A small earthquake rocked parts of Somerset County early Friday morning.

The U.S. Geological Survey says the magnitude-2.7 quake hit at 3:41 a.m., and was centered roughly 2 miles north of Bernardsville at a depth of 3½ miles. It was initially reported as a 2.5-magnitude quake.

The quake occurred along the Ramapo Fault, which runs from Harrisburg, Pennsylvania, to near Poughkeepsie, New York.

Mendham resident Jeremiah O'Connell says he heard a big blast this morning. "In fact, I went upstairs and thought maybe my grandson fell out of bed," he says.

Dr. Won-Young Kim of Columbia's Lamont-Doherty Earth Observatory says an earthquake this size is fairly common. "When earthquakes are shallow, the shaking is a little bit more intense than the deeper ones," says Dr. Kim.

The USGS says smaller earthquakes are felt in the region every two to three years.

Dr. Kim says an earthquake similar to this size shouldn't cause any damage. However, because northern New Jersey is so populated, he says a magnitude-4.0 earthquake could cause some damage.

"We don't expect it, but we can't rule out that it may not happen because it has happened before. It's different from California where we know the fault...so we can predict roughly what size to be expected," says Dr. Kim

The last earthquake reported in New Jersey had a magnitude of 1.9 and happened about 17 miles east-southeast of Trenton on Dec. 13, 2014.

The Associated Press wire services contributed to this report.