a number of years ago, i worked in one of the downtown LA office towers when a 5.x earthquake hit. it was a jolt and rumble, and looking out the window, we saw the other towers nearby swaying back and forth. then we realized we were also swaying back and forth. it was unnerving to say the least. the little engineer in me eventually kicked in to point out that that engineered-in flexibility was what kept us from breaking apart and crashing into the ground.