Quake went unnoticed by most in state
But geophysicist asks to hear from folks who felt tremor

The few Minnesotans who actually felt the earth move Wednesday as the shock waves of an Illinois earthquake rolled under the southeast part of the state can count themselves lucky.

Not because they are unscathed, but because they felt it at all.

It is not every Minnesotan who can claim to have experienced a home-state quake.

Of the 12 "historical" earthquakes in Minnesota, only nine were severe enough for anybody to notice. The others occurred when somebody was operating a seismograph machine in the state -- something that's even rarer than earthquakes -- or they wouldn't have noticed at all.

For the record, the quake that struck near Lawrenceville, Ill., at 6:49 p.m. Wednesday registered 5.0 on the Richter . That's enough to cause damage near the center of the quake, but his one did little more in the Lawrenceville area than ring the chimes on a grandfather clock about 11 minutes early and cause a few buildings, and their occupants, to tremble.

In Minnesota, a patient in traction at St. Paul-Ramsey Medical Center saw the apparatus on his bed shaking. The nurses, feeling the hospital sway slightly, concluded that it was an earthquake.

A seismic monitor in the control room for Northern States Power Company's Prairie Island nuclear power plant in Red Wing also picked up the tremor and sounded the alarm. The utility thoroughly checked the power plants Thursday and found nothing amiss. "There doesn't appear to be anything threatening," said NSP spokesman Sam Macalus. "They are analyzing the data at this point."

Val Chandler, a geophysicist with the Minnesota Geological Survey, noted that the seismic monitors at NSP's plants are set to be about four or five times as sensitive as similar monitors in nuclear power plants in earthquake-prone California.

"There hasn't been that much activity around here for over a billion years," Chandler said. Back then, he said, mountains were forming on the Iron Range and, at about the same time, the continent apparently tried to split apart. But other than that, things in Minnesota have been pretty quiet.

And even when we do have our own earthquakes, they are hardly worth waiting for. The most notable one occurred in 1917 near Staples, and that registered only about 4.8 on the Richter Scale. The most recent quake was a 4.6 tremor in Morris in 1975. But Chandler and his colleagues are still very interested in finding out who felt the earthquake and where they were at the time.

He is asking people who felt the quake to send him the details on a post card addressed to Minnesota Geological Survey, 2642 University Av., St. Paul, Minn. 55114.