sound wave
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Local residents felt a slight tremor at about 10 a.m. Saturday. Residents in Newark, Bergen County and Sussex County felt it, too - something that made houses shake and water ripple.

It wasn't an earthquake.

But what was it?

U.S. Geological Survey geophysicist Paul Caruso isn't sure.

"We received a number of reports that people felt something," Caruso said from the National Earthquake Information Center in Colorado. "We don't know what it was."

Local residents took to Facebook and Twitter to describe what they thought was an earthquake.

"I felt it in Margate, thought i was having a stroke!" wrote Patti Fiore.

"I think it was everyone's imagination!" wrote Juanita Rivera.

"Maybe it was God Bowling and he a gotta 7-10 Split?!" wrote Ocean City resident Kevin DeCosta.

Caruso has some theories as to what caused the shaking sensation, but at this point it's merely speculation.

"It could have possibly been a thunderstorm off the coast," Caruso said. "A sonic boom, that's another possibility."

Caruso said this sort of thing happens several times a year, usually off the coast of Florida.

New Jersey has become more earthquake-conscious since August, when a 5.8-magnitude earthquake shook the East Coast.

There would be no repeat Saturday - just some concern and speculation, as New Jersey residents struggled to figure out what made the ground shake.