Thank you for the compliment re my rationality. :)

I did qualify my statement in that I could accept that the amount of motion could very well be due to illusionary effects. I simply doubt that it is 100% illusionary. After all, the ground does indeed move during an earthquake.

Also, that same quake gave me the same experience as your dry wall, except in my case it was the plate glass windows of the school whose parking lot I was in. I never thought glass could bow so much and not break. However, knowing what I do of optics I realize that it does not take much flexing to magnify the reflected image. That apparent magnification goes with the distance from the optic. Since I was about 30-40 yards from those windows, a little bowing would appear quite dramatic.

But back to the ground motion. What we need are hard numbers of how much the ground moves in a quake. This should be quite easy to do. A seismometer is an accelerometer. This is, if I am not mistaken, but the derivative of the actual motion - the rate of change of the rate of motion. Alas, my math skills are likely not up to the task, though. I never took calculus, although I do understand the concept.

I'd think it best to use data from a strong motion station as they are not as prone to saturation as other seismometers.

Anyone here have the skills and time? Or perhaps know where such information already exists?

PS: It seems to me that many of the quake simulations in recent years, although showing exaggerated motion, indicate motions of inches at least, if not a foot or more in strong motions environments. For example, the simulations for the ShakeOut event we recently had here in SoCal.

Brian