I'm watching a news press briefing right now about the tsunami. It was triggered by an 8.1 earthquake several hundred km northeast of the northeastern tip of Hokkaido, the northernmost of the four major islands of Japan.
The earthquake was felt only mildly in Hokkaido and not at all in Tokyo; I wouldn't even have known about it except that I happened to check a news website before going to bed.
The threat is quite serious, and is being treated so, but at this particular moment the only reports of activity are in the 20-40cm range. That's big enough to create serious water coming onshore; they said that the height can be amplified two to ten times that when it hits land, depending on conditions.
All of the TV stations except the shopping channels (which probably run only canned material) have a map of Japan with flashing coastline covering most of Hokkaido and the eastern coast of Honshu all the way down from Tohoku, past Chiba and Tokyo down to about Nagoya. But they are saying that the size and threat are smaller down here.
We live high enough and far enough inland that we're in no danger, and neither are our friends, but there are plenty of people close enough to the coast to worry about.
The predicted time of the earliest arrival has come and gone for the northern part of the country with no major waves reported, but we're not out of the woods yet...
Someone (the head?) of the meteorological agency is giving a briefing at this moment...