Descriptions from the USGS on motion amplitude state that in earthquake magnitudes and
intensity we find a magnitude 5 earthquake at about 10 kilometers from the epicenter to be 1.1
millimeters of motion. If we use the increase by 10x for each one magnitude change, then for
magnitude 9 earthquake we would get 11 meters (about 36 ft) amplitude of motion. If you are
closer than 10 kilometers to the epicenter then this is some larger factor. None of these
references talk about what happens when the whole tectonic plate moves. The experts simply
have no experience with it.
Offered by Mike.