In a message dated 02/01/2010 05:38:06 GMT Standard Time,  
rsparks@.......... writes:

I took a  look before and after the quake but did not see anything unusual. 
  

Not unusual for this location is to have a fuzzy trace (~1 Hz High  Pass) 
beginning about 0630 and ending about 1700 local times.  Since I am  using a 
vertical, I have attributed this to the sun warming the  atmosphere.  But, 
the noise does not seem to be present during non-work  days which is 
completely inconsistent with a solar source.  I live about  2 miles from any serious 
auto traffic which would be on I-90 in Central  Washington.  I have no 
explanation for this "fuzz"

Hi Roger,
 
    You do get increased atmospheric noise after dawn.  Uncompensated 
verticals sense atmospheric noise only too well. I presume that  your vertical 
has no pressure compensation? 
    If the noise is not present on non working days,  what is the heating 
profile of the house? This sounds more like some sort of air  convection 
noise.
    Is the seismometer case sealed at the edges and  over the top? Have you 
tried draping it with a large sheet of bubble wrap with  the bubbles inside 
and the sheet folded downwards at the corners?

The  "fuzz" is not visible with either the all pass or low pass filters in  
place.
    How does the all pass filter modify the output? I  would not have 
expected it to.

One  puzzle here is that in the past I could get a fairly clean FFT peak at 
about 6  seconds and little at longer periods.  Lately, I notice a broader 
peak at  6 seconds and a second peak as low as 44 seconds (both very broad  
peaks).  I took a look at about 4 hours of data a few moments ago and  
confirmed what I had previously found.  

    My other question is what sort of suspension  systems are you using? 
Could there be noise generated at the spring  fastenings? 
    Does replacing the first opamp in your amplifier  change the signals 
that you see?
 
    Regards,
 
    Chris Chapman





In a message dated 02/01/2010 05:38:06 GMT Standard Time,=20
rsparks@.......... writes:
I took a=20
  look before and after the quake but did not see anything unusual. =
=20
  

Not unusual for this location is to have a fuzzy trace (~1 Hz Hi=
gh=20
  Pass) beginning about 0630 and ending about 1700 local times.  Sinc=
e I am=20
  using a vertical, I have attributed this to the sun warming the=20
  atmosphere.  But, the noise does not seem to be present during non-=
work=20
  days which is completely inconsistent with a solar source.  I live=
 about=20
  2 miles from any serious auto traffic which would be on I-90 in Central=
=20
  Washington.  I have no explanation for this "fuzz"

Hi Roger,
 
    You do get increased atmospheric noise after=
 dawn.=20
Uncompensated verticals sense atmospheric noise only too well. I presume=
 that=20
your vertical has no pressure compensation? 
    If the noise is not present on non working da=
ys,=20
what is the heating profile of the house? This sounds more like some sort=
 of air=20
convection noise.
    Is the seismometer case sealed at the edges=
 and=20
over the top? Have you tried draping it with a large sheet of bubble wrap=
 with=20
the bubbles inside and the sheet folded downwards at the corners?
The=20
  "fuzz" is not visible with either the all pass or low pass filters in=20
  place.
    How does the all pass filter modify the outpu=
t? I=20
would not have expected it to.
One=20
  puzzle here is that in the past I could get a fairly clean FFT peak at=
 about 6=20
  seconds and little at longer periods.  Lately, I notice a broader=
 peak at=20
  6 seconds and a second peak as low as 44 seconds (both very broad=20
  peaks).  I took a look at about 4 hours of data a few moments ago=
 and=20
  confirmed what I had previously found.  

    My other question is what sort of suspension=
=20
systems are you using? Could there be noise generated at the spring=
=20
fastenings? 
    Does replacing the first opamp in your amplif=
ier=20
change the signals that you see?
 
    Regards,
 
    Chris Chapman