Earthquake startles Iowans, who feel tremors from Oklahoma

No, early-rising Iowans, that wasn’t just your imagination. The earth really did shake here this morning.

Shortly after 7 a.m., folks who weren’t snoozing could feel an unsettling rolling sensation for several seconds. Within minutes, the U.S. Geological Survey website posted a notice that a fairly large earthquake had just happened in northern Oklahoma, about 400 miles southwest of Des Moines. The earthquake, near Pawnee, was measured at a magnitude of 5.6, the service reported.

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In Des Moines, the tremor was strong enough to make some floors creak and window blinds sway.

Twitter immediately lit up with startled reports from Iowa down to Texas. “Is it the end of the world?” one Iowan asked. Others joked that it couldn’t really be a temblor here. “That wasn't an earthquake. It was just Slipknot rehearsing in Iowa,” a Twitter wag wrote.

Iowa's not a hotbed of seismic activity. The U.S. Geological Survey website says "Iowa has experienced only minor earthquake activity since the United States obtained control of the state under the Louisiana Purchase in 1803."

As for Saturday's quake, besides Des Moines, people in Iowa City; Kansas City; St. Louis; Chicago; Gilbert, Ariz.; Fayetteville and Little Rock, Ark.; Memphis, Tenn.; and Big Lake in southwest Texas, all reported feeling the earthquake. Dallas TV station WFAA tweeted that the quake shook their studios, too.

Pawnee County Emergency Management Director Mark Randell said no buildings collapsed in the town of 2,200 about 9 miles southeast of the epicenter. “We’ve got buildings cracked,” Randell said. “Most of it’s brick and mortar, old buildings from the early 1900s.”

This isn't Iowa's first earthquake experience. Some other notable shudderings go back to the 19th century.

In July 2004, a 4.5 magnitude earthquake occurred early one morning in northern Illinois, where seismic activity is rare, and could be felt in eastern Iowa. Some Iowans mistook the rumblings for intruders, according to the July 6, 2004, Des Moines Register. The epicenter was about 70 miles southwest of Chicago. No injuries were reported.

The great New Madrid Missouri, earthquakes, of 1811-1812 were the first reported felt in Iowa, says the USGS website. The Geological Survey also includes these incidents:

• The earthquake of Nov. 9, 1968, centered in Illinois, could be felt in Albia, Bloomfield, Burlington, Clinton, Elkader, Muscatine and Walpello. 
• On Oct. 20, 1965, an earthquake in eastern Missouri affected a 160,000-square-mile area, and reportedly caused large cracks in a house foundation in Indianola, Iowa. Effects were also noted at Ottumwa. 
• The Sioux City area was rattled July 3, 1858. Press reports described the tremors as of sufficient force to shake pictures and crockery from their places. On Oct. 9, 1872, Sioux City again experienced a moderately strong earthquake.
• On Nov. 15, 1877, another earthquake was felt throughout Iowa and eastern Nebraska, and in parts of Missouri, Kansas, the Dakotas, Wisconsin and Minnesota. The strongest effects were noted at Columbus, Lincoln, North Platte and Omaha, Neb. However, large cracks in the walls of several buildings in Sioux City resulted from this shock. A second earthquake was reported 45 minutes later.
• Keokuk took the brunt on April 13, 1905. Buildings were shaken, but no serious damage was done. The shock was apparently local in character. Riverton, Iowa, felt ian earthquake on March 1, 1935.
• The 1895 tremor, centered near Charleston, Mo., did some slight damage to a few chimneys in Keokuk. This earthquake was felt noticeably in the southeastern part of Iowa, and probably felt over the whole state.