Earthquake tremors rattle Chicago

At 4:36 A.M. Friday morning, tremors swept across the Chicago area, lasting for about 15 seconds and shaking high rises. According to a dispatcher on the city information line, hundreds of people began calling in from across the city immediately to ask if it had been an earthquake.

In Old Town, emergency sirens began sounding just twelve minutes later as car horns honked from the streets. More on this developing story as it comes in.

UPDATE 4:59 A.M.: A reader, Ed, has posted a link to the seismograph.

UPDATE 5:16 A.M.: The Associated Press reports the quake, given a preliminary magnitude of 5.4 (later downgraded to 5.2), centered 6 miles from West Salem, Ill., 66 miles northwest of Evansville, Ind.

There were no immediate reports of injuries.

UPDATE 5:39 A.M.: The U.S. Geological Survey measured the quake at 7.2 miles below the surface and occurred in the Illinois basin-Ozark dome region that covers parts of Indiana, Kentucky, Illinois, Missouri, and Arkansas and stretches from Indianapolis and St. Louis to Memphis.

Moderately frequent earthquakes occur at irregular intervals throughout the Illinois basin, according to the U.S.G.S. National Earthquake Information Center. The largest historical earthquake in the region, 5.4 on the Richter Scale, damaged southern Illinois in 1968. Moderately damaging earthquakes strike the region each decade or two, and smaller earthquakes are felt one to two times a year.

UPDATE: 6:05 A.M.: A tour of the Loop turned up no emergency vehicles or obvious damage at major construction sites. Reports from city agencies say there have been no reports yet. If you see aftereffects in your neighborhood or on your block, let us know.

UPDATE 7:04 A.M.: WBBM still says there have been no damage reports. The U.S.G.S. has downgraded the magnitude of the quake to 5.2 on the Richter Scale. The Chicago Tribune’s iPhone blogger has a running post going, featured on their home page. Some great comments below it…

UPDATE 7:19 A.M.: Lucas Griswold, a dispatcher in West Salem, Ill., told the AP that the Edwards County sheriff’s department has received reports of minor damage, but no injuries. At just six miles away, West Salem was one of the closest towns to the epicenter.

UPDATE 7:54 A.M.: The Chicago Tribune reports that a metal rod sticking out of the pavement near the Edens Expressway near Dempster disabled at least seven cars this morning. Illinois State Police say the rod may have been exposed as a result of the tremors.

UPDATE 7:59 A.M.: Reports are rolling in:

• “I was trying to figure out if I needed to take my medicine” - CLTV takes a call from a rattled Southside (video)
• Bricks tumbled from a 4-story building in Louisville, so far the only tangible damage reported.

UPDATE 8:07 A.M.: Illinois’ six nuclear power plants report no damage, though they claim to have partially staffed their emergency response teams, according to WBBM.

UPDATE 9:22 A.M.: Chicago’s CBS 2 station has about three pages full of comments from readers. They asked viewers to share stories of where they were and what they felt when the earthquake hit.

Janet Clem, 37, looks at the damage to her home in Mt. Carmel, Ill., Friday morning April 18, 2008 after the 5.2 early morning earth quake. (AP Photo/Daniel R. Patmore) 

UPDATE 10:06 A.M.: In Mount Carmel, 15 southeast of the epicenter, a woman was trapped in her home by a collapsed porch but was quickly freed and wasn’t hurt, Mickie Smith, a dispatcher at the police department, told the AP.

Also in Mount Carmel, a two-story apartment building was evacuated because of loose and falling bricks. Police cordoned off the building, a 1904 school converted to residences. 

The department took numerous other calls, though none reported anything more serious than objects knocked off walls and out of shelves, Smith said.

UPDATE 10:56 A.M.: An aftershock was reported at 10:14 a.m. preliminarily registering at 4.6 on the Richter Scale, acccording to the U.S. Geological Survey.

There has been as many as six aftershocks, USGS geophysicist Angel Gutierrez told the Chicago Tribune. The rumbling could be felt at least as far away as Chicago.

“We’ve had a few before this one, but this one is the biggest,” said Gutierrez, who said two of the earlier shocks registered at 2.2 and 2.5.