From: Steinar Midtskogen 
To: psnlist 
Sent: Wed, 20 Feb 2013 20:12
Subject: Re: Chelyabinsk


Yes, as someone said, it's an atmospheric event, but isn't there a
possibility that geophones could pick that up?  The infrasound will
make the ground shake, but I'm not sure if that would happen 1000+ km
away from an event like this.

My geophones are 3000 km away, but unfortuneatly the arrival of the
infrasound occurred precisely at the time of the morning activity in
our house, so even if there is a weak signal there, it's hard to find
because of local noise.

Hi Steinar,

    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.

    Regards,

     Chris Chapman
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