There are two answers to this. First, in terms of how big the bomb was -- not so much. Here's one rather funny analysis from a Harvard expert:
I love the US Geological Survey.
TheyGÇÖve published lat/long (41.294-¦N, 129.134-¦E) and Mb estimates (4.2) for the North Korean test.
There is lots of data floating around: The CTBTO called it 4.0; The South Koreans report 3.58-3.7.
YouGÇÖre thinking, 3.6, 4.2, in that neighborhood. Seismic scales, like the Richter, are logarithmic, so that neighborhood can be pretty big.
But even at 4.2, the test was probablya dud.
Estimating the yield is tricky business, because it depends on the geology of the test site. The South Koreans called the yield half a kiloton (550 tons), which is more or lessGÇöa factor of twoGÇöconsistent with the relationship for tests in that yield range at the Soviet Shagan test site:
Mb = 4.262 + .973LogW
Where Mb is the magnitude of the body wave, and W is the yield.
3.58-3.7 gives you a couple hundred tons (not kilotons), which is pretty close in this business unless youGÇÖre really math positive. The same equation, given the US estimate of 4.2, yields (pun intended) around a kiloton.
A plutonium device should produce a yield in the range of the 20 kilotons, like the one we dropped on Nagasaki. No one has ever dudded their first test of a simple fission device. North Korean nuclear scientists are now officially the worst ever.
Of course, I want to see what the US IC says. If/when the test vents, we could have some radionuclide dataGÇömaybe in the next 72 hours or so.But, from the initial data, IGÇÖd say someone with no workable nuclear weapons (Kim Jong Il, I am looking at you) should be crapping his pants right now.
First the missile, then the bomb. Got anything else you wanna try out there, chief?
The second danger is that we have an incompetent, opportunistic President whose party is in danger of losing control of the legislative branch in the next month. We have a President who started a war against Iraq for god knows what reason.
The solution at this point is -- not to back this President -- but to put people in Congress who know something about warfare, international affairs, and have strong minds and good hearts.
Someone like Jim Webb.
[footnote: how big were the bombs used against Japan?]
You will see lots of variation in reporting as to how big the bombs were used against Japan. Here's one analysis--
A deterministic estimate of the nuclear radiation fields from the Hiroshima and Nagasaki nuclear weapon explosions requires the yields of these explosions. The yield of the Nagasaki explosion is rather well established by both fireball and radiochemical data from other tests as 21 kt [one kiloton equals the explosive power of 1,000 tons of TNT]. There are no equivalent data for the Hiroshima explosion. Equating thermal radiation and blast effects observed at the two cities subsequent to the explosions gives a yield of about 15 kt [at Hiroshima]. The pressure-vs-time data, obtained by dropped, parachute-retarded canisters and reevaluated using 2-D hydrodynamic calculations, give a yield between 16 and 17 kt. Scaling the gamma-ray dose data and calculations gives a yield of about 15 kt. Sulfur neutron activation data give a yield of about 15 kt. The current best estimates for the yield of these explosions are the following:
Hiroshima 15 kt
Nagasaki 21 kt
The outside limits of uncertainties in these values are believed to be 20 percent for Hiroshima and 10 percent for Nagasaki. [In other words, the Hiroshima bomb has an outside range of 12-18 KT, and the Nagasaki bomb an outside range of 18.9-23.1 KT.]