Hi ted -

Interesting - Following is my take - just that of another amateur.

Looking at it without spreading, I see an increase in amplitude that  
appears to start about 0732:55, and then a sharp increase in amplitude  
about 0737:11.  When I changed the X scale to 15 seconds, I see the  
large wave amplitude and overlaid on that is a smaller, higher  
frequency wave, possibly your background noise.

The thing that stands out to me is that I do not see any wave pattern  
that I recognize.  I have see many events where the P wave and  
sometimes the S wave are lost in the background noise - you appear to  
have moderate background noise.  The focal mechanism can also suppress  
the P & S waves.  However excluding all body waves (P, S, etc, etc,  
etc, etc) I don't see anything that looks like a Love or Rayleigh  
wave.  The sharpness of the onset at 0732:11 is not typical of either  
Love or Rayleigh wave, and again typically, their frequencies are much  
longer 15-30 seconds.  The Love wave is typically a large wave and on  
the transverse channel.  You will not see it on the radial or vertical  
channels.  In other words, if the signal is 90 degrees to the sensor,  
you will see Love waves, but no Rayleigh waves.  If the sensor is  
aligned with the incoming ray path of the event, you will not see Love  
waves, but will see Rayleigh waves.

In other words, in your location, Boise, ID, you will see Rayleigh  
waves from all the Transpacific teleseismic events, but no Love  
waves.  On events from the north such as the recent event North of  
Svalbard, you will see Love waves, but no Rayleigh waves.  If the  
event were to occur in Seattle, you would see both waves.

Another indicator is the frequency of the large waves.  Again  
typically, Love and Rayleigh waves have much longer frequencies that  
the 2 to 3 seconds that I see.  I am not saying absolutely because  
with a single station, you cannot orientate the direction the signal  
came from, but based upon everything that I see I would be hard  
pressed to call it an earthquake.

I looked at the frequency of the signal FFT (Linear), and found the  
frequency to be broad based.  When I used a notch filter to remove the  
all data from 0.4 to 1 hz, the signal was still there and very clear.  
I also played around with both high and low pass filter, and the  
bandpass filter.  Still nothing was recognizable

Summary -

The overall frequency is higher than would be expected for a seismic  
event.

The shape of the waves are not typical of seismic event waves.

I did not recognize any seismic waves.

Could it be wind - possibly, but without recorded weather to correlate  
the wind velocity with sensor activity, that becomes another had  
call.  If you feel that there is good correlation, then wind is a  
strong possibility, but that is call you must make.

Your seismogram extends for over 20 minutes past the sharp increase in  
amplitude at 0737.  When the seismogram ends, the base amplitude is  
still higher than when the seismogram begins.

There are a number of articles on the PSN web site about calibration.   
I would suggest that when you have time, you look at calibrating your  
instrument.  You are currently displaying milivolts, but if your had  
the instrument calibrated, you would have a much better idea of  
magnitude and then be able to compare that with nearby stations.

Ted - my apologies, I have written a lot of words, but really said  
nothing.  I guess the sudden onset and gradual decline in amplitude is  
what is catching my attention. Like I said earlier, if that matches  
the wind then that is probably the answer, if not, I am not certain  
what to say except something obviously excited your sensor - most  
likely something other than an earthquake, but I will leave that  
answer to you.

Cheers

Bob








On Mar 29, 2009, at 7:27 AM, tchannel wrote:

> Hi Folks, Today March 29th about 02:35am,MDT,  07:35utc, I recorded  
> an event.  At least it looks just like an earthquake, but I see  
> nothing posted for this time.   Did anyone record anything around  
> 07:35 utc?
> We had a large wind storm about that time, but I don't think its  
> weather related.
>
> Thanks, Ted

Hi ted =
- 

Interesting - Following is my take - =
just that of another amateur.

Looking at it =
without spreading, I see an increase in amplitude that appears =
to start about 0732:55, and then a sharp increase in amplitude about =
0737:11.  When I changed the X scale to 15 seconds, I see the large =
wave amplitude and overlaid on that is a smaller, higher frequency wave, =
possibly your background noise.

The thing that =
stands out to me is that I do not see any wave pattern that I recognize. =
 I have see many events where the P wave and sometimes the S wave =
are lost in the background noise - you appear to have moderate =
background noise.  The focal mechanism can =
also suppress the P & S waves.  However excluding all =
body waves (P, S, etc, etc, etc, etc) I don't see anything that looks =
like a Love or Rayleigh wave.  The sharpness of the onset at =
0732:11 is not typical of either Love or Rayleigh wave, and again =
typically, their frequencies are much longer 15-30 seconds. =
 The Love wave is typically a large wave and on the transverse =
channel.  You will not see it on the radial or vertical channels. =
 In other words, if the signal is 90 degrees to the sensor, you =
will see Love waves, but no Rayleigh waves.  If the sensor is =
aligned with the incoming ray path of the event, you will not =
see Love waves, but will see Rayleigh waves.

In =
other words, in your location, Boise, ID, you will see Rayleigh waves =
from all the Transpacific teleseismic events, but no Love waves. =
 On events from the north such as the recent event North of =
Svalbard, you will see Love waves, but no Rayleigh waves.  If the =
event were to occur in Seattle, you would see both =
waves.

Another indicator is the frequency of =
the large waves.  Again typically, Love and Rayleigh waves have =
much longer frequencies that the 2 to 3 seconds that I see.  I am =
not saying absolutely because with a single station, you =
cannot orientate the direction the signal came from, but based upon =
everything that I see I would be hard pressed to call it an =
earthquake.

I looked at the frequency of the =
signal FFT (Linear), and found the frequency to be broad based. =
 When I used a notch filter to remove the all data from 0.4 to 1 =
hz, the signal was still there and very clear. I also played around with =
both high and low pass filter, and the bandpass filter.  Still =
nothing was recognizable 

Summary =
-

The overall frequency is higher than would be =
expected for a seismic event.

The shape of the =
waves are not typical of seismic event waves.

I =
did not recognize any seismic waves.

Could it =
be wind - possibly, but without recorded weather =
to correlate the wind velocity with sensor activity, that =
becomes another had call.  If you feel that there is good =
correlation, then wind is a strong possibility, but that is call you =
must make.

Your seismogram extends for over 20 =
minutes past the sharp increase in amplitude at 0737.  When the =
seismogram ends, the base amplitude is still higher than when the =
seismogram begins.

There are a number of =
articles on the PSN web site about calibration.  I would suggest =
that when you have time, you look at calibrating your instrument. =
 You are currently displaying milivolts, but if your had the =
instrument calibrated, you would have a much better idea of magnitude =
and then be able to compare that with nearby =
stations.

Ted - my apologies, I have written a =
lot of words, but really said nothing.  I guess the sudden onset =
and gradual decline in amplitude is what is catching my attention. Like =
I said earlier, if that matches the wind then that is probably the =
answer, if not, I am not certain what to say except something obviously =
excited your sensor - most likely something other than an earthquake, =
but I will leave that answer to =
you.

Cheers

Bob








On Mar 29, 2009, at 7:27 AM, =
tchannel wrote:

Hi Folks, Today March =
29th about 02:35am,MDT,  07:35utc, I recorded an event.  =
At least it looks just like an earthquake, but I see nothing posted for =
this time.   Did anyone record anything around 07:35 =
utc?
We had a large =
wind storm about that time, but I don't think its weather =
related.
 
Thanks, =
Ted

=