I've heard of people seeing large waves in concrete during quakes, with no cracks later in the concrete. Its supposed to be a vibration in the eye or some such thing. Otherwise, I don't know whether or not seismic waves can be seen: I'd guess it was possible if the amplitude was high enough and observing conditions good. I'm not sure what the amplitudes would be for the worst case San Andreas quake in LA basin...but I'd guess a couple of cm, maybe more.
Chris