A rare earthquake rippled in and around Alexandria in western Minnesota early Friday, prompting numerous middle-of-the-night calls to emergency dispatchers and acting as a seismic alarm clock for one royal wedding fan.

The temblor at 2:20 a.m. measured 2.5 in magnitude, falling into the "weak" category, according to the U.S. Geological Survey. There were no reports of damage or injury.

The quake probably "felt like a truck rumbling by or thunder," said USGS geophysicist John Bellini.

Bellini said the agency collected several dozen "felt reports" on its website from citizens in Alexandria and nearby communities such as Brandon, Carlos and Garfield.

While there is a margin of error in pinpointing any epicenter, the USGS put this one on the southwestern edge of Alexandria, near the town's airport.

"I felt it, oh, yeah," said Sandy Pederson, who lives on the north side of Alexandria and is an office staffer at KXRA Radio (1490 AM) in town.

"I happened to be in bed awake," Pederson said. "My first thought was that it was thunder. ... It shook the house."

When Pederson reported for work later in the morning at the radio station, callers to the studio were numerous and were reporting their experience from "quite a large area" around Alexandria, she said.

Jefferson High School science teacher Tom Smith said he heard from about eight or nine people who felt the tremor, some of them describing it as like a sonic boom. Several said their walls and windows had rattled, he said.

Caroline Petefish, a middle-school teacher who lives about 10 miles north of Alexandria, said, "I felt it and thought, 'This is what an earthquake feels like.' The whole house shook and dishes, etc., rattled."

She said she "couldn't get back to sleep, so I was up in plenty of time for the royal wedding."

Douglas County Sheriff's Sgt. Tom Egan said emergency dispatchers took 25 to 30 calls. Some reported noise and minor movement, including the slight bounce of ceiling tiles.

Earthquakes centered in Minnesota are "very uncommon," Bellini said. Most since the state joined the union have come in the western part of Minnesota.

According to a list of earthquakes maintained by the University of Minnesota, Morris, the last earthquake in the state was in 1994 in Yellow Medicine County and measured 3.1.

The most recent quake in the Twin Cities area was April 24, 1981, according to the Morris list. It measured 3.6 and was centered in Cottage Grove.

The largest "instrumentally located" quake in Minnesota, the USGS says, struck on July 9, 1975. That 4.6-magnitude temblor caused minor damage to walls and foundations of basements in Stevens County around Morris. It was also felt in Iowa, North Dakota and South Dakota.

Paul Walsh • 612-673-4482