On 3/5/2013 5:01 PM, chrisatupw@....... wrote:
> From: Steinar Midtskogen 
> To: psnlist 
> Sent: Fri, 22 Feb 2013 7:13
> Subject: Re: Chelyabinsk
>
>
> Hi Chris,
>
>>    The CTBT web site shows a broad spectrum of waves up to well over
>> 3 Hz. I would have expected there to be some pressure wave signals
>> showing up on your Lehman, but they would have arrived well before the
>> sound signal. Did you check ? A 1 Hz geophone, or an extended range
>> 4.5 Hz geophone might have shown something.
>
> I only checked my 4.5 Hz geophones, since I would expect that
> frequency to be closer to what to expect than the range of the Lehman.
> So I just checked the Lehman.  What I have is moderately noisy,
> probably due to windy condition on the west coast of Norway 500 km
> away.  There's nothing standing out, except one blip at 06:31UTC.
>
> http://norskmeteornettverk.no/bilder/seismo_20130215.jpg
>
> I was looking for something lasting a little while, not something sub
> second, but on the other hand I have no idea what to expect from a
> fireball event.  The geophones do not have this blip at the same time.
>
> I think the meteor event happened at 03:22UTC (but I've seen various
> statements).  The distance is roughly 3000 km.  So 06:31UTC seems much
> to late anyway.  If the Lehman is sensitive to small barometric
> changes, such blips are more likely caused by someone opening or
> closing a door elsewhere in the house, I presume.
>
> Hi Steinar,
>
>    My apologies for the delayed reply - I have been visiting my other
> house for maintenance ~ 220 km away.
>     A Lehman is hardly effected at all by barometric changes, but can and
> will pick up horizontal vibrations like slamming a door.
>     The P wave velocity is about 6 km / sec for near surface and about 
> 8 km
> / sec for mantle waves. A 3000 km track could be expected to take about 6
> to 9 miutes, so you should look at 03.28 to 03.31 UTC for direct seismic
> signals. Atomic weapons produce quite a large signal, even air blasts, 
> but
> like earthquakes, only seismic frequencies below ~2 Hz are likely to be
> propagated.
>    I hope that this will help !
>
>    Regards,
>
>     Chris Chapman
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>

When meteors streak over head some people
seem to hear a hissing sound of noise
which would be high frequencies but
no one is reporting such a sound from this event ??

Regards,
geoff

-- 
*************
It is by the Entropy that I set my mind in motion.
Entropy is the seeking of equilibrium.
It is by the Entropy that I set my mind in motion.

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