I read a story a few years back about an earthquake in the Yellowstone area, but I cannot find it. Searching the internet, I believe it was the 1959 7.3 Hebgen Lake, Montana earthquake... sometimes called the 1959 Yellowstone earthquake.
One guy thought he had a bear under his cabin making a racket. From way down a road, a guy watched as the ground rolled with waves, pitching cars into the air as a wave passed under them. I recall reading that one guy ran wildly out of a privvy with his pants around his knees and proceeded to run right into a tree.
It would have been a good story to post, but I cannot find it. It was a first-hand account and it was well written.