I took a look at the Wikepedia article, and the description isn't a good 
match for what I'm seeing.  They describe whistlers as decending in 
frequency, but in the kilohertz range.  My signals are only audible in 
the time compressed audio files.  In real time, they start around 2 hz 
and decend from there.  Well below the audible range.

Larry


On 7/23/2011 7:53 PM, Bob McClure wrote:
> You may be picking up whistlers. See "Whistler (radio)" in Wikepedia.
>
> Bob
>
> On Sat, Jul 23, 2011 at 1:19 PM, Larry Conklin  > wrote:
>
>     I was looking over the data I recorded overnight from the 6.5
>     quake off Japan.  In the process I applied a band-pass filter (0.4
>     - 2.0 hz) to see what, if anything, would show up.  What showed up
>     were two strange "chirps" that are all but hidden in the noise.  I
>     wouldn't have noticed them except for the fact that the first
>     occurred a little before the arrival time of the S wave.  I don't
>     believe that they have anything to do with the quake.  But I have
>     no idea and no theory for what did cause them.
>
>     They are substantially identical, lasting for about a minute and
>     20 seconds each, and decending from around 2 hz to .4 hz.
>      (Hmmmm.... just noticed the obvious correlation with my filter
>     limits.)  Trouble is, without the filter, the signals are
>     indistinguishable in the overall background.  But, I made sound
>     files from both the filtered and unfiltered data, and the chirps
>     are obvious in both versions and sound virtually identical.  So,
>     the filter may be truncating the ends a little, but looks like it
>     is more or less a lucky fit to the data.
>
>     I'd be interested in whatever speculative explanations anybody may
>     have to offer.  My system is an SG sensor based on Larry's
>     electronics board, and the data was recorded from the high
>     frequency channel.  I've seen some similar artifacts in my data
>     before, but didn't recognize how odd they were.
>
>     If anyone is sufficiently curious, I'd be happy to e-mail them
>     copies of the filtered and unfiltered event file data, along with
>     the .wav files I made.
>
>     Larry Conklin
>     lconklin@............ 
>     __________________________________________________________
>
>     Public Seismic Network Mailing List (PSNLIST)
>
>     To leave this list email PSNLIST-REQUEST@..............
>      with the body of the
>     message (first line only): unsubscribe
>     See http://www.seismicnet.com/maillist.html for more information.
>
>

  
    
  
  
    I took a look at the Wikepedia article, and the description isn't a
    good match for what I'm seeing.  They describe whistlers as
    decending in frequency, but in the kilohertz range.  My signals are
    only audible in the time compressed audio files.  In real time, they
    start around 2 hz and decend from there.  Well below the audible
    range.  

    

    Larry

    

    

    On 7/23/2011 7:53 PM, Bob McClure wrote:
    
You
          may be picking up whistlers. See "Whistler (radio)" in
          Wikepedia.

          

          Bob

        

      
On Sat, Jul 23, 2011 at 1:19 PM, Larry
        Conklin <lconklin@............>
        wrote:

        
I was
          looking over the data I recorded overnight from the 6.5 quake
          off Japan.  In the process I applied a band-pass filter (0.4 -
          2.0 hz) to see what, if anything, would show up.  What showed
          up were two strange "chirps" that are all but hidden in the
          noise.  I wouldn't have noticed them except for the fact that
          the first occurred a little before the arrival time of the S
          wave.  I don't believe that they have anything to do with the
          quake.  But I have no idea and no theory for what did cause
          them.

          

          They are substantially identical, lasting for about a minute
          and 20 seconds each, and decending from around 2 hz to .4 hz.
           (Hmmmm.... just noticed the obvious correlation with my
          filter limits.)  Trouble is, without the filter, the signals
          are indistinguishable in the overall background.  But, I made
          sound files from both the filtered and unfiltered data, and
          the chirps are obvious in both versions and sound virtually
          identical.  So, the filter may be truncating the ends a
          little, but looks like it is more or less a lucky fit to the
          data.

          

          I'd be interested in whatever speculative explanations anybody
          may have to offer.  My system is an SG sensor based on Larry's
          electronics board, and the data was recorded from the high
          frequency channel.  I've seen some similar artifacts in my
          data before, but didn't recognize how odd they were.

          

          If anyone is sufficiently curious, I'd be happy to e-mail them
          copies of the filtered and unfiltered event file data, along
          with the .wav files I made.

          

          Larry Conklin

          lconklin@............

          __________________________________________________________

          

          Public Seismic Network Mailing List (PSNLIST)

          

          To leave this list email PSNLIST-REQUEST@..............
          with the body of the message (first line only): unsubscribe

          See http://www.seismicnet.com/maillist.html
          for more information.