Hi ,  After Ed's suggestion on the infra sound possibility, I did some more
investigation
on the 'noise' spike when the  Molniya 1-67,  Russian  communications satellite
re-entered
above my location. (27th Jan 2000 at 14:50:28 UT).  I checked the professional
Seismometers
via an AutoDrm request,  and this  showed no event.  Then as the final check I
looked
at the magnet recordings form a  magnetic observatory some 900 km away.

Bingo, at the time of my observation there is a distinct spike in the magnetic
records at
14:50UT. All three  component's of the magnetic field showed  the effect. That data
is
available for the next week or so at:

ftp://ftp.ips.gov.au/asfc/data/mag/lea/rawdata/images/learaw.000127.gif

I cant explain what caused the effect but it looks very interesting against the
seismometer
recordings and the visual observation.

Arie



Ed Thelen wrote:

> I knew  a guy who lived under the landing pattern for Los Angles
> International air port.  He ran a garden gate type seismograph
> adjusted to about 20 seconds natural period.  He said that
> even though it was in a little shed in the back yard,
> the seismograph had to be carefully covered with a good box
> or he would be affected by planes flying low overhead.
>
> Could there have been an non-audible pressure wave from the
> fireball that pushed the boom  of the seismometer a tiny bit?
>
> I don't know if a shock wave from say 50 Km high event
> (presumably a very audible sharp step in pressure)
> gets converted to a slow rising pressure wave that
> humans don't hear at ground level.
>
> (I do know that a supersonic Hustler bomber flying at
>  say 30,000 feet makes a very audible window rattling
>  "BOOM" at ground level.)


_____________________________________________________________________

Public Seismic Network Mailing List (PSN-L)