PSN-L Email List Message

Subject: Re: Metods for Improving SNR for events ??
From: "Connie and Jim Lehman" lehmancj@...........
Date: Sun, 17 Sep 2006 19:41:13 -0400


Jerry--improving SNR is always an ongoing effort in amateur as well as =
professional seismology.  In my day of recording we worked with passive =
filters to take out 60 hz and mechanical noise from climate control =
chillers, etc.  As long as microseisms were evident, we knew the system =
was working.  Here in Virginia we are entertained by variations in =
microseisms from day to day, sometimes hour to hour--hurricanes hitting =
Florida and moving up the coast.  Winter storms coming from Tennessee =
eastward to the coast, highs & lows in barometic readings, etc.  For =
some unexplained reason, microseismic amplitudes were generally low in =
May to August--we could almost double the gain of amplification--
   You speak of your systems on a concrete floor of a garage.  I do not =
know your location, but here in VA we ran a long period system under =
those conditions where temperatures varied as much as 30 degrees F. from =
day to night.  Not only do componets of the sensor respond, but concrete =
has an amazing way of microscopic shrinking and expanding, and these =
appeared as periodic peaks or snaps on the record.  Winds are frequently =
with us, and if trees are within several hundred feet of your sensor, =
the crowns are stressed by wind and this stress is transferred to the =
root systems and propagated to the sensor.
   I know there are active filters out there now that work wonders in =
minimizing noise--but I still find myself looking at the microseisms =
before and after an event to give me a frame of reference on the event.
  A good day to all              Jim Lehman
  ----- Original Message -----=20
  From: Jerry Payton=20
  To: PSN-L=20
  Sent: Sunday, September 17, 2006 11:00 AM
  Subject: Metods for Improving SNR for events ??


  Is there a way or ways to improve the SNR (signal to noise ratio) of =
an incoming event? =20

  I realize that if the incoming rays are not strong enough, they will =
not overcome the ambient noise of the system.

  I would further assume that lowering the ambient noise is the best =
solution, but I understand that can be a real challenge.  Personally, I =
live in a wooded area, remote from vehicle travel and most man-made =
noises.  But, weather and wind will affect my noise =
significantly......something I have to live with.

  My vertical and horizontal sensors are simply laying on a concrete =
floor in an unattached garage with proper covers over each.  Any gain =
adjustments raise or lower the noise factor directly.  I guess that =
finding a "happy level" and living with it is my only solution.  But, if =
there are any suggestions or remedies out there, I'd appreciate knowing =
about it..

  Best Regards,
  Jerry Payton=20







Jerry--improving SNR is always = an ongoing=20 effort in amateur as well as professional seismology.  In my day of = recording we worked with passive filters to take out 60 hz and = mechanical=20 noise from climate control chillers, etc.  As long as microseisms = were=20 evident, we knew the system was working.  Here in Virginia we are=20 entertained by variations in microseisms from day to day, sometimes hour = to=20 hour--hurricanes hitting Florida and moving up the coast.  Winter = storms=20 coming from Tennessee eastward to the coast, highs & lows in = barometic=20 readings, etc.  For some unexplained reason, microseismic = amplitudes were=20 generally low in May to August--we could almost double the gain of=20 amplification--
   You speak of your = systems on a=20 concrete floor of a garage.  I do not know your location, but here = in VA we=20 ran a long period system under those conditions where temperatures = varied as=20 much as 30 degrees F. from day to night.  Not only do componets of = the=20 sensor respond, but concrete has an amazing way of microscopic shrinking = and=20 expanding, and these appeared as periodic peaks or snaps on the = record. =20 Winds are frequently with us, and if trees are within several = hundred feet=20 of your sensor, the crowns are stressed by wind and this stress is = transferred=20 to the root systems and propagated to the sensor.
   I know there are = active=20 filters out there now that work wonders in minimizing noise--but I still = find=20 myself looking at the microseisms before and after an event to give me a = frame=20 of reference on the event.
  A good day to=20 all           &nbs= p; =20 Jim Lehman
----- Original Message -----
From:=20 Jerry = Payton=20
To: PSN-L
Sent: Sunday, September 17, = 2006 11:00=20 AM
Subject: Metods for Improving = SNR for=20 events ??

Is there a way or ways to improve the SNR (signal to noise ratio) = of an=20 incoming event? 
 
I realize that if the incoming rays are not strong enough, they = will not=20 overcome the ambient noise of the system.
 
I would further assume that lowering the ambient noise is the = best=20 solution, but I understand that can be a real challenge.  = Personally, I=20 live in a wooded area, remote from vehicle travel and most man-made=20 noises.  But, weather and wind will affect my noise=20 significantly......something I have to live with.
 
My vertical and horizontal sensors are simply laying on a = concrete floor=20 in an unattached garage with proper covers over each.  Any gain=20 adjustments raise or lower the noise factor directly.  I guess = that=20 finding a "happy level" and living with it is my only solution.  = But, if=20 there are any suggestions or remedies out there, I'd appreciate = knowing about=20 it..
 
Best Regards,
Jerry Payton

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