If you've got loud music on and you're bouncing along to it, it's really hard to tell when the vibrations you feel are from you bouncing, and when they're from the earthquake :)

Edit: So was that the 6.9 in Baja California? It seemed a little strong for a 6.9 a few hundred miles away. Maybe they just haven't updated yet?

Edit edit: I am informed that contrary to popular legend, cats make a lousy earthquake warning system. Our cat neither acted strangely beforehand, nor did she seem particularly perturbed when the earthquake was actually happening :)