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

From: Marco Langbroek <marco.langbroek_at_meteoritecentral.com>
Date: Thu Jun 15 13:38:40 2006
Message-ID: <44919B18.9010803_at_wanadoo.nl>

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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Received on Thu 15 Jun 2006 01:38:32 PM PDT