A minor earthquake shook Maryland late Monday night. While not severe, it marks the third earthquake to be felt in the state this year.

The 1.8-magnitude earthquake occurred shortly before 11:30 p.m. and was centered in Spencerville, in Montgomery County, according to the United States Geological Survey.

The agency’s website reports that the quake was also felt in Wilmington, Delaware, and Columbia, Maryland.

Earthquakes occur when the earth’s tectonic plates shift.

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With its low rating on the Richter scale, Tuesday’s earthquake falls into the category of a “micro” earthquake. These quakes are not always felt by people but are recorded on local instruments.

Maryland felt a much larger 4.8 magnitude earthquake in April that was centered in New Jersey. People in other Northeastern locations, including New York, Philadelphia and Boston felt that quake.

A 2.3 magnitude earthquake registered in Montgomery County early Jan. 2. That quake originated about 2 miles west of Rockville, according to the U.S. Geological Survey.

This story has been updated to correct the date of the earthquake. It occurred on Monday, June 24.