PSN-L Email List Message

Subject: Re: Chelyabinsk
From: "David Saum" DSaum@............
Date: Sun, 17 Feb 2013 09:45:47 -0500 (EST)

> Subject: Re: Chelyabinsk
> From:    Geoff 
> Date:    Sat, 16 Feb 2013 22:35:11 +0000
> On 2013-02-15 17:14, Steinar Midtskogen wrote:
>> Does anyone know whether there are any seismic recordings of today's
>> meteor blast near Chelyabinsk?
> it is my bet that you need to review microbarograph recordings
> instead of seismic records to see that event since
> most of the energy was taken by the atmosphere.
> i dont know where to find such records.

I do not see the Chelyabinsk event on my microbarograph but
I am not quite sure when the event would show up at my location
near Washington, DC

Does anyone know how to predict infrasound travel times?

Here are my preliminary calculations.
The webcams show the event took place at about 9:26 local time on 2/15.
The great circle distance from Chelyabinsk to DC is 5498 miles
and the speed of sound is about 761mph. So the travel time is
about 5498/761=7.22hrs=7:13.  Arrival time at DC in Chelyabinsk time is
9:26+7:13=16:39.  Correcting to DC local time 16:39-11=5:39.  But my
AmaSeis microbarobraph display is in GMT, so correcting my local time
to GMT is 5:39+5=10:39 on 2/15.

However I do not see anything significant around
this time on my display.  I wonder if the infrasound travel time could
be significantly longer due to paths at higher altitudes?

Another question is the frequency band of the probable infrasound
signal.  My system has a .05 hz to 20 hz bandwidth, and I assume
that the Chelyabinsk signal that reached DC would be at the lower
end of this band.  Unfortunately the wind noise also peaks in this
band, and the wind started up at about 10:00.

Here is my current microbarograph helicorder display with 5 minute updates.
Wind is the primary noise and you can see my local wind conditions from
the Washington Reagan Airport weather about 10 miles away
When the wind is calm I can detect a nice microbarom peak at about .2 hz.


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