Perhaps you felt it, perhaps you didn’t. The seismic waves from the November 25th, 1988, earthquake passed beneath the feet of everyone reading this article, but your reaction would have depended on a number of factors, chief amongst them being your distance from Chicoutimi or Jonquiere, Quebec. That being equal, your reaction would have depended on the nature of the ground beneath you, and your "coupling" to that ground– That is, it would have varied if you were walking, riding in a car, living in a single or multistory building, in bed, in the bath, and so on.