[math-fun] Earthquake magnitudes

I saw a press conference on the internet where the Chinese govt officials were saying that the 2008 Olympics were safe, because the facilities were constructed to survive an 8.0 earthquake. I also understand that the recent Sichuan quake was magnitude 7.9. If I understand the Richter scale, it is log_10(amplitude), so amplitude 8.0 should be 26% greater than amplitude 7.9. http://en.wikipedia.org/wiki/Richter_scale Is 26% much of a safety margin?