[Video Link] Here's a video (well, real audio with some graphics) of the Los Angeles Philharmonic performing Ravel's "Daphnis and Chloé during a 5.1 magnitude earthquake. It's pretty interesting to hear the gasps and murmurs of the audience followed by the lovely music continuing without a hitch.
A couple of things to note here:
-Walt Disney Concert Hall was built only 10 years ago and is made to withstand seismic activity.
-I work for the LA Phil and had a hand in making this video.