A few years ago, I wrote a program regarding the travel times of infrasound.

It turns out the wave propagation is rather complex. The earths atmosphere
has different densities, chemical differences and wind's.

The final program with a travel time "text data" was never completed but the
graphical interface was.

I just ran a simulation with the sound source at 10km above the earth.
The graphical representation can be found at http://www.geosn.com
or http://geosn.com

The Y axis is the height above the ground and the X axis the distance
 from the source. 5 different angle's were plotted.

Maybe I should finalize the program ? With text data and realistic pressure
values.

Anyhow, for your interest. It should give good idea on how the infrasound
propagates.

Cheers Arie



On Sun, 17 Feb 2013 22:45:47 +0800, David Saum  wrote:

>> 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.
> http://www.infiltec.com/Infrasound@..............
> Wind is the primary noise and you can see my local wind conditions from
> the Washington Reagan Airport weather about 10 miles away
> http://w1.weather.gov/obhistory/KDCA.html
> When the wind is calm I can detect a nice microbarom peak at about .2 hz.
>
> Dave
> http://www.infiltec.com/Infrasound@home
> http://www.infiltec.com/seismo/qm45.htm
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