We felt a tiny quake in central Tokyo (2, maybe a 3), but we didn't see any Tsunami alert. Anything less than a strong 5 (Japanese scale) really doesn't phase me anymore.
Anyway, for the guy coming to Japan, nothing really to worry about. I guess it depends on your mode of transportation to get up north. As of today, everything is running on a normal schedule.
When a quake does it, depending on the size, trains may pause for a few moments and then resume if there's no immediate danger. I know a lot of people hop a Shinkansen from either Tokyo or Ueno to go north... others use buses.
Nartia is further than Haneda of course, but only about 1 hour on average by train. I live a stones throw from Haneda, but it still takes me almost an hour to get there. (Tokyo Monorail, needs to be updated or replaced...) For Narita, I use a train called the Skyliner from Ueno station and it takes me a total of 1 hour 15 minutes from my door to the departure terminal at Narita.