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
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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 over=
night from the 6.5 quake off Japan. =A0In the process I applied a band-pass=
 filter (0.4 - 2.0 hz) to see what, if anything, would show up. =A0What sho=
wed up were two strange "chirps" that are all but hidden in the n=
oise. =A0I wouldn't have noticed them except for the fact that the firs=
t occurred a little before the arrival time of the S wave. =A0I don't b=
elieve that they have anything to do with the quake. =A0But 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. =A0(Hmmmm.... just noticed =
the obvious correlation with my filter limits.) =A0Trouble is, without the =
filter, the signals are indistinguishable in the overall background. =A0But=
, I made sound files from both the filtered and unfiltered data, and the ch=
irps are obvious in both versions and sound virtually identical. =A0So, the=
 filter may be truncating the ends a little, but looks like it is more or l=
ess a lucky fit to the data.





I'd be interested in whatever speculative explanations anybody may have=
 to offer. =A0My system is an SG sensor based on Larry's electronics bo=
ard, and the data was recorded from the high frequency channel. =A0I've=
 seen some similar artifacts in my data before, but didn't recognize ho=
w odd they were.





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



Larry Conklin

lconklin@........
r.com

__________________________________________________________



Public Seismic Network Mailing List (PSNLIST)



To leave this list email PSNLIST-REQUEST@.............. with the body of the m=
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See h=
ttp://www.seismicnet.com/maillist.html for more information.