When a 4.2 earthquake struck Michigan on Saturday, May 2, the common reaction was: Earthquake? In Michigan? Seriously?

The surprise was not misplaced. Earthquakes in Michigan are rare and tend to be minor.

In fact, Saturday's quake was the state's most powerful earthquake since 1947.

The quake occurred about 12:20 p.m., with an epicenter about five miles south of Galesburg in Kalamazoo County.

RELATED: Complete coverage of the Michigan earthquake

Below are seven facts about earthquakes in Michigan, drawn from the U.S. Geological Survey and other government websites.

1. Michigan has "very small probability of experiencing damaging earthquake effects," the Federal Emergency Management Agency says.

In fact, most tremors felt in Michigan originate elsewhere.

Michigan normally does not have earthquakes, the state's emergency preparedness web page says. "However, we can suffer effects from earthquakes in neighboring states that have a higher likelihood of them."

2. One of the earliest records of earthquake tremors felt in Michigan occurred in 1811 and 1812 from the New Madrid earthquakes in southeast Missouri.

Four earthquakes, each estimated at a magnitude of between 7.0 and 8.1, occurred between Dec. 11, 1811, and Feb. 8, 1812, in southeast Missouri and northwest Arkansas.

"As many as nine tremors from the New Madrid earthquake series were reported felt distinctly at Detroit," the U.S. Geological Survey website says.

If a similar earthquake occurred today in the New Madrid Seismic Zone, it could result in "the highest economic losses due to a natural disaster in the United States," according to a 2008 FEMA report. Michigan was not among the states listed at high risk in the report.

Those were the first well-recorded tremors. However, Wisconsin historian Dave Thorson said a 1793 journal references tremors near the Porcupine Mountains on Lake Superior. The journal was written by Jean Baptiste Perrault, a prominent fur trader in the late 18th and early 19th century.

In addition, a 1977 state document says quake tremors in Michigan "were documented as early as 1638 by French Jesuit missionaries."

3. Between 1872 and 1883, Michigan had a number of moderate earthquakes.

On Feb. 6, 1872, three shocks lasting 30 seconds were reported at what is now Bay City. Tremors strong enough to frighten horses were felt around Dearborn on Aug. 17, 1877.

On Feb, 4, 1883, an earthquake cracked windows and shook buildings at Kalamazoo. The shock was felt in southern Michigan and northern Indiana, and even as far away as St. Louis.

4. "A series of unusual occurrences in the Keweenaw Peninsula mining area form a significant part of the seismic history of Michigan," according to the USGS.

"The first disturbance was on July 26, 1905 at about 6:20 in the evening," the USGS website said. "At Calumet there occurred what appeared to be a terrific explosion.

"Chimneys fell with a crash and plate glass windows were broken. The explosion was heard far down in a mine and the shock was felt all over the Keweenaw Peninsula area and as far away as Marquette, about 70 miles southeast across Lake Superior.

"Ten months later, on May 26, 1906, a similar phenomenon occurred. Train rails were twisted, and there was a notable sinking of the earth above the Atlantic mine. The disturbance was reported felt over an area about 30 to 40 miles in diameter.

"Another shock occurred in the same region on January 22, 1909. A rumbling tremor was felt around Houghton and was believed to be caused by the crushing of pillars in a mine," USGS website said.

Today, the Keweenaw earthquakes "are generally dismissed as mine collapses," according to historian Lisa Shiel.

5. Michigan's strongest earthquake on record occurred on Aug. 9, 1947, about 35 miles from the epicenter of Saturday's quake.

The 1947 had a magnitude of 4.6 and was centered near Coldwater. It damaged chimneys and cracked plaster over a large area of south-central Michigan and was felt as far away as Muskegon and Saginaw and parts of Illinois, Indiana, and Wisconsin.

6. The most recent Michigan earthquake of at least 3.0 occurred on Sept. 2, 1994.

The epicenter of the 1994 quake was Potterville, which is southwest of Lansing, and it had a magnitude of 3.5. It was felt as far away as Grand Rapids and Jackson.

7. Earthquakes in this part of the country are typically felt over a much broader region than West Coast quakes.

"East of the Rockies, an earthquake can be felt over an area as much as ten times larger than a similar magnitude earthquake on the west coast," the USGS website says.

A magnitude 4.0 eastern U.S. earthquake typically can be felt as far as 60 miles from where it occurred, and it infrequently causes damage near its source. A magnitude 5.5 eastern U.S. earthquake usually can be felt as far as 300 miles from where it occurred, and sometimes causes damage as far away as 25 miles.

Saturday's earthquake could be felt in parts of Ohio, Indiana, Illinois and Wisconsin, as well as southern Ontario.

Julie Mack is a reporter for Kalamazoo Gazette. Email her at jmack1@mlive.com, call her at 269-350-0277 or follow her on Twitter @kzjuliemack