San Onofre shutdown will mean tight electricity supplies

[FBaggins]

73. And that was in the analysis

That's why the inundation line was set at 20'. This is the "maximum credible threat" - and very likely includes the scenario you mention. The aleutians are probably the only thing (apart from larger catastrophes) that could create a tsunami that size at SONGS.

But more importantly... if we're going to rebut a statement that says there's little risk of a tsunami that endangers the plant, it isn't sufficient to hypothesize a wave that is just barely higher than the seawall... because the seawall is not the last line of defense. The generators aren't in waterproof vaults because it might rain... they're there in case the plant is flooded. The backup batteries aren't so much higher just because they like to get extra exercise carrying them up and down stairs... they're there because they back up the generators and if the generators were knocked out there's probably a reason. The portable generators that are even higher are there in case the previous lines of defense fail.

In short... it wouldn't be unreasonable to say that if SONGS were sitting on the Fukushima site... it wouldn't have been at all the same event (and that's clearly a tsunami well above the sea wall)

Recorded human history isn't very old in this region.

Sure... but it's long enough to compare areas where there are credible threats to seafront reactors from tsunami and where they would be much rarer.

As an example - you can have a significant mid-plate quake just about anywhere. But when we discuss areas that are prone to earthquakes, we don't include them.