes comes from not the New Madrid Fault in Missouri but the Wabash Valley Fault Line located northwest of Evansville, Ind. Geological research of this area has produced evidence of “massive” prehistoric earthquakes.