A number of people emailed today about the tsunami, including their concerns about radioactivity from Japan reaching the Northwest.
It turns out that the leading national research center for tsunamis is here in Seattle (National Center for Tsunami Research). At the Center they have developed numerical simulation models for tsunami events.
Here is a simulation of the unfolding of this event (click on it to enlarge):
You see how complicated the structure is? Multiple waves, reverberating off obstacles in the basin and refracting around islands.
Here is the maximum tsunami amplitude map there produced:
The largest amplitudes were near Japan of course, but significant amplitude propagated thousands of miles away. This predictions suggested northern CA would get hit harder than us and it was correct.
At Crescent City the observed maximum tsunami amplitude reached nearly 7 ft, while the NW coast only saw .5 to 1.5 feet. Impressive prediction.
Tsunamis...known as "harbor waves" is Japan...are produced when earthquakes cause a displacement of a water volume in the ocean. This generates waves that can move at tremendous speeds over deep water.... as a jet aircraft! Amazingly, the passage of a tsunami wave over the deep ocean is nearly imperceptible.
But bad things happen when the wave approaches a coastal zone. The propagation speed of the wave decreases when the water becomes more shallow and the water converges and rises, producing huge waves that can reach 30 feet or more.
Often the water level falls prior to the arrival of the tsunami wave, luring the curious on to the beach. Bad idea. If you see a sudden retreat of the water, RUN as fast as you can to higher ground.
Not only do we have truly excellent simulation models of tsunamis, but we have much better data on water height as well. Specifically, there has been an increase in the number of DART tsunami buoys. The number of DART buoys (see graphic below for map) was greatly increased after the Indonesian tsunami, with some of our local legislators (particularly Congressman Jay Inslee) playing an important role.
Here is the data from the Dart buoy near Hawaii. You can see the regularly varying tidal variations during the previous days, and the major changes during the last day due to the tsunami.
Regarding radioactive release in Japan, nothing to worry about. Even if there was a MASSIVE release there, it would be utterly diluted by the time it reached us.