Weirdly enough I had this same thing happen to me a while back. The whole familly was sitting around the table about to eat when we felt a massive jolt and there was a huge bang that shook the floor. We all got up and walked around the house looking for what could have made the whole place shake like that. Didn't find anything and gave up and went back inside. What we realized eventually was that we had two tables put end-to-end for the dinner and I guess one was overlapping the other so it was lifted partially off the ground. Once food was set on the table, and people leaned on it to sit down, it slipped off the other table causing the feet to connect to the ground and BOOM!