The following e-mail you may find of interest.  It indicates 
a maximum ground acceleration of about 1 g (of gravitational 
acceleration).  Beyond 25 km ground motion amplitude is 
inversely proportional to distance.  Above .4 g many 
California engineers prefer shear resistant buildings, but 
distrust solid shear walls. 

From 
http://vulcan.wt.usgs.gov/Glossary/Seismicity/description_ma
gnitude.html
Description of earthquake magnitudes and intensity we find a 
magnitude 5 earthquake at about 10 kilometers from the 
epicenter to be 1.1 millimeters.  If we use the increase by 
10x for each one magnitude change, then for magnitude 9 we 
would get 11 meter (about 36 ft) amplitude of motion.  If 
you are closer than 10 kilometers to the epicenter then this 
is some factor bigger.  None of these references talk about 
what happens when the whole tectonic plate moves.  The 
experts simply have no experience with it.
