Hello,

i used spectrograms many times.
I confirm that GRAM from Richard Horne is very well made
fast and reliable.

I applied a FFT for both graph and spectrograph JTF to seismowin
it can be used also for noise comparison with the Peterson's noise curve
widely recognized as a standard noise model.

People using DATAQ board could benefit of this seismowin's tool.

www.infoeq.it

regards
Mauro Mariotti

At 16:53 25/02/2005, you wrote:
>I have used this program before.
>http://www.visualizationsoftware.com/gram.html
>  It used to be free but you can still find older free versions on 
> download sites.
>
>Jim Hannon
>
>
>---------- Original Message ----------------------------------
>From: John or Jan Lahr 
>Reply-To: psn-l@..............
>Date:  Fri, 25 Feb 2005 07:19:42 -0800
>
> >
> >
> >Hi Jack,


> >We used "spectrograms" of the sort that you described in
> >studying the 1989-1990 eruption of Mt. Redoubt, Alaska.  They were
> >the best method that we found to monitor and distinguish "LP"
> >events (with emergent arrivals and lower frequency content) from
> >"VT" events (volcano-tectonic events with higher-frequency
> >content and sharp arrivals).  Swarms of LP events tended to precede
> >eruptions.


> >It would be great to have a tool available to amateur seismologists and
> >educators that would allow spectrograms to be easily generated.  Do
> >you think this could be done without the use of Matlab?


> >Cheers,

> >John


> >
>--
>Jim Hannon
>http://www.fmtcs.com/web/jmhannon/
>42,11.90N,91,39.26W
>WB0TXL
>--
>
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