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Local

Professor: Illinois due for a quake

While historic earthquakes hit California, Illinois also sits between 2 seismic zones

DeKALB – Philip Carpenter remembers waking up around 4 a.m. at his home in Sycamore in February 2010 when a 3.8-magnitude earthquake centered in Lily Lake hit the region.

Carpenter, a 62-year-old professor who has studied seismology for 33 years, quickly grasped what was happening.

“First I heard a bang, and then a shaking, and immediately thought it was an earthquake because I’d felt them out West,” Carpenter said in an interview remembering the 2010 quake.

Carpenter, a professor of geology and environmental geosciences at Northern Illinois University, is from California, where he once experienced a 5.9-magnitude temblor.

In the wake of the 6.4- and 7.1-magnitude quakes that struck southern California earlier this month, he says our area could be due for another tremor soon – although probably not on that order.

“Our location is pretty stable,” Carpenter said. “But we haven’t had an earthquake for a while up here, so I think we’re probably due for another small one. We basically have these once about every 10 years. We talk about them being random, but if you look at the distribution of earthquakes over the last 100 years, they tend to cluster.”

Northern Illinois is flanked by seismic zones. The New Madrid Seismic Zone lies to the west, while the Wabash Valley Seismic Zone is to the east. Earthquakes are caused when slabs of rock called tectonic plates shift below the earth’s surface and collide with each other at points known as fault lines.

The resulting impact sends out waves of energy that cause the surface to shake.

That phenomenon leads to earthquakes in this area, too, including a 2.4-magnitude earthquake that occurred in McHenry County in January 2012 and a 2.9-magnitude earthquake that occurred in Lake in the Hills in 2015. He said the 2010 Lily Lake quake was felt throughout the Chicago area, including in Sycamore.

“There was a fault that shifted probably about 6 miles below the surface,” Carpenter. “When you go up to Lily Lake it’s all just soil, so glacial deposits cover all the rocks. When an earthquake occurs, there’s a break in the rock, and it suddenly shifts, and that’s what causes earthquakes.”

Carpenter said he always has a running seismograph near his offices in Davis Hall on the NIU campus, but said the seismograph that sits displayed in Davis Hall was not working at the time of California’s July 5 earthquake.
A backup seismograph was on in the basement of the building.

“There’s a sensor in the basement, the quietest part of the building,” he said. “The seismometer measured ground vibrations, and a cable sends that to a computer, which is the way we display seismographs.”

In the days after the California quakes, the Illinois Emergency Management Agency in a news release urged residents to be proactive in their emergency preparation efforts, in the event Illinois suffered a similar event.

“Creating an environment of education, awareness and preparedness will save lives in Illinois,” said Alicia Tate-Nadeau, acting director of the agency. “While we cannot predict when the next major quake will occur, we can help people learn how to protect themselves and reduce damage to their homes.”

The release included steps homeowners can take to
prevent injuries and property damage, including strapping water heaters and large
appliances to wall studs,
anchoring overhead light fixtures, strapping down televisions, computers and other heavy equipment to prevent tipping, and learning how to shut off gas, water and electrical service in case the lines are damaged.

Carpenter’s research draws a comparison between earthquakes and water table changes, meaning the levels in nearby bodies of water naturally can change over time because of weather cycles, precipitation patterns, geologic changes and even climate change.

“There is a weak correlation between higher rainfall and more earthquakes,” he said. “Typically, we have earthquakes in the spring and winter like in 2010. We don’t see them very often in the late months of the year, or very seldom during the summer, so we’re exploring that idea.”

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