OK, while I was making the post on advancing the dates of future earthquakes, posting at http://www.earthwaves.org/wwwboard/messages/78589.html
in the last half hour, a M6.1 quake located at the trench at 30 deg N offshore Kyushu occurred. It was about 20 minutes ago. Maps are appearing now. The focal mechanism has not been put up yet. Because it is located at the trench (is this the Nankai trough?), and not downdip from it, it may be a normal slip quake (stretching in the ocean slab). The foreshock for the Honshu M9, the 7.2, was a thrust quake on the subduction zone if I recall correctly. So, if this proves to be the case, is less likely to be a foreshock of a subduction quake.

So, EQF suggested that lots of lives could have been saved if actions had been taken when the M7.2 foreshock occured. But, what actions, given that one could not know it was a foreshock (but that the subduction zone was having stresses modified)? What about now, for this one? The part of the subducting Phillipines Sea quake from the M6.1 to Tokyo is long and far enough from its northern limit near Tokyo to make a M9. The 20th century history is that this plate boundary farther north has gone in M8 (low 8) quakes in the 1940s. The Jim Mori USGS webcast had discussion that seismologists thought that the part that failed in the M9 could only go in M7.5s to 8s because that is what happened in the last 100 years, even though in 869 (?) there was a quake similar to the 2011 M9. I was a bit put off that seismologists would do that; that they would think, after Sumatra and recognizing that Cascadia has had M9 quakes, that they would not expect it was possible for Honshu. (Until tsunami deposits and drowned forests were recognized by Brian Atwater and others maybe 20 years ago, seismologists thought that Cascadia was creeping and not capable of a great quake).

But, it is not helpful to the Japanese to speculate now on another great quake (even though I am doing just that). The odds of a M8+ quake in any given month on this part of this Nankai subduction zone is likely only very slightly increased over what you expect from just the historic rate of such quakes.

But, one might think the Japanese would already be looking into backups to the backups for cooling systems for other nuclear plants. If they don't have it already, they might want to put in sea floor observatories (mainly of real-time monitoring of seismicity). There is a professor here in the heartland heavily involved in the drilling into Nankai trough and I imagine they already have downhole instruments. The drill ship was damaged in the tsunami, as it hot the bottom during the trough between waves (I think it was trying to leave the harbor in NE Japan.

Chris