Hi Folks,    For those who are new to these subjects, here is my case =
study on a specific problem, and the group's advise which fixed it.  =
With my new station setup and running, the trace would get progressively =
noisier, starting at 11:00pm until 8:00am.
This noise was huge, the trace started out, looking like a pencil line =
and then,would progress to something like the teeth of a saw, so large =
it would almost touch the line above and below. As the room went back to =
day time temp, so did the trace quite down.
The garage, where it sat, has no heat and no drafts.  The temp in the =
garage, at night, would get to 40-50 and during the day 60's.

Because I had not finished my cover/box the sensor sat on the floor open =
to the air.  I was advised to build a box which would protect the sensor =
from air currents and thermos. So last night, temporarily, I  covered =
the sensor using two sawhorses and two blankets. The trace remained =
perfectly still all night

As a newcomer to these issues, I had no idea the importance of these =
enclosures.  I noticed if I waved my hand or made any  movements, which =
created air movement I would see a spike.  I did not realize that =
invisible air currents in the room, caused by the different in floor vs. =
air temperature, would cause huge noise.

Thanks for the guidance.

Q 1.  I understand that some people orient their sensor N/S others E/W,  =
Are the sensors ever oriented at a 45 degree angle between the two?

Q 2. What are the expectations of a Lehman sensor?  I know that depends =
on many factors, and not the lease of which is the quality of the =
sensor, and its environment, as well as the type and location of the =
events.  But just in general terms. The AS1, which is not a Lehman =
suggest one should be able to see 6.0m from several thousand mile away, =
or something like that.
The reason I ask, I do hear statements, both over and under my =
expectations.  Time will tell, but I wanted your opinions.

Cheers, Ted




----- Original Message -----=20
  From: ChrisAtUpw@..........
  To: psn-l@.................
  Sent: Wednesday, October 18, 2006 7:41 AM
  Subject: Re: Questions


  In a message dated 2006/10/18, gmvoeth@........... writes:


    Hello Ted;
    The file 061017.013725.ebgz.psn is way too noisy. The gain should be =
reduced
    to the point where noise is only +/- a few counts.

    This signal reminds me of the Hawaii quake I received but instead of =
getting any S wave I just got two "P" waves (Main event/aftershock) and =
what seemed
    to be followed by surface waves.


  Hi Geoff, Ted,

         This advice is not correct. Ted has a Lehman which senses the =
microseismic background of 0.5 to 15 microns amplitude as well as quake =
signals. Ted will want to sense longer period quakes which are a small =
fraction of this amplitude and to filter them out, so he needs the =
background to be at least 100 counts. =20

         Regards,








Hi Folks,    For =
those who are=20
new to these subjects, here is my case study on a specific problem, and =
the=20
group's advise which fixed it.  With my new station setup and =
running, the=20
trace would get progressively noisier, starting at 11:00pm until=20
8:00am.
This noise was huge, the trace started =
out, looking=20
like a pencil line and then,would progress to something like the teeth =
of a saw,=20
so large it would almost touch the line above and below. As the room =
went back=20
to day time temp, so did the trace quite down.
The garage, where it sat, has no heat =
and no=20
drafts.  The temp in the garage, at night, would get to 40-50 and =
during=20
the day 60's.
 
Because I had not finished my cover/box =
the sensor=20
sat on the floor open to the air.  I was advised to build a box =
which would=20
protect the sensor from air currents and thermos. So last night,=20
temporarily, I  covered the sensor using two sawhorses and two =

blankets. The trace remained perfectly still all night
 
As a newcomer to these issues, I had no =
idea the=20
importance of these enclosures.  I noticed if I waved my hand or =
made=20
any  movements, which created air movement I would see a =
spike.  I did=20
not realize that invisible air currents in the room, caused by the =
different in=20
floor vs. air temperature, would cause huge noise.
 
Thanks for the guidance.
 
Q 1.  I understand that some =
people=20
orient their sensor N/S others E/W,  Are the sensors ever oriented =
at a 45=20
degree angle between the two?
 
Q 2. What are the expectations of a =
Lehman=20
sensor?  I know that depends on many factors, and not the lease of =
which is=20
the quality of the sensor, and its environment, as well as the type and =
location=20
of the events.  But just in general terms. The AS1, which is not a =
Lehman=20
suggest one should be able to see 6.0m from several thousand mile away, =
or=20
something like that.
The reason I ask, I do hear statements, =
both over=20
and under my expectations.  Time will tell, but I wanted your=20
opinions.
 
Cheers, Ted
 
 
 
 
----- Original Message ----- 

  From:=20
  ChrisAtUpw@....... 
  
To: psn-l@.............. 
  
Sent: Wednesday, October 18, =
2006 7:41=20
  AM
  
Subject: Re: Questions
  

In a=20
  message dated 2006/10/18, gmvoeth@........... =
writes:


  Hello Ted;
The file 061017.013725.ebgz.psn is way too =
noisy.=20
    The gain should be reduced
to the point where noise is only +/- a =
few=20
    counts.

This signal reminds me of the Hawaii quake I received =
but=20
    instead of getting any S wave I just got two "P" waves (Main=20
    event/aftershock) and what seemed
to be followed by surface=20
  waves.

Hi Geoff,=20
  Ted,

       This advice is not =
correct.=20
  Ted has a Lehman which senses the microseismic background of 0.5 to 15 =
microns=20
  amplitude as well as quake signals. Ted will want to sense longer =
period=20
  quakes which are a small fraction of this amplitude and to filter them =
out, so=20
  he needs the background to be at least 100 counts. =20
  

      =20
  Regards,

       Chris =
Chapman=20