Bob, how interesting that the very same question was a hot topic of 
debate in our house last night.  Did the DPRK really set off a nuke 
or did they just set off a chemical explosion to fool everyone?

I don't believe any but the closest seismometers would be able to 
discriminate between a nuke or a chemical explosion of M 4.2.  The 
rise time of a nuke versus a chemical explosion would be different 
but to discriminate between the two at any distance from the 
hypocenter might be difficult.  The modification of the initial 
P-wave by the country rock might make it even harder.

This is something the CTBTO and USAF AFTAC and nuke-watching network 
operators WOULD know.  :)

Bob Hammond
Public Seismic Network - Alaska
http://apsn.awcable.com



At 07:36 AM 10/9/2006, you wrote:
>According to the news, the US has not confirmed that a nuclear device was
>exploded, only that the event was equivalent to a large amount of TNT, but
>below the kilo-ton level, a normal measurement for nuclear explosions.
>
>Does anyone in the PSN group have any thoughts about the different in
>seismic signatures between a chemical and nuclear explosion.  I am wondering
>about the buildup of pressure that would generate the initial P-wave, and
>any differences in P-wave form that would be present between the chemical
>and nuclear explosions.  Also, how does the rate of expansion on the shock
>wave compare between chemical and nuclear explosions.
>
>Bob Hancock
>
>
>
>
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Bob Hammond
Public Seismic Network - Alaska
http://apsn.awcable.com

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