Do The Continents Move? how can an earthquake be felt over an entire continent?

If you are referring to the earthquake that occured on
08/24/2011 then the answer is actually very simple.

Due to
the fact that the continental plate in which the eastern coast of the united states is
made of is older it therefore means it is also more dense (solid). Seismic waves as we
have learnerd through scientific study that the plates that are denser allow waves to
move faster and those that are less dense such as the asthenosphere causes waves to slow
down due to decrease in density. In other words the energy cannot move from one particle
to the next because they are not touching as closely. Because of all of the above the
east coast allows seismic waves to travel much farther and faster and lose very little
energy in the process. Where in the west coast lets say anything west of the rockies the
plate is a bit newer and less dense.