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North Korea Nuclear Test Causes 4.7 Mw Quake

Posted by feww on May 25, 2009

North Korea Nuclear Test Causes magnitude 4.7 Earthquake

FEWW can confirm with 0.95 certainty that the magnitude 4.7 North Korea earthquake that occurred near Chongjin  earlier today was caused by an underground nuclear test.

Based on FEWW estimates, the NK nuclear test had a blast yield of about 12 kilotons (TNT equivalent), or 50TJ  (50 x 10¹²J), almost similar to the first US atom bomb detonated above Hiroshima.

Earthquake Details
Magnitude: 4.7

Date-Time: Monday, May 25, 2009 at 00:54:43 UTC

Location:  41.331°N, 129.011°E
Depth: 0 km (~0 mile) set by location program [occurred at a shallow depth]

  • 75 km (45 miles) NNW of Kimchaek, North Korea
  • 95 km (60 miles) SW of Chongjin, North Korea
  • 180 km (110 miles) SSW of Yanji, Jilin, China
  • 380 km (235 miles) NE of PYONGYANG, North Korea

Location Uncertainty: horizontal +/- 5.3 km (3.3 miles); depth fixed by location program
Parameters: NST= 76, Nph= 76, Dmin=474.4 km, Rmss=0.8 sec, Gp= 68°,  M-type=body wave magnitude (Mb), Version=8
Event ID: us2009hbaf

Seismic Hazard Map [USGS]

NK SHM USGS us2009hbaf

Tectonic Summary: USGS says it cannot cannot confirm that the recent event was a nuclear test, however it says the quake was shallow and located in the vicinity of the October 2006 North Korean nuclear test.

Note: A magnitude 4.3 quake, which occurred in N. Korea on October 09, 2006  at 01:35:28 UTC, as recorded by USGS,  was centerd at 41.29°N, 129.09°E at a depth of 0km .

How did the energy yield compare with other nuclear detonations/ earthquakes?

1.  Hiroshima atom bomb had an energy  yield of about 63TJ, or 15 kilotons (TNT equivalent). [Note: Estimates vary between 12-18 kilotons.]

2. Fat Man, the atomic bomb detonated over Nagasaki, yielded about 88TJ of energy, the equivalent of 21 kilotons of TNT.

3. Sichuan earthquake, China, 2008, which left up to 90,000 people dead, was a magnitude 7.9 Mw, which released about 3.3 EJ of energy (3.3 exajoules), or the TNT equivalent of 0.71 gigaton. [ Note: Various sources reported quake magnitude at 7.8 to 8.0 Mw.]

4. Sumatra Earthquake, which caused the deadly 2004 tsunami, was a magnitude 9.2 earthquake with an estimated yield of about 91 billion tons (91 gigatons of TNT). [Note: The Sumatra earthquake has been reported at different magnitudes of 9.1 – 9.3 Mw.

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10 Responses to “North Korea Nuclear Test Causes 4.7 Mw Quake”

  1. […] testing are often used to detect nuclear explosions.  The recent detonation by North Korea was inferred through the use of seismic analysis.  Nuclear testing by Russia was also discovered through the use of seismic […]

  2. c080 said

    this was supposed to be added

  3. c080 said

    I have a theory , think of newtons pendulum .

    After the nuke test , possibly taking in account the size of the earth , could a nuke fired underground cause a reaction from the resistance of one side pulsate to the other for the same reaction , or even stronger effect.


  4. feww said

    New York Times, too, is desperate to downplay the blast yield from N-Korean nuclear test:

  5. feww said

    N Korea Nuke Test Confirms ‘GigaTrends’

  6. Rudy said

    Oh, wait, I see now the ‘caution’ on your page, that kills all discussion. Never mind my remarks.

  7. Rudy said

    It’s not about a previous record of geological faults or seismicity or geological stability, it’s about the amount of energy produced by the explosion that is converted into seismic energy. This varies greatly from one place to another, determined by the geological makeup (decoupling).

    If I’m wrong, then show a calculation that contains the seismic magnitudes of both test, resulting in your figure of 12 kilotons.

  8. Rudy said

    A yield of 12 kilotons seems to be too high. Note that the geological makeup of the test site has a big impact on the seismic tremor the detonation causes.

    We know that the first NK test was estimated by the US as “less than a kiloton”, and South Korea estimated it at 0.8 kilotons. We also know that the tremor in 2006 was 4.2 on the Richter scale, now it’s 4.7. We can calculate that the yield of the test today was about 0.8 x ( 10^(4.7-4.2))^(3/2) = 4.5 kilotons.

    • feww said

      Your entire argument is based on what we know to be a false premise, that the Bush Administration, contrary to their normal practice, issued a true statement regarding the yield of NK’s 2006 underground test.

      You also say “the geological makeup of the test site has a big impact on the seismic tremor the detonation causes.”

      However, the area appears to be geologically stable with no previous record of geological faults or seismicity. If in fact there were to be a compounding effect due to the faults or deformations in the testing ground, it would have manifested itself by way of additional aftershocks, of which there have been none reported.

      Based on all the information available, the Moderators believe their yield estimate of 12 kilotons to be fairly accurate.

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