Jeffrey LewisYield Estimation Placeholder

It’s late, I am tired.  I’ve got the better part of a post done, but I’ll finish it in the morning.

Short version: don’t spend too much time estimating yield using the USGS Mb number.  It gives you only a very rough approximation and there are better ways for seismologists to do it.  Until then, it’s “several” kilotons or use a range.  A very big range.


  1. George William Herbert (History)

    (Cartman voice on)

    Waveforms! Wheh! Ah! Myh! Waveforms!

    (Cartman voice off)

  2. Gridlock (History)

    It’s “twice the size of previous blasts” or “half as powerful as the bomb dropped on Hiroshima” depending on which news service you watch. No doubt it was the size of 3/8ths of a London bus and could have filled 3 Olympic swimming pools too.

    I miss the days of news being informative.

    • Magpie (History)

      Pfff. They clearly created a mini-black-hole and are even now negotiating with extra-dimensional beings on some plumpy-nut shipments.

  3. Gregory Matteson (History)

    What is the sense of USGS censoring? They don’t show the seismograms of ‘suspected’ nuclear tests. The only people they’re hiding them from are the unwashed masses, i.e. the American public. The Japanese people, for example, got to see them both shown and explained in public.

  4. Melissa (History)

    How sloppy is it to take the estimations from the last test and double because the seismic activity was about double?

    • George William Herbert (History)

      Sloppy, and you want to go by magnitude, but that’s not grossly wrong.

      By magnitude something like 4x the last one. Sloppily.

    • Magpie (History)

      Old and busted: dirty bombs.

      The new hotness: sloppy bombs.

  5. Arrigo (History)

    Oh come on, stop blaming the USGS, they are only waiting for the Legal department to finish the health warnings like “calculated in a building where nuts are seen”, “bomb is hot”, “current results are not indicative of past or future performance”…

    The net yield was “enough to piss everyone off”, no more, no less.


  6. Gregory Matteson (History)

    I see a lot of confusion in the media between magnitude and energy. There is about a full magnitude, measured as an ‘earthquake’, between the 2006 test and the current one, with a great deal of uncertainty. This would be approximately 31.2 times the engergy, if we knew how the local geology affects the seismology, and if we had access to detailed seismograms at different frequencies, which could clue whether the first test was partially muffled. Partial muffling of the first test could have been accidental or trivially easy. My comments are based on the detailed lay description of test muffling in the May 1960 edition of The Bulletin of the Atomic Scientists. No link because I couldn’t readily work around their not letting me copy the link.

    • George William Herbert (History)

      The current technical term of art is “decoupling”.

  7. ulan (History)
    • Carey Sublette (History)


      The BGR is estimating 40 kT, but their reference yields for the first two tests are at the extreme high end of the estimated yield range.

  8. Moe DeLaun (History)

    This news may be long stale, but it points to unique challenges in understanding signatures in the Northeast Pacific:

    “…3) The yield of large explosions might be disguised by siting the explosion at a location that selectively defocuses energy towards continents where most seismic stations are located; 4) The Wake Island array provides very stable measures of yield; 5) A moderate underground nuclear explosion appropriately placed in a subduction zone (e.g., the Kuril-Kamchatka portion of the circum-Pacific arc) could escape detection by the existing conventional network of continental and island seismic stations; … 7) A significant number of earthquakes, unreported by the conventional world wide network of seismic stations, are located within the interior of the Northwestern Pacific Basin.”

    — “Hydrophone Investigations of Earthquakes and Explosion Generated High- Frequency Seismic Phases”

  9. Andrew Foland (History)

    Off topic (apologies) but topical…

    Question to ponder: under what circumstances might something like the Chelyabinsk meteorite trigger an accidental exchange?

    (Amusing historical question to ponder: would the answer have been different 25 years ago?)

    • Carey Sublette (History)

      I think there is going to be an very interesting and instructive tale to tell about how this event was processed by the Russian military.

    • Captain Ned (History)

      Yeah, Chelyabinsk isn’t exactly my first pick for the “right” Russian oblast for this to occur.

      One would hope that the instant YouTube uploads would be viewed as crowd-sourced intel by the Russian military. Seeing those makes it clear that that was an incoming rock.

      Even if a detection radar picked it up its speed (current estimate of 30 km/sec) should clearly have marked it as a meteoroid rather than an incoming warhead.

    • Eve (History)

      At 300 kilotons of energy, I’m glad that bolide was coming in shallow and was essentially a high airburst. Estimates are currently that it was 7000 tonnes in mass and 15 m across. There is such great potential for a mishap should people have itchy fingers on the football, let alone how a North Korean military would react if a bolide that big detonated in the upper stratosphere, or heaven forbid reach the ground. With the current situation, the Russian media certainly brewed up a few long stories and misinterpretations.

    • Eve (History)

      …and unfortunately North Korea does not crowd source…..

  10. Carey Sublette (History)

    Regarding that meteor explosion. What’s with all the dashboard-cam video you see in the coverage?

    An interesting explanation:

    • Captain Ned (History)

      Yeah, the whole concept of no-fault auto insurance coverage simply doesn’t work in Russia.

  11. Carey Sublette (History)

    NASA is now saying a 7000 ton object at 18 km/sec with an explosion in the hundreds of kilotons.

    Here is an excellent video showing the fragmentation, explosion event, and termination. The segment starts at about 0:37.

    BTW – I measure an entry angle of 15 degrees in multiple videos.

  12. Allen Thomson (History)

    > One would hope that the instant YouTube uploads would be viewed as crowd-sourced intel by the Russian military. Seeing those makes it clear that that was an incoming rock.

    Yes, I just got off the phone having a discussion about this and think that the Web with real-time traffic-cams, building-cams, not-quite-real-time phone-cams, dash-cams, security-cams etc. could be used as a stabilizing factor. Whether that will actually happen, alas, depends on the wisdom of the relevant officialdom.

    • Carey Sublette (History)

      I can certainly see this leading to renewed efforts at risk reduction in coming months and years.

  13. Cthippo (History)

    Something to keep in mind is that meteors come in all the time, like every day. When the first Vela satellites went up in the 50s to detect nuclear detonations they had a lot of false positives from detonating meteors that no one on the ground had ever noticed.

    Fast forward 50-60 years to today and I suspect that the folks at PVO Strany (Russian equivalent of NORAD) knew it was a meteor from it’s signature long before it was noticed on the ground.

    The biggest pointer for an actual nuclear attack is launch signatures, which of course would have been absent in the case of a meteor.

    The takeaway from all this is that a meteorite impact would be very unlikely to trigger a US / Russian nuclear exchange because both nations have systems to monitor the space environment and detect and classify objects hurtling towards the ground. They would know that it had not been launched from the other side, that it was moving too slow, and that it had the wrong signature when it detonated.

    The question becomes, what if it landed elsewhere? Does China or India, much less Pakistan or North Korea have the ability to determine it[i] wasn’t [/i] an attack when the first think they know is that they’re getting reports of a huge detonation over their territory? Would NORAD or PVO Strany pick up the phone and call the national leader and let them know what just happened? Would they be able to get the message to the right person in time even if they tried? This is the scenario I see where an event of extra-terresterial origin could trigger a limited nuclear exchange before either side figured out what happened.

    Fortunately, big rocks don’t fall out of the sky and flatten cities often enough for me to lose sleep about it, but I can see how it could have further consequences.

    • Carey Sublette (History)

      Certainly it seems unlikely that an incident like this is going to result in rash and regrettable action, there is a substantial and troubling literature showing the faults of strategic data collection and command and control systems in the past to make this a matter of continuing concern. The extreme potential consequences of error mean that relatively low probability events must be given considerable weight.

      The implicit assumption that all sources of data are collected, integrated, analyzed and distributed effectively in near-real-time is problematic. In this case we have an (at last report) a atmospheric detonation of up to 500 kilotons(!), the same size as a typical strategic warhead exploding over a military city devoted to nuclear weapons production.

      Staff involved tracking the object coming in may realize it is not a warhead, but independent nuclear detonation detectors may not reveal that fact and might be passed to parties without being integrated with the tracking data.

      There is also a vast literature about how organizations and individuals can fail to correctly interpret information due to biases introduced by their expectations or interests, at times in glaring contradiction to the evidence (the Yom Kippur War surprise, TMI, the Bush economic Crash, to name but a few).

  14. Captain Ned (History)


    I worry some in this vein WRT Russia and China, but the true scare to me is the Norks. If this had happened over Pyongyang or any of their nuclear or missile facilities I shudder to think what Seoul would look like right now.