1.8 magnitude earthquake felt throughout Maryland

BALTIMORE -- A 1.8 magnitude earthquake shook Maryland on Tuesday morning, just before 11:30 a.m.  While not severe, it marks the third earthquake to be felt in Maryland this year. 

The earthquake was centered in Montgomery County, Maryland, in Spencerville, according to the United States Geological Survey.

According to the USGS website, the quake was also felt in Wilmington, Delaware and Columbia, Maryland. 

Earthquakes occur when the earth's tectonic plates shift.  

With it's 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.