I was living in West Chester PA in the early 1980's and there was a reported earthquake that I think was centered in Delaware. Didn't so much feel it as heard it. I lived in an apartment complex that had a speed bump right outside my place. I heard a noise sort of like a large, heavy truck going too fast over the bump. I looked but there were no vehicles outside. When I heard the news that evening, it was all abuzz about the earthquake and the timing matched exactly.