[meteorite-list] Seismic Data search for 6JUL09 meteor

From: Mr EMan <mstreman53_at_meteoritecentral.com>
Date: Wed, 8 Jul 2009 11:55:10 -0700 (PDT)
Message-ID: <30857.98364.qm_at_web55208.mail.re4.yahoo.com>

Thank you for stepping up and great work there Kelly on the elevation, I have a planetarium application on my computer but knocked off at 4am on trying to get an elevation based on a general Baltimore location on the evening and time in question.

Let me address several points in the broader area of having to rethink and rework traditional data collecting on fireballs in general and this one in particular.

Yes--there is some emerging data which points to a more SE-NW (as opposed to a E-W) trajectory than was indicated before. This could result in a fall/terminus back inside PA between Gettysberg and York. If so, this raises a caution against accepting at face value, the reliability of self-reported fireball reports. As I've mentioned before, a part of the science is an on site interview with the witness to refine their experience with simple tools and confirm their true orientation.

I believe seismic data can be used to reconstruct the trajectory/ground path even if the thump of a fall is not detected. Given that the US Air Force has now made satellite data classified, we need to find and validate other data sources which go untapped for fireball track information. This event lends itself to that validation.

I am working on another fireball for which seismic data is scant but shows two deviations. One consistent with the sonic boom arrival time and another approx 30 min later consistent with a fall from altitude arriving on the ground. These "spikes" are in the usual capture of events such as mine blasting, truck accidents, train couplings, etc. which seismologist have no reason to explore.

I know that sonic boom signatures were captured by seismometers as early as the 60's--I believe even for the Shuttle Orbiter's returns--They don't rise above the level of typical noise unless one matches them with the known time of the event across several stations. I believe the 9-11 towers collapsing rose to the level of earthquake energy, if memory serves.

I believe that in the normally captured --but normally discarded data, however weakly it is captured, is a scientifically valid signature of the ground track for fireballs such as these. In this case we have reports of sound energy so strong that houses shook and in one case a report of a pressure change within a house that included slapping open exhaust fan shutters. Be it remembered that in the old days of unrestricted supersonic flight over land the Air Force paid for a lot of cracked windows.

As to this PA/MD Event something with this much energy is going to show up on seismograms but the seismologist that review them won't recognize as such because they only think in the paradigm of things which are of earthquake energies. We need to get them thinking above the ground.

Finally, it takes weeks to put together a working team if you are within academia and more so if one request the data from the private sector. I hope someone with connections on the list might be able to get a seismologist interested in making a network inquiry-- For reasons unknown to me, there appear to be multiple seismic network arrays and affiliations that do not talk to each other.

Elton



--- On Thu, 7/9/09, Kelly Beatty <jkellybeatty at comcast.net> wrote:
> my take: this putative fall is unlikely to generate a
> seismic signal if pieces hit the ground at terminal free-fall velocity
> (several hundred mph for really large chunks, much less for smaller ones).
 meanwhile, I've analyzed Mike Hankey's photo. assuming the
> bolide was 1:10 am local time and "falling from the sky", as reports
> indicate, then the meteor segment in the image he took was centered at AZ 73?, AL 63??, and had a bearing toward the east-northeast horizon.
 
> clear skies,
> Kelly
>
> ****************
> J. Kelly Beatty
> Senior Contributing Editor
> SKY & TELESCOPE
> 617-416-9991
> SkyandTelescope.com
Received on Wed 08 Jul 2009 02:55:10 PM PDT