[meteorite-list] Norwegian fireball, seismics, etc.

[Marco Langbroek]

Ah, two days away from my e-mail and meanwhile the Norwegian Fireball story has 
evolved considerably, to more sane proportions.

As Chris noted, seismic records with large fireballs are not uncommon. Any 
fireball producing sonic booms is likely to register om seismographs, if they 
are in te area. A ground level impact really is not required, although the 
seismic trace of the latter would be different from those of an airburst.

Sterling: another nice case of a fireball with airburst strongly registering on 
a very large number of seismic stations was the June 3, 2004 fireball over 
Washington State (see http://orca.phys.uvic.ca/%7Etatum/fireball/). Rob Matson 
and me, and prof. Jeremy Tatum and a number of other people from the RASC worked 
on that one. From what we were able to glean from the trajectory and speed 
reconstruction (Rob's considerable work) and resulting approximate orbit (my 
modest work based on Robs work) that probably was a cometary object, perhaps 
related to P/Pons-Winnecke (see the collection of preliminary papers on the 
above URL).

Bjorn: if you have estimates by eyewitnessses of the apparent fall angle and 
direction as seen from several localities, I have a spreadsheet that can be used 
to yield an estimate of the entry angle and entry direction (azimuth) of the 
fireball, provided enough data is available.

About the brightness-size relation: that is a tricky thing. It is determined in 
  a rough way by object size, speed and entry angle: but in reality, the 
fragmentation history, material density/ablation properties etc. are of 
(considerable) influence too. I don't feel confident trying to make an estimate 
regarding this matter. The more as there are only very rough brightness 
indications anyway (I think the mag. -26 estimate is too high, the more as the 
sun was low in the sky)

- Marco

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Dr Marco Langbroek
Dutch Meteor Society (DMS)

e-mail: meteorites at dmsweb.org
private website http://home.wanadoo.nl/marco.langbroek
DMS website http://www.dmsweb.org
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