Specifically: nuclear testing released about 30 times more Cs-137 (in particular) than Fukushima, also mostly into the Pacific. An estimated 25 MCi [0] = 925 PBq, vs. 23-50 PBq [1].

[0] http://books.google.com/books?id=JLFX6EMPqBkC&pg=PA34

[1] http://www.pnas.org/content/109/16/5984.full

(copied from an older HN comment I wrote)

edit: Here's a paper [0] which measured Sr-89 and Sr-90 in seawater near Japan: they found a ratio of about 0.026 of Sr-90 : Cs-137 -- relatively little strontium. Their estimate for total Sr-90 released is 90-900 TBq, corresponding to Cs-137 release estimates of 3.5 - 35 PBq. The figures for Chernobyl [1] are 10 PBq and 85 PBq respectively -- that is, Chernobyl released 10-100 times more Sr-90 than Fukushima. The Sr-90 : Cs-137 ratio was even higher (0.63) for atmospheric weapons tests: 600 PBq Sr-90, 900 PBq Cs-137 [2].

edit2: Made a table:

               Sr-90 [PBq]  Cs-137 [PBq]  ratio  ref
    Fukushima  0.09 - 0.9   3.5 - 34      0.026  [0]
    Chernobyl  10	    85            0.12   [1]
    Weapons    590          930           0.63   [2]

[1] (large pdf) http://www.unscear.org/docs/reports/2008/11-80076_Report_200... (table 1, page 9)

[2] http://books.google.com/books?id=JLFX6EMPqBkC&pg=PA34

Aside: until Fukushima is well and truly contained, the possibility of something catastrophic happening is still present.

Probability theory defers to physics.

I'll agree with the part that earthquakes aren't independent events...

EDIT: "The opposite occurred in Turkey along the great North Anatolian fault. A large quake in 1939 sent stresses farther down the fault, triggering a 60-year series of quakes whose latest installment was the deadly Izmit earthquake of 1999. The stresses have risen in the crust near the city of Istanbul, and a quake there is now considered more likely. " - http://geology.about.com/library/weekly/aa022303a.htm

That the reactors are not contained, is not a separate event. It is cleanup that has not yet occurred.

You wouldn't say, "Well, I fell off my bike at 25mph on pavement, landing precisely on both kneecaps, which was highly improbable" and then say "the probability that my knee is bleeding is therefore lessened", would you?

Good for cocktail parties.