According to the U.S. Tsunami Warning System, there is no threat of a tsunami from today's magnitude 7.2 earthquake in the Pacific 89 km southeast of Sendai, Fukushima Prefecture, Japan.
We hope that they are right as earthquakes of this size can trigger tsunamis. According to the Japan Meteorological Agency JMA, no tsunami should be expected either, only slight changes in sea level.
It is interesting to note that today's quake occurred in almost the same location as the catastrophic Tohoku earthquake from 11 March 2011. In fact, it is likely a late aftershock.