Mark 13:8 For nation shall rise against nation, and kingdom against kingdom: and there shall be earthquakes in divers places, and there shall be famines and troubles: these are the beginnings of sorrows.

Note: "...earthquakes in divers places..." (diverse, or MANY places)

Major earthquakes in MANY places will be a much more common occurrence the closer we get to the return of the Lord.

So far as martial law, I doubt we will see it resulting directly from the Japan event. Riots over economic effects or earthquakes in the US will bring it on pretty quickly. And, they are not far off.