E-Defense, World's Largest Earthquake Seismic Testing Table
alatown.com
alatown.com
It's done for high value structures that have to be functioning through emergencies, like emergency management centers and hospitals.
[edit I can't find documentation for this: I believe that the Bay Bridge has some of the biggest ones ever made, at roughly 9 feet of travel. (Though that was 20 years ago, and may not be current)]