From Boston.com:
"At approximately 1:51 PM this afternoon a small shockwave from the 5.9 magnitude earthquake that hit Virginia rumbled through the Boston area. The temblor was minor, however, it was large enough to cause PTN's man-****s to begin vibrating at the exact correct frequency, causing them to begin to smack together, effectively magnifying the initial shockwave and causing several seconds of shaking throughout Massachusetts"
That's all true. It is on the interwebs