Just a little shake.
Check it out:

Trembling earth and a mysterious loud noise startled some residents in Maryland on Thursday, though officials said it wasn’t an earthquake and one expert said it may have been a sonic boom.

Jessica Waters, the communications manager in Ocean City, said her office received dozens of calls from residents starting about noon. Residents also took to social media reporting what they heard and felt.

“We didn’t feel anything at city hall,” Waters said, but calls came in from all over the resort town and as far west as Berlin, 11 miles away. There were no reports of damage or injuries.