I was at work when it happened but the wife called and said the whole house shook and rattled - they were concerned around here that it was the nuclear station at Hope Creek (3 mi south) or the Dupont-Chambersworks chemical plants in Carney's Point (5 mi north). The epicenter was about 7 mi N/E of here in Elsinboro. As Tony noted, they're rare enough around here to not be high on the list of "what the heck was that?" conjecture...
On the other hand, had the quake leveled the town of Salem, it would have done over $100 worth of damage..
