No damage was reported in Indiana or Illinois after an earthquake with a preliminary magnitude of 5.2 rumbled through the Midwest Friday morning.
A powerful aftershock shook the area at 10:20 a.m. and registered a 4.6 magnitude.
The quake, recorded at 4:37 a.m., shook skyscrapers in Chicago's Loop, 230 miles north of the epicenter, and in downtown Indianapolis, about 160 miles northeast of the epicenter. Residents in Milwaukee, Cincinnati, Louisville and St. Louis also reported feeling the earth shake.
The U.S. Geological Survey Web site said the quake was centered near West Salem, Illinois, or about 40 miles northwest of Evansville, Indiana.
Initially pegged as a 5.4 earthquake, the U.S. Geological Survey revised its estimate to give it a value of 5.2.
The U.S. Geological Survey said dozens of aftershocks were rumbling through the already-shaken Midwest later in the morning.
USGS Geologist Gary Patterson said the most powerful aftershock happened around 10:20 Friday and had a 4.6-magnitude.
Two other aftershocks measured 2.6 and 2.5.
Reports of people who felt the quake quickly spread throughout the Region early Friday.
Highland, Crown Point, Dyer, Valparaiso, Winfield, Demotte, Cedar Lake, Lowell, Hobart, Munster, St. John, Schererville, Portage and LaPorte all had residents reporting they felt their homes shake and wondered what happened.
Indiana State Police Cpl. Jeff Council of the LaPorte District said his family felt the quake. Council, a resident of LaPorte County, said he was in the shower at the time of the quake and noticed his towel had moved from on top of the toilet to across the room.
"I asked my wife if she moved it and she said, 'No,'" Council said. "She felt it and came running into the bathroom because she thought I fell."
Council said the LaPorte District of the Indiana State Police received "a few calls" from area residents asking what had happened after they felt the quake.
Crown Point, Hobart and Lake County police dispatchers said they felt their chairs shaking and received a few calls from residents asking what had happened. Hammond police reported receiving "a lot of calls" from concerned residents, while their counterparts in Dyer, Highland, Munster, St. John, Schererville and Lowell said they received just a handful of inquiries.
Porter County police spokesman Lt. Chris Eckert said he wasn't aware of any spike in calls to the county dispatch center as a result of the earthquake, and he had no reports of any damage caused by it.
"I was up about 4 a.m., but I didn't feel any shaking or anything," Eckert said.
Many police departments said residents called asking if a transformer blew or if there had been some sort of explosion or accident.
Janet Henrichs of Cedar Lake said the quake shook her bed.
"My husband was on the couch and I was in bed and the bed started shaking and my drop-leaf table was hitting the wall," Henrichs said. "...My husband said the TV was creaking."
In Dyer, Lorraine Swieringa was up early on her computer when things started to shake.
"The windows were rattling and then the walls," Swieringa said. "I thought maybe they were doing some blasting at the Thornton quarry."
Swieringa said her son just moved back to the Region from California.
"I was happy because I thought I wouldn't have to worry about him being in earthquakes anymore," she said with a laugh.
Margueritte Lork Kalbrunner of Hammond said she broke her arm when she was 10 years old and when it starts to ache, she knows bad weather is coming. Kalbrunner said her arm started hurting around 3:30 a.m.
"I was sleeping on the couch and around 4:30, it felt like someone was trying to lift the couch," the Hammond senior said.
Kalbrunner said she studied music in France as a young woman and traveled all around the world, and never experienced an earthquake.
"I was in the Alps, in Bavaria, you name it and I've never experienced anything like this," she said.
Eileen Kubisz of Highland said she was awake just after 4:30 a.m. when she heard a sound she hadn't heard in years.
"It sounded like wooden wheels going down a cobblestone street," Kubisz said. "I got up to look outside to see what it was and it was over like that, just as soon as it started."
Kubisz, a 43-year resident of Highland, said she remembers a small earthquake being felt in the Region almost 20 years ago, but she didn't feel that one.
"I was on a bicycle crossing the boulevard at the time and they say if you're in motion, you don't feel it," she said.
The strongest earthquake recorded in Illinois was in 1968, a 5.3-magnitude temblor centered near Dale in Hamilton County, about 75 miles southeast of St. Louis, according the USGS. Minor damage was widespread, but there were no serious injuries or fatalities.
The Midwest, most notably southeast Missouri and southwest Illinois, is home to the New Madrid fault, a network of deep cracks in the earth's surface.
The fault, at the center of the country's most active seismic zone east of the Rockies, produces numerous small quakes a year, most too weak to be noticed by the public.
But in 1811 and 1812, it produced a series of earthquakes estimated at magnitude 7.0 or greater. It was not immediately clear Friday if the fault extends as far east as West Salem.
Even before Friday, earthquakes -- or the possibility of them -- in the central U.S. were getting plenty of attention.
Early next month, agriculture extension officials from various regional states already are scheduled to convene an earthquake summit, hosted by the University of Illinois' extension service.
Planners of the New Madrid Earthquake Emergency Preparedness Conference in the Ohio River community of Metropolis, Ill. say representatives from Illinois, Arkansas, Indiana, Missouri and Tennessee are to attend.
-- Times Staff Writer Ken Kosky and The Associated Press contributed to this report.