Subject: Re: Mount Hood... From: Bob Fryer bfryer@............ Date: Sun, 30 Jun 2002 12:31:54 -0700 Hello Kareem, I live west of Portland, Oregon, about the same distance from Mt St Helens and Mt Hood. We've been ashed... I witnessed several of the 1980 eruptions. Mt Hood has a history of erupting after Mt St Helens, according to some sources. Mt Hood last erupted just 200 years ago. Episodes like this have occurred several times in the last few years, at several locations on the South side of the mountain. This sequence is about 3 miles SSE of the summit. It has slowed considerably. See yesterday's activity at: http://www.ess.washington.edu/SEIS/PNSN/WEBICORDER/TDH_EHZ_UW.2002062912.html See today's activity at: http://www.ess.washington.edu/SEIS/PNSN/WEBICORDER/TDH_EHZ_UW.2002063012.html There are live fumaroles high on the mountain, about 800 feet below the summit. You could see the gases venting in the videos taken a few weeks ago at the site of a fatal climbing accident, and the helicopter crash which occurred during the rescue operations. While I knew of the fumaroles, I had never 'seen' them; I was startled by the level of activity. I don't know if this activity level was unusual. See the USGS Cascades Volcano Observatory (CVO) at: http://vulcan.wr.usgs.gov/ Early this May, I talked for several hours with Drs. Rauscher and van Bise who predicted the eruption of Mt St Helens, and many earthquakes over the past 20 years. They said they detected signals from St Helens in October or November of 1979, months before geophysicists were surprised by the early eruptive events. (You can see information about them on my website. Look at the bottom of this post. I will be adding information about their work.) Take care, Bob Fryer >What's everyone's guess about Mt. Hood in Oregon or have you been >following? There have been a remarkable number of quakes near the >cone. Yesterday morning's swarm started with a M4.8 bang and it was >followed by at least forty aftershocks. > >Is she telling us something? > >Kareem -- earthquake WARNING research Animals, People, Scientific Evidence www.earthquakewarning.org __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Mount Hood... From: "kArEEm" temp@............. Date: Mon, 1 Jul 2002 06:40:26 -0700 I knew someone would know the history of Mt. Hood; that's why I mentioned it. Thanks for the background info. -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Bob Fryer Sent: Sunday, June 30, 2002 12:32 PM To: psn-l@.............. Subject: Re: Mount Hood... Hello Kareem, I live west of Portland, Oregon, about the same distance from Mt St Helens and Mt Hood. We've been ashed... I witnessed several of the 1980 eruptions. Mt Hood has a history of erupting after Mt St Helens, according to some sources. Mt Hood last erupted just 200 years ago. Episodes like this have occurred several times in the last few years, at several locations on the South side of the mountain. This sequence is about 3 miles SSE of the summit. It has slowed considerably. See yesterday's activity at: http://www.ess.washington.edu/SEIS/PNSN/WEBICORDER/TDH_EHZ_UW.2002062912 ..html See today's activity at: http://www.ess.washington.edu/SEIS/PNSN/WEBICORDER/TDH_EHZ_UW.2002063012 ..html There are live fumaroles high on the mountain, about 800 feet below the summit. You could see the gases venting in the videos taken a few weeks ago at the site of a fatal climbing accident, and the helicopter crash which occurred during the rescue operations. While I knew of the fumaroles, I had never 'seen' them; I was startled by the level of activity. I don't know if this activity level was unusual. See the USGS Cascades Volcano Observatory (CVO) at: http://vulcan.wr.usgs.gov/ Early this May, I talked for several hours with Drs. Rauscher and van Bise who predicted the eruption of Mt St Helens, and many earthquakes over the past 20 years. They said they detected signals from St Helens in October or November of 1979, months before geophysicists were surprised by the early eruptive events. (You can see information about them on my website. Look at the bottom of this post. I will be adding information about their work.) Take care, Bob Fryer >What's everyone's guess about Mt. Hood in Oregon or have you been >following? There have been a remarkable number of quakes near the >cone. Yesterday morning's swarm started with a M4.8 bang and it was >followed by at least forty aftershocks. > >Is she telling us something? > >Kareem -- earthquake WARNING research Animals, People, Scientific Evidence www.earthquakewarning.org __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Integration and Winquake From: John Hernlund hernlund@............ Date: Mon, 01 Jul 2002 16:18:23 -0700 In practice, the FFT can be used to very easily obtain the integral or derivative of a time series (i.e. division or multiplication of all spectral points by i*frequency respectively). Since this is already built into Winquake, this would be the most efficient method, and is the one I always assumed was being used by Winquake. In this case there is no finite integration step, since the FFT is a sinusoidal fit, which is then played with. Randall Pratt wrote: >Arie, > >I don't have an answer but I have wondered about this also. I've considered >summing as you thought and also the possibility of maybe trapazoidal areas >with several points. Another question I have is how the result can begin at >other than zero displacement with a velocity sensor and zero time at file >start? I wonder if the algorithym starts in the middle or from some average >point and works to the ends? > >Randy > >----- Original Message ----- >From: "Arie Verveer" >To: >Sent: Tuesday, June 25, 2002 6:28 AM >Subject: Integration and Winquake > > > > >>Hi, Just a small question; When integrating data with Winquake >>does anyone now the integration period.? I would assume the integrated >>value is the sum of the y values times 1/ ( sample rate ) over the length >>of the integration period? . I'm probably wrong, any idea's. >> >> >>Cheers >> >>Arie >>__________________________________________________________ >> >>Public Seismic Network Mailing List (PSN-L) >> >>To leave this list email PSN-L-REQUEST@.............. with >>the body of the message (first line only): unsubscribe >>See http://www.seismicnet.com/maillist.html for more information. >> >> >> > >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with >the body of the message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. > > In practice, the FFT can be used to very easily obtain the integral or derivative of a time series (i.e. division or multiplication of all spectral points by i*frequency respectively). Since this is already built into Winquake, this would be the most efficient method, and is the one I always assumed was being used by Winquake. In this case there is no finite integration step, since the FFT is a sinusoidal fit, which is then played with.

Randall Pratt wrote:
Arie,

I don't have an answer but I have wondered about this also.  I've considered
summing as you thought and also the possibility of maybe trapazoidal areas
with several points.  Another question I have is how the result can begin at
other than zero displacement with a velocity sensor and zero time at file
start?  I wonder if the algorithym starts in the middle or from some average
point and works to the ends?

Randy

----- Original Message -----
From: "Arie Verveer" <ajbv@............>
To: <PSN-L@..............>
Sent: Tuesday, June 25, 2002 6:28 AM
Subject: Integration and Winquake


  
Hi, Just a small question;  When integrating data with Winquake
does anyone now the integration period.? I would assume the integrated
value is the sum of the y values times 1/ ( sample rate ) over the length
of the integration period? . I'm probably wrong, any idea's.


Cheers

Arie
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To leave this list email PSN-L-REQUEST@SEISMICNE
T.COM with
the body of the message (first line only): unsubscribe
See http://www.seismicnet.com/maillist.html
 for more information.

    

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Subject: Re: Mount Hood...
From: John Hernlund  hernlund@............ 
Date: Mon, 01 Jul 2002 16:29:27 -0700

It would be interesting to see if there has been any of the following 
trends:

- A shallowing of seismic activity over time, indicated upward migration 
of a magma body...
- Small topographic changes localized around the cone's immediate 
vicinity...
- Changes in gas flow and chemistry showing fresh movement and degassing...

 From what I have heard, none of these seems to be happening, but you 
never know with these things! There are some people using a remote 
sensing technique called InSAR which is a space-based radar 
interferogram of the ground which can detect very small changes in the 
shape of the ground. This type of thing has enormous potential for 
assessing volcanic risk since a change in shape over a broad region can 
be roughly inverted to find the depth of the magma expansion or 
disturbance using the theory of elasticity. Pretty cool stuff.

kArEEm wrote:

> What's everyone's guess about Mt. Hood in Oregon or have you been 
> following? There have been a remarkable number of quakes near the 
> cone. Yesterday morning's swarm started with a M4.8 bang and it was 
> followed by at least forty aftershocks.
>  
> Is she telling us something?
>  
> USGS Info 
>  
> Kareem





  
  


It would be interesting to see if there has been any of the following trends:



- A shallowing of seismic activity over time, indicated upward migration
of a magma body...

- Small topographic changes localized around the cone's immediate vicinity...

- Changes in gas flow and chemistry showing fresh movement and degassing...



From what I have heard, none of these seems to be happening, but you never
know with these things! There are some people using a remote sensing technique
called InSAR which is a space-based radar interferogram of the ground which
can detect very small changes in the shape of the ground. This type of thing
has enormous potential for assessing volcanic risk since a change in shape
over a broad region can be roughly inverted to find the depth of the magma
expansion or disturbance using the theory of elasticity. Pretty cool stuff.



kArEEm wrote:


  
  
  Message
   
  
 
  
 

 
  
 
  
What's
everyone's  guess about Mt. Hood in Oregon or have you been following? There
have been a  remarkable number of quakes near the cone. Yesterday morning's
swarm started  with a M4.8 bang and it was followed by at least forty aftershocks.
 

 
  
 

 
  
Is she telling  us something?
  

 
  
 

 
  
 
  
 

 
  
Kareem

  








Subject: Mount Hood Seismicity
From: DGentry509@.......
Date: Mon, 1 Jul 2002 21:21:40 EDT

 Click here: Mount Hood Seismicity This activity has a few reports that are 
deeper than the 1999 swarm. Like she's clearing her throat.

Don Gentry 
 Click here: Mount Hood Seismicity This activity has a few reports that are deeper than the 1999 swarm. Like she's clearing her throat.



Don Gentry 

Subject: Re: Mount Hood Seismicity
From:  earth@........... 
Date: Mon, 1 Jul 2002 20:14:04 -0700 (PDT)

 This activity has a few reports that
>  are 
> deeper than the 1999 swarm. Like she's clearing her throat.
> 
> Don Gentry 

Is it traditional to call all volcanos--shes'? I have often wondered...



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Public Seismic Network Mailing List (PSN-L)


Subject: Re: Mount Hood Seismicity
From:  earth@........... 
Date: Mon, 1 Jul 2002 20:13:33 -0700 (PDT)

 This activity has a few reports that
>  are 
> deeper than the 1999 swarm. Like she's clearing her throat.
> 
> Don Gentry 

Is it traditional to call all volcanos--shes'? I have often wondered...



__________________________________________________________

Public Seismic Network Mailing List (PSN-L)


Subject: Re: Mount Hood...
From: Bob Fryer  bfryer@............ 
Date: Tue, 2 Jul 2002 04:46:50 -0700

John,

I haven't heard of any such activities for Mt Hood; but last year (?) 
the discovery of a large bulge near South Sister (one of Three 
Sisters, Oregon Cascades volcanoes) caused quite a stir.

I do have a several dozen Mt Hood GIFs from Univ of Wash back to Jan. 
99 showing the various events shifting around, some near the 
fumaroles. Also have some lists if anyone wants them.

Bob Fryer

>It would be interesting to see if there has been any of the following trends:
>
>- A shallowing of seismic activity over time, indicated upward 
>migration of a magma body...
>- Small topographic changes localized around the cone's immediate vicinity...
>- Changes in gas flow and chemistry showing fresh movement and degassing...
>
>From what I have heard, none of these seems to be happening, but you 
>never know with these things! There are some people using a remote 
>sensing technique called InSAR which is a space-based radar 
>interferogram of the ground which can detect very small changes in 
>the shape of the ground. This type of thing has enormous potential 
>for assessing volcanic risk since a change in shape over a broad 
>region can be roughly inverted to find the depth of the magma 
>expansion or disturbance using the theory of elasticity. Pretty cool 
>stuff.
>
>kArEEm wrote:
>
>>Message
>>What's everyone's guess about Mt. Hood in Oregon or have you been 
>>following? There have been a remarkable number of quakes near the 
>>cone. Yesterday morning's swarm started with a M4.8 bang and it was 
>>followed by at least forty aftershocks.
>>
>>Is she telling us something?

-- 
    earthquake WARNING research
Animals, People, Scientific Evidence
    www.earthquakewarning.org
__________________________________________________________

Public Seismic Network Mailing List (PSN-L)


Subject: Filter
From: "Liberio Rossi"  liberossi@......... 
Date: Thu, 4 Jul 2002 06:06:05 +0200

Dear Larry,
Just to inform you that I am facing a problem:
When I push the button " F " in order to insert the filter,  the dialog =
box shows a label
where I read: You esecuted a wrong action. please, contact your =
supplier.

I am using winquake 2.8.9.

Can you help me.

Have my best regards
Liberio Rossi
liberossi@.........








Dear Larry,


Just to inform you that I am facing a=20
problem:


When I push the button " F " =
in=20
order to insert the filter,  the dialog box shows a =
label


where I read: You esecuted a wrong =
action. please,=20
contact your supplier.


 


I am using winquake 2.8.9.


 


Can you help me.


 


Have my best regards


Liberio Rossi


liberossi@.........
<=
/BODY>

Subject: Re: Filter
From: "Larry Cochrane"  cochrane@.............. 
Date: Wed, 3 Jul 2002 23:24:30 -0700

Hello Liberio,

What dialog box are you in when you press the "F" key? If you let me =
know the full title of the dialog box it will help me debug the problem.

Regards,
-Larry
  ----- Original Message -----=20
  From: Liberio Rossi=20
  To: psn-l@.................
  Sent: Wednesday, July 03, 2002 9:06 PM
  Subject: Filter


  Dear Larry,
  Just to inform you that I am facing a problem:
  When I push the button " F " in order to insert the filter,  the =
dialog box shows a label
  where I read: You esecuted a wrong action. please, contact your =
supplier.

  I am using winquake 2.8.9.

  Can you help me.

  Have my best regards
  Liberio Rossi
  liberossi@libero.it








Hello Liberio,


 


What dialog box are you in when you =
press the "F"=20
key? If you let me know the full title of the dialog box it will help me =
debug=20
the problem.


 


Regards,


-Larry



  
----- Original Message ----- 

  From:=20
  Liberio=20
  Rossi 
  
  
Sent: Wednesday, July 03, 2002 =
9:06=20
  PM

  
Subject: Filter

  


  
Dear Larry,

  
Just to inform you that I am facing a =

  problem:

  
When I push the button " F " =
in=20
  order to insert the filter,  the dialog box shows a =
label

  
where I read: You esecuted a wrong =
action.=20
  please, contact your supplier.

  
 

  
I am using winquake =
2.8.9.

  
 

  
Can you help me.

  
 

  
Have my best regards

  
Liberio Rossi

  
liberossi@.........
<=
/BLOCKQUOTE>

Subject: R: Filter
From: "Liberio Rossi"  liberossi@......... 
Date: Thu, 4 Jul 2002 09:11:33 +0200

Thanks Larry.
The F I sed appear in the bar placed over the box i said before together =
an "I"  and all commands to use for zumming etc.

it is enough to understanding what I means.
Thank Larry
Liberio Rossi
liberossi@.........

  ----- Original Message -----=20
  From: Larry Cochrane=20
  To: psn-l@.................
  Sent: Thursday, July 04, 2002 8:24 AM
  Subject: Re: Filter


  Hello Liberio,
  =20
  What dialog box are you in when you press the "F" key? If you let me =
know the full title of the dialog box it will help me debug the problem.
  =20
  Regards,
  -Larry
    ----- Original Message -----=20
    From: Liberio Rossi=20
    To: psn-l@.................
    Sent: Wednesday, July 03, 2002 9:06 PM
    Subject: Filter


    Dear Larry,
    Just to inform you that I am facing a problem:
    When I push the button " F " in order to insert the filter,  the =
dialog box shows a label
    where I read: You esecuted a wrong action. please, contact your =
supplier.

    I am using winquake 2.8.9.

    Can you help me.

    Have my best regards
    Liberio Rossi
    liberossi@.........








Thanks Larry.


The F I sed appear in the bar placed =
over the box i=20
said before together an "I"  and all commands to use for zumming=20
etc.


 


it is enough to understanding what I=20
means.


Thank Larry


Liberio Rossi


liberossi@.........


 



  
----- Original Message ----- 

  From:=20
  Larry=20
  Cochrane 
  
  
Sent: Thursday, July 04, 2002 =
8:24=20
  AM

  
Subject: Re: Filter

  


  
Hello Liberio,

  
 

  
What dialog box are you in when you =
press the "F"=20
  key? If you let me know the full title of the dialog box it will help =
me debug=20
  the problem.

  
 

  
Regards,

  
-Larry

  

    
----- Original Message ----- 

    From:=20
    Liberio=20
    Rossi 
    
To: psn-l@.............. 

    
Sent: Wednesday, July 03, =
2002 9:06=20
    PM

    
Subject: Filter

    


    
Dear Larry,

    
Just to inform you that I am facing =
a=20
    problem:

    
When I push the button " F =
"=20
    in order to insert the filter,  the dialog box shows a =

    label

    
where I read: You esecuted a wrong =
action.=20
    please, contact your supplier.

    
 

    
I am using winquake =
2.8.9.

    
 

    
Can you help me.

    
 

    
Have my best regards

    
Liberio Rossi

    
liberossi@.........
<=
/BLOCKQUOTE>


Subject: rFilter data
From: "Liberio Rossi"  liberossi@......... 
Date: Thu, 4 Jul 2002 11:19:34 +0200

Hi Larry,

The dialog box I mean is the one where we can see all the data =
concerning files.
On the first linewe can see " OPEN FILE"
File or files name                                             Directory

an empti space is ready to receive  all the file youreceived.
Under white space there are these buttons:

Open File      Add Event Report  Change Directory   Send e-mail message
Convert   Reply       UPdate      Delete       Help.

Well, Larry, over this dia Boxthere are these titles:

EVENT WINDOW - MENU and Tool Bar
On the tool bar there are the the following signs:

Diskette a button with eq over, the simbol of a map A PS button a button =
 with "loc"   "md"  "R/T  , " FFT"
another one button with " fft " (smaller characters)      " I "     " F =
",  one containin two pages , one handling 4 vertical bars, other two =
buttons and the button we press to see a MAP   Last one is "rst".

Larry, I beg you pardon for all the noise I given.
Hope now you will understand.
Have a good day and thanks for very appreciated help.
Liberio
liberossi@.........















Hi Larry,


 


The dialog box I mean is the one where =
we can see=20
all the data concerning files.


On the first linewe can see " OPEN=20
FILE"


File or files=20
name           &nb=
sp;           &nbs=
p;            =
;        =20
Directory


 


an empti space is ready to =
receive  all the=20
file youreceived.


Under white space there are these=20
buttons:


 


Open File      =
Add Event=20
Report  Change Directory   Send e-mail =
message


Convert  =20
Reply       =
UPdate     =20
Delete       Help.


 


Well, Larry, over this dia Boxthere are =
these=20
titles:


 


EVENT WINDOW - MENU and Tool =
Bar


On the tool bar there are the the =
following=20
signs:


 


Diskette a button with eq over, the =
simbol of a map=20
A PS button a button  with "loc"   "md"  "R/T  =
, "=20
FFT"


another one button with " fft " =
(smaller=20
characters)      " I "     =
" F=20
",  one containin two pages , one handling 4 vertical bars, other =
two=20
buttons and the button we press to see a MAP   Last one is=20
"rst".


 


Larry, I beg you pardon for all the =
noise I=20
given.


Hope now you will =
understand.


Have a good day and thanks for very =
appreciated=20
help.


Liberio


liberossi@.........


 


 


 


 


 


 


 


Subject: Mount Hood
From: John & Jan  johnjan@........ 
Date: Thu, 04 Jul 2002 07:07:46 -0600


>To:         Assistant Secretary for Water and Science
>             Chief of Staff
>             Director, Office of Communications
>
>From:       Barbara Wainman, Chief, Office of Communications, USGS
>
>Subject:    USGS Weekly Highlights, July 1-5, 2002
>
>I.  Departmental/Bureau News
>A.  Upcoming
>
>B. Current
>Record Earthquake at Mount Hood:  On June 29, the Mount Hood, Ore., area
>was shaken by a magnitude 4.5 earthquake located 3 miles below the south
>flank of the mountain.  As of July 2, there have been hundreds of
>aftershocks, including several felt events.  During the past 22 years of
>monitoring by the USGS and the Pacific Northwest Seismograph Network, the
>largest event detected prior to June 29 was M3.5.  At the present time, the
>events appear to be a typical mainshock/aftershock sequence of a tectonic
>earthquake.  Scientists have installed additional seismometers in the field
>and are watching events closely.  USGS will also monitor crustal movement
>and gas emissions.  (Willie Scott, Vancouver, WA, 360-993-8942)

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Subject: 24btis A/D converter 6 seismology
From: "Francois"  furansowa@........... 
Date: Thu, 4 Jul 2002 15:17:22 +0200

Hello dear all,

could someone explain me why you need 24bits AD converters in seismology.

Indeed it corresponds to 16.8millions points on a 2g scale, which thus
corresponds to a resolution of about 120 nano-g (10^-12g !)
Isn't the ambient noise muche higher than this ?

thanks in advance for "enlighting" me.

Francois

 
______________________________________________________________________________
ifrance.com, l'email gratuit le plus complet de l'Internet !
vos emails depuis un navigateur, en POP3, sur Minitel, sur le WAP...
http://www.ifrance.com/_reloc/email.emailif


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Subject: 24bits A/D converters & seismology
From: "Francois"  furansowa@........... 
Date: Thu, 4 Jul 2002 17:22:02 +0200

Hello dear all,

could someone explain me why you need 24bits AD converters in seismology.

Indeed it corresponds to 16.8millions points on a 2g scale, which thus
corresponds to a resolution of about 120 nano-g (10^-12g !)
Isn't the ambient noise much higher than this ?

thanks in advance for "enlighting" me.

Francois

 
______________________________________________________________________________
ifrance.com, l'email gratuit le plus complet de l'Internet !
vos emails depuis un navigateur, en POP3, sur Minitel, sur le WAP...
http://www.ifrance.com/_reloc/email.emailif


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Subject: Re: 24bits A/D converters & seismology
From: Jim Hannon  jmhannon@......... 
Date: Thu, 04 Jul 2002 11:43:30 -0500

Francios,
Most amateur systems work quite well with much less than 24 bits. In fact 
it is very difficult to build any electronics that will have noise low 
enough to work with 24 bits of resolution. Of course if you can it is nice 
to work with as much resolution as possible. It helps with not clipping on 
very large events or missing very small ones depending on how your system 
is adjusted. You don't have to adjust the gain of the system as carefully 
with more bits as you have more room for the signal to fit within the range 
of the A/D converter.

At 05:22 PM 7/4/02 +0200, you wrote:
>Hello dear all,
>
>could someone explain me why you need 24bits AD converters in seismology.
>
>Indeed it corresponds to 16.8millions points on a 2g scale, which thus
>corresponds to a resolution of about 120 nano-g (10^-12g !)
>Isn't the ambient noise much higher than this ?
>
>thanks in advance for "enlighting" me.
>
>Francois
>
>
>______________________________________________________________________________
>ifrance.com, l'email gratuit le plus complet de l'Internet !
>vos emails depuis un navigateur, en POP3, sur Minitel, sur le WAP...
>http://www.ifrance.com/_reloc/email.emailif
>

Jim Hannon
http://www.fmtcs.com/web/jmhannon
42,11.90N,91,39.26W
WB0TXL

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Public Seismic Network Mailing List (PSN-L)


Subject: Re: 24bits A/D converters & seismology
From: "Francois"  furansowa@........... 
Date: Thu, 4 Jul 2002 21:04:09 +0200

Hello Jim,
thank you for your answer!

Of course I understand that amateur systems do not need a 24bit A/D
converter : )

But I am wondering what is the reason why commercial seismometers have a
24bit A/D convertor.
How do you explain the need for such a hight sensitivity? (120 nano-g this
is so small!)
Don't you think that the seismic noise (assuming the eletronic noise is
reduced to minimum) is much bigger than hundrerds of nano-g ?
Do you think that commercial seismometers really use the full 24bit output
of there convertors? won't it be much enough to use 20bits (2 micro-g
resolution) ?

Francois

----- Original Message -----
From: "Jim Hannon" 
To: 
Sent: jeudi, 4. juillet 2002 18:43
Subject: Re: 24bits A/D converters & seismology


> Francios,
> Most amateur systems work quite well with much less than 24 bits. In fact
> it is very difficult to build any electronics that will have noise low
> enough to work with 24 bits of resolution. Of course if you can it is nice
> to work with as much resolution as possible. It helps with not clipping on
> very large events or missing very small ones depending on how your system
> is adjusted. You don't have to adjust the gain of the system as carefully
> with more bits as you have more room for the signal to fit within the
range
> of the A/D converter.
>
> At 05:22 PM 7/4/02 +0200, you wrote:
> >Hello dear all,
> >
> >could someone explain me why you need 24bits AD converters in seismology.
> >
> >Indeed it corresponds to 16.8millions points on a 2g scale, which thus
> >corresponds to a resolution of about 120 nano-g (10^-12g !)
> >Isn't the ambient noise much higher than this ?
> >
> >thanks in advance for "enlighting" me.
> >
> >Francois
> >
> >
>
>___________________________________________________________________________
___
> >ifrance.com, l'email gratuit le plus complet de l'Internet !
> >vos emails depuis un navigateur, en POP3, sur Minitel, sur le WAP...
> >http://www.ifrance.com/_reloc/email.emailif
> >
>
> Jim Hannon
> http://www.fmtcs.com/web/jmhannon
> 42,11.90N,91,39.26W
> WB0TXL
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
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> the body of the message (first line only): unsubscribe
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Subject: Re: 24bits A/D converters & seismology
From: westfall@.......
Date: Thu, 04 Jul 2002 14:43:34 -0700

Is it not the case that most commercial seismometers these days are
wideband instruments?  If so, they may need 24 bits to handle the
much larger dynamic range of these instruments.  Its possible that
20 bits might be enough, but vendors may have decided to go for the
extra 4 bits rather than restrict the range.  Considering the price
of a commercial instrument, the extra 4 bits probably does not add
to the cost of construction sufficiently to warrant changing the
price.  Its also possible that 24 bits (3 bytes) is preferred,
because it slightly simplifies the data processing software.
Comments?

Ron

----- Original Message -----
From: Francois 
Date: Thursday, July 4, 2002 12:04 pm
Subject: Re: 24bits A/D converters & seismology

> Hello Jim,
> thank you for your answer!
> 
> Of course I understand that amateur systems do not need a 24bit A/D
> converter : )
> 
> But I am wondering what is the reason why commercial seismometers 
> have a
> 24bit A/D convertor.
> How do you explain the need for such a hight sensitivity? (120 
> nano-g this
> is so small!)
> Don't you think that the seismic noise (assuming the eletronic 
> noise is
> reduced to minimum) is much bigger than hundrerds of nano-g ?
> Do you think that commercial seismometers really use the full 
> 24bit output
> of there convertors? won't it be much enough to use 20bits (2 
> micro-g
> resolution) ?

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Subject: Re: 24bits A/D converters & seismology
From: Hammonds  hammond@........... 
Date: Thu, 04 Jul 2002 13:52:15 -0800

Hi all,

This is from the ORFEUS 
website:  http://orfeus.knmi.nl/working.groups/wg1/standard.html

"The digitizer is a critical part in a VBB seismograph. It must however 
cover a dynamic range of at least 140 dB, and it must have
an excellent linearity and resolution because signals of greatly different 
amplitude may simultaneously be present in different
parts of the VBB seismic band."

So, the desire to have high dynamic range recording from broadband 
seismometers is in part why 24-bit digitizers are used.

Bob Hammond
Fairbanks, AK
http://apsn.awcable.com



At 01:43 PM 7/4/2002, you wrote:
>Is it not the case that most commercial seismometers these days are
>wideband instruments?  If so, they may need 24 bits to handle the
>much larger dynamic range of these instruments.  Its possible that
>20 bits might be enough, but vendors may have decided to go for the
>extra 4 bits rather than restrict the range.  Considering the price
>of a commercial instrument, the extra 4 bits probably does not add
>to the cost of construction sufficiently to warrant changing the
>price.  Its also possible that 24 bits (3 bytes) is preferred,
>because it slightly simplifies the data processing software.
>Comments?
>
>Ron
>
>----- Original Message -----
>From: Francois 
>Date: Thursday, July 4, 2002 12:04 pm
>Subject: Re: 24bits A/D converters & seismology
>
> > Hello Jim,
> > thank you for your answer!
> >
> > Of course I understand that amateur systems do not need a 24bit A/D
> > converter : )
> >
> > But I am wondering what is the reason why commercial seismometers
> > have a
> > 24bit A/D convertor.
> > How do you explain the need for such a hight sensitivity? (120
> > nano-g this
> > is so small!)
> > Don't you think that the seismic noise (assuming the eletronic
> > noise is
> > reduced to minimum) is much bigger than hundrerds of nano-g ?
> > Do you think that commercial seismometers really use the full
> > 24bit output
> > of there convertors? won't it be much enough to use 20bits (2
> > micro-g
> > resolution) ?
>
>__________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email PSN-L-REQUEST@.............. with
>the body of the message (first line only): unsubscribe
>See http://www.seismicnet.com/maillist.html for more information.

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Subject: Re: 24bits A/D converter 6 seismology
From: ChrisAtUpw@.......
Date: Thu, 4 Jul 2002 18:10:23 EDT

In a message dated 04/07/02, furansowa@........... writes:

> could someone explain me why you need 24bits AD converters in seismology.
> Indeed it corresponds to 16.8millions points on a 2g scale, which thus 
> corresponds to a resolution of about 120 nano-g (10^-12g !)
> 

Hi Francois,

       Some, but not all the '24 bit' A/Ds do give 24 bits if you take 
samples slowly enough. The range for 'normal' sampling rates may be 18 to 22 
bits. They will only effectively handle one channel / sensor at a time - the 
settling time on channel change tends to be rather long.
       The idea is that you don't then need amplifiers for your sensors and 
the one range will handle all possible signal levels, so you read a Geophone 
etc directly into the A/D. However, it may be more than a bit difficult to 
sense signals less than 100 nano Volts. I do not know what is done about the 
several micro volts of thermo-electric potentials that you will inevitably 
get, though.
       These and many other technical issues are described in detail in a 5.6 
MB file at http://www.ifjf.uib.no/seismo/SOFTWARE/OTHER/instrument.pdf
       This looks a very good 'book' and well worth keeping as a reference.

       Regards,

       Chris Chapman
In a message dated 04/07/02, furansowa@........... writes:



could 
someone explain me why you need 24bits AD converters in seismology.

Indeed it corresponds to 16.8millions points on a 2g scale, which thus corresponds to a resolution of about 120 nano-g (10^
-12g !)

Isn't the ambient noise much higher than this ?




Hi Francois,



       Some, but not all the '24 bit' A/Ds do give 24 bits if you take samples slowly enough.
 The range for 'normal' sampling rates may be 18 to 22 bits. They will only effectively handle one channel / sensor at a time -
 the settling time on channel change tends to be rather long.

       The idea is that you don't then need amplifiers for your sensors and the one range wil
l handle all possible signal levels, so you read a Geophone etc directly into the A/D. However, it may be more than a bit diffi
cult to sense signals less than 100 nano Volts. I do not know what is done about the several micro volts of thermo-electric pot
entials that you will inevitably get, though.

       These and many other technical issues are described in detail in a 5.6 MB file at http
://www.ifjf.uib.no/seismo/SOFTWARE/OTHER/instrument.pdf

       This looks a very good 'book' and well worth keeping as a reference.



       Regards,



       Chris Chapman

Subject: Re: 24bits A/D converters & seismology
From: Jim ODonnell  jimo17@........ 
Date: Thu, 4 Jul 2002 17:05:07 -0700

In a message dated 04/07/02, furansowa@........... writes: 


could someone explain me why you need 24bits AD converters in seismology.

Indeed it corresponds to 16.8millions points on a 2g scale, which thus
corresponds to a resolution of about 120 nano-g (10^-12g !) 
Isn't the ambient noise much higher than this ?
Hi Francois, 

Looks like you got our attention- Here is my shot at why!
Comments on why 24 bit digitizers are needed.
Even with 24 bit digitizers and 140 db BB seismometers, the seismographs
go off scale.  Look at the records for any large EQ M>7 and you will see
the seismographs go off scale if they are within a few hundred km. of the
epicenter; Taiwan and Hector Mine come to mind.  The solution is SM
seismographs which clip ~2g, I believe the largest acceleration recorded
are ~1.7 g from the Northridge M6.7 in 1994.  Note Larry Cochrane’s
PSN-accelerometer chip uses a Gain Ranging scheme to record High and Low
gain, utilizing the inexpensive 16 bit A/D, to stay on scale for the big
one (clips ~2g); but is still able to record some smaller events (clips
~70mg) which depends on the inherent noise of the chips, which are only
going to improve. 
See http://psn.quake.net/psnaccel/
 
 
Digitizer dynamic range ~1.0e07
10 bit=1024 or ~1.0 e03, 20 bit ~1.0 e06, and 24 bit ~16 e06  ~1.0e07 
 
Seismometer dynamic range for Good BB 1.0e07 (Best Guess for now)
140 db, 140/20 =7 orders of magnitude that is 1.0e07 
 
Earthquake amplitude  range: 1.0 e10
From M-1 to M8 we cover ~10 orders of amplitude velocity variation for
periods of 0.01 to 10 Hz. (See Chuck Ammon’s class notes from SLU for
plot on seismic ground amplitudes for earthquakes and comments, given
below:
http://www.eas.slu.edu/People/CJAmmon/HTML/Classes/IntroQuakes/Notes/seis
mometers.html
Seismic Signals
The range of ground motions that are interesting to seismologists is very
large because the process of earth deformation occurs at many different
rates and scales.
The amplitude range of interesting signals in earthquake studies as a
function of frequency compared with a similar range of physical
dimensions of some common items. Since I am comparing the "spectral"
amplitude as a function of frequency with physical dimensions of the
common items, the analogy is not perfect, but the range of variation in
size is well represented. "D" represents the distance from the
earthquake. We usually specify large distances over Earth's surface in
units of degrees and 1 degree = 111.19 km.

The large range of amplitudes we are interested in exists because we are
interested in all the processes occurring in Earth, from small rock
fractures that form in mines to the great earthquakes that occur each
year. The amount of energy released by these different processes is
enormous, and the large range of interesting amplitudes reflects this.
Jim O'Donnell/ UNLV 








In a message dated 04/07/02, furansowa@=
ifrance.com=20
writes: 


could someone explain me why you need 24bits AD converters in=
=20
  seismology. 
Indeed it corresponds to 16.8millions points on a 2g =
scale,=20
  which thus corresponds to a resolution of about 120 nano-g (10^-12g !)=20
  
Isn't the ambient noise much higher than this ?


Hi Francois, 



Looks like you got our =
attention- Here=20
is my shot at why!




Comments on why 24 bit =
digitizers are=20
needed.


Even with 24 bit digitizers and =
140 db BB=20
seismometers, the seismographs go off scale.  Look at the records for any large=
 EQ=20
M>7 and you will see the seismographs go off scale if they are within a =
few=20
hundred km. of the epicenter; Taiwan and Hector Mine come to mind.  The solution is SM seismographs =
which=20
clip ~2g, I believe the largest acceleration recorded are ~1.7 g from the=20
Northridge M6.7 in 1994.  =
Note Larry=20
Cochrane=92s PSN-accelerometer chip uses a Gain Ranging scheme to record =
High and=20
Low gain, utilizing the inexpensive 16 bit A/D, to stay on scale for the =
big one=20
(clips ~2g); but is still able to record some smaller events (clips ~70mg) =
which=20
depends on the inherent noise of the chips, which are only going to improve=
..=20



See http://psn.quake.net/psnaccel/<=
/P>

 


 


Digitizer dynamic =
range=20
~1.0e07


10 bit=3D1024 or ~1.0 e03, 20 =
bit ~1.0 e06,=20
and 24 bit ~16 e06  ~1.=
0e07=20



 


Seismometer dynamic range for =
Good BB=20
1.0e07 (Best Guess for now)


140 db, 140/20 =3D7 orders of =
magnitude=20
that is 1.0e07 


 


Earthquake amplitude  range: 1.0=20
e10


From M-1 to M8 we cover ~10 =
orders of=20
amplitude velocity variation for periods of 0.01 to 10 Hz. (See Chuck=
=20
Ammon=92s class notes from SLU for plot on seismic ground amplitudes for=
=20
earthquakes and comments, given below:


http://www.eas.slu.edu/People/CJAmmon/HTML/Classes=
/IntroQuakes/Notes/seismometers.html


Seismic Signals


The range of ground motions that are interesting to seismologists is =
very=20
large because the process of earth deformation occurs at many different =
rates=20
and scales.




      
The=
=20
      amplitude range of interesting signals in earthquake studies as a =
function=20
      of frequency compared with a similar range of physical dimensions of =
some=20
      common items. Since I am comparing the "spectral" amplitude as a =
function=20
      of frequency with physical dimensions of the common items, the =
analogy is=20
      not perfect, but the range of variation in size is well=20
      represented. "D" represents the distance from the earthquake. We =
usually=20
      specify large distances over Earth's surface in units of degrees and =
1=20
      degree =3D 111.19 km.

  
  

    


The large range of amplitudes we are interested in exists because we are=
=20
interested in all the processes occurring in Earth, from small rock =
fractures=20
that form in mines to the great earthquakes that occur each year. The =
amount of=20
energy released by these different processes is enormous, and the large =
range of=20
interesting amplitudes reflects this.


Jim O'Donnell/ UNLV 


Subject: =?iso-8859-1?Q?Water_rocket?=
From: "=?iso-8859-1?Q?jean-pierre-laine@..............  jean-pierre-laine@laposte.net 
Date: Fri,  5 Jul 2002 12:42:32 +0200

hello
go to 
perso.wanadoo.fr/fusee
bye

Acc=E9dez au courrier =E9lectronique de La Poste : www.laposte.net ; 3615 LAPOSTENET (0,13 =80/mn) ; t=E9l : 08 92 68 13 50 (0,
34=80/mn)"



__________________________________________________________

Public Seismic Network Mailing List (PSN-L)


Subject: =?iso-8859-1?Q?Water_rocket?=
From: "=?iso-8859-1?Q?jean-pierre-laine@..............  jean-pierre-laine@laposte.net 
Date: Fri,  5 Jul 2002 12:42:32 +0200

hello
go to 
perso.wanadoo.fr/fusee
bye

Acc=E9dez au courrier =E9lectronique de La Poste : www.laposte.net ; 3615 LAPOSTENET (0,13 =80/mn) ; t=E9l : 08 92 68 13 50 (0,
34=80/mn)"



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Subject: Lehman construction question
From: "Jim Martin"  jimdmartin@................ 
Date: Sun, 7 Jul 2002 16:30:14 -0500

I am a new member to this list, and am also building my first Lehman seis.
I have a couple of questions:

1).  I am using a 1/2" steel threaded rod for the boom.  Will this be ok,
or should the boom be of non-ferrous material?

2).  Is there a recommended distance between the boom pivot point and the
boom support wire attachment point?

I know that initially the boom wire pivot should lead the boom pivot by
about 1cm,  but I am just curious if there is a recommended max distance
from boom to upper crossarm.

Thanks to everyone....

Jim D. Martin
Fort Wayne, Indiana



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Public Seismic Network Mailing List (PSN-L)


Subject: Re: 24bits A/D converters & seismology
From: "Barry"  gbl@....... 
Date: Mon, 8 Jul 2002 20:16:22 -0700

Hi Jim et al
      I like the auto-variable gain idea. I have in the past run a 12 =
bit A/D with a variable gain (1- 1024). The triggering routine and how =
you store the data gets a little complicated, but it works pretty well. =
There can be a slight zero shift when the computer changes gains. I used =
a Maxim 16 position switch with a resistor ladder. It's best run running =
at a reasonable gain and if an event occurs, then the gain is reduced by =
multiples of two to stay on scale. One can store the gain setting for =
each data point at the lower bit area. 16 bit with variable gain is what =
I'm shooting for. =20
Regards
Barry










Hi Jim et al


      I like =
the=20
auto-variable gain idea. I have in the past run a 12 bit A/D with a =
variable=20
gain (1- 1024). The triggering routine and how you store the data gets a =
little=20
complicated, but it works pretty well. There can be a slight zero shift =
when the=20
computer changes gains. I used a Maxim 16 position switch with a =
resistor=20
ladder. It's best run running at a reasonable gain and if an event =
occurs, then=20
the gain is reduced by multiples of two to stay on scale. One can =
store the=20
gain setting for each data point at the lower bit area. 16 bit with =

variable gain is what I'm shooting for.  


Regards


Barry


 



  
 


Subject: Lowpass Band Filter
From: "Euro Atencio"  eatencio@.......... 
Date: Mon, 15 Jul 2002 17:24:19 -0500

Hi Larry or anyone with Larry's Filter board!!

I don't know why I'm not having any lowpass band filter.

Hope I could hear suggestions;

Euro










Hi Larry or anyone with Larry's Filter=20
board!!


 


I don't know why I'm not having any =
lowpass band=20
filter.


 


Hope I could hear =
suggestions;


 


Euro


Subject: LEHMAN
From: "Euro Atencio"  eatencio@.......... 
Date: Tue, 16 Jul 2002 06:17:05 -0500

I am localized in Orlando, Florida and I built a Lehman that it  is seam =
to be that my sensor has a resonance of ~8 to 10 Hz, so the lowpass band =
filter can not work properly; if there is someone near by or could help =
me with this please let me know.

Best Regards;

Euro








I am localized in Orlando, Florida and =
I built=20
a Lehman that it  is seam to be that my sensor has a resonance =
of ~8=20
to 10 Hz, so the lowpass band filter can not work properly; if =
there is=20
someone near by or could help me with this please let me =
know.


 


Best Regards;


 


Euro


Subject: FW: [EDIS]  EQ 3 14 SANTA CLARA COUNTY [News: San Francisco Bay]
From: jim_oberhofer@...........
Date: Wed, 17 Jul 2002 14:57:22 -0600

FYI... 

Jim O, Cupertino, CA

-----Original Message-----
From: EDIS Email Service [mailto:edismail@.............
Sent: Wednesday, July 17, 2002 12:32 PM
To: EDIS-by-Email@............
Subject: [EDIS] EQ 3 14 SANTA CLARA COUNTY [News: San Francisco Bay]


PRELIMINARY EARTHQUAKE REPORT
Rapid Earthquake Location Service
U.S. Geological Survey, Menlo Park, California
U.C. Berkeley Seismological Laboratory, Berkeley, California

Version 2: Updates lower and earlier versions of this earthquake report

A MINOR EARTHQUAKE OCCURRED AT 12:07 PM PDT Wednesday, Jul 17, 2002.
THE MAGNITUDE 3.1 (ML) EVENT IS LOCATED  11 MILES N   OF MORGAN HILL, CA
THE HYPOCENTRAL DEPTH IS   4.0 MILES.

This event has been reviewed by the USGS on-duty seismologist.

PRINCIPAL EARTHQUAKE PARAMETERS
_______________________________

Magnitude              : 3.14  ML
Event Date & Time      : 07/17/2002   12:07:42 PM PDT
07/17/2002   19:07:42    UTC
Location               : 37.2897 N, 121.6658 W
            : (37 deg. 17.38 min. N, 121 deg. 39.95 min. W)
Depth                  :    6.5 km. deep (   4.0 miles)
Location Quality       : Excellent

18 km ( 11 miles) N   (356 degrees) of Morgan Hill, CA
21 km ( 13 miles) ESE (105 degrees) of San Jose City Hall, CA
23 km ( 14 miles) NNW (347 degrees) of San Martin, CA
25 km ( 16 miles) E   ( 89 degrees) of Campbell, CA
26 km ( 16 miles) SE  (126 degrees) of Milpitas, CA

ADDITIONAL EARTHQUAKE PARAMETERS
________________________________

number of phases             : 149
rms misfit                   :   0.07 seconds
horizontal location error    :   0.1  km
vertical location error      :   0.3  km
maximum azimuthal gap        :  50    degrees
distance to nearest station  :   3.   km
event ID:   51120424


EDIS-07-17-02 1223 PDT


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Subject: FS: ISA A/D board
From: Greg  geo@........... 
Date: Thu, 18 Jul 2002 13:21:56 -0700

I got permission to post this.

I'm entertaining offers on my ISA A/D board. It has the 16 bit 
Burr-Brown chip on it. Larry made it. I can put a picture on a 
webserver, but it's just like the pics on Larry's site. 
http://psn.quake.net/atod.html
It looks like the Rev 2 board.

I have the WWV circuit, but not the thermally isolated timer 
what-cha-ma-jigger (goes in the big open space on the end of the board). 
It's still $245 new? I have a "D" shell connector (2 wires soldered) and 
floppies (SDR and 32 bit Winquake) for it also. Oh yeah, it works fine.

You might want to check to see if you have an open ISA slot and a free 
IRQ before you decide you want it. If you really want, I can sell you a 
computer to go along with it. I have a spare P133 system that I can 
install it in. It has 64 MB EDO RAM, NE2000 network card, CDROM and a 
2.5 GB hard drive. A MSDOS license is up to you to get. No monitor. 
Shipping will probably be pricey though.

I took it out of the computer and disconnected everything. Send offers 
straight to me. Not to the list. I can give you my ebay account name if 
you want to look at my feedback. It's 16 positive, 0 neutral and 0 negative.

Thanks,
Greg

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Subject: AS-1 Seismograph for sale
From: "angel@.........  angel@chiriqui.com 
Date: Sat, 20 Jul 2002 19:42:20 -0500

Hello Everyone,

I have an AS-1 Seismograph for sale for $275.00  I paid $425.. This is
complete turnkey system.  It includes everything, power supply,
electronics and seismograph.  Just plug it and ready to go.  Uses
Amaseis software. (Also the AS-1 software)

http://www.eas.purdue.edu/~braile/edumod/as1mag/as1mag.htm

I can take PayPal


Best regards,
 angel                          mailto:angel@..............

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Subject: New WinSDR release
From: "Larry Cochrane"  cochrane@.............. 
Date: Sat, 27 Jul 2002 16:13:20 -0700

All,

I have a new WinSDR release available on my web site. You can download it
from here http://www.seismicnet.com/winsdr/. The release version number is
2.0.7. There are two new features in WinSDR. The first one is the ability to
filter the data used to produce the GIF images. In the GIF Settings dialog
box you will see a new group box called Filter Control. You can enable or
display lowpass and highpass filters, set the cutoff frequency and the
number of poles for each channel using the controls in this group box.

A note about digital filtering. The process of digital filtering can take a
lot of CPU time to filter the data used to produce the GIF images. You need
to make sure your system is fast enough to had the extra load on the system
when you filter the GIF images. One way of monitoring how well your system
is running, is to open the Status Viewer (use the View / Status Viewer menu
items to open this dialog box) in WinSDR and keep an eye on the Max Input
Queue number on the bottom right hand side of the dialog box. The first
number is the maximum number of RS-232 input characters seen in the input
queue. The second number is the size of the queue. This is currently set to
32678. If the system is very busy doing other things, like creating GIF
images, then reading the input data, the input max input queue number will
get larger. If WinSDR cannot keep up with the data coming from the A/D
board, the input queue will fill up to 32768 and you will start seeing data
errors do to the loss of data. If this happens, you either need to turn off
filtering or get a faster system.


The other thing new with WinSDR is the support for a new GPS receiver. I was
looking around for other GPS options other then the Motorola ONCORE receiver
and came across the Garmin GPS 16 Sensor. This receiver has the antenna
built in and it has the all important 1 pulse per second output signal
needed for accurate time keeping. More info on the receiver can be found
here http://www.garmin.com/products/gps16/index.html. This is a very nice
receiver. Since the receiver and antenna are mounted together, extending the
data cable length between your datalogger system and the receiver can be
done with a standard 9-pin to 9-pin RS-232 cable. I have tried 50 feet (~16
me) of cable without any problems. The receivers I have been getting run on
~5 VDC, higher voltage models are also available. What I have been doing is
adding two jumpers on my serial output A/D board that supply +5 volts to the
receiver and a ground signal through the RS-232 cable. Since the receiver
inputs/outputs standard RS-232 signal levels (except the 1 PPS signal, it's
0 to 5 v) there is no need for a interface board like what's needed for the
ONCORE receiver.

To use this new GPS receiver you must upgrade your A/D board firmware to
version 2.0. The new firmware version is included in the install package. In
the System Settings dialog box in WinSDR you will see a new Time Reference
Type called GPS Garmin. If you are using the Oncore receiver, make sure you
select the GPS ONCORE item. An adapter is needed to covert the RJ45 8 pin
connector to a 9-pin RS-232 connector. I have information on this page on
how to do this http://www.seismicnet.com/winsdr/gps.html.

The Garmin GPS 16 also supports a new differential GPS system called WAAS.
Currently it's only available here in the States. More info on WAAS can be
found on the Garmin site. If the receiver can see one of the two WAAS
geostationary satellites, the position information can be improved to less
the 5 meters. The WAAS signal is not needed for accurate time keeping.

That's it....

Larry Cochrane
Redwood City, PSN


__________________________________________________________

Public Seismic Network Mailing List (PSN-L)


Subject: Economical High Quality Magnets
From: "Connie and Jim Lehman"  lehmancj@........... 
Date: Fri, 2 Aug 2002 10:05:32 -0400

It was brought to my attention recently a good source of magnets for =
coil pickup or damping purposes are to be found in discarded microwave =
units.  It takes a bit of digging, but within the klystron or similar =
box within, in most models there is a pair of strong cylindrical magnets =
for the taking.
                                                 Good digging,  J. =
Lehman,  Harrisonburg, VA.








It was brought to my =
attention recently=20
a good source of magnets for coil pickup or damping purposes are to be =
found in=20
discarded microwave units.  It takes a bit of digging, but within =
the=20
klystron or similar box within, in most models there is a pair of strong =

cylindrical magnets for the taking.


          &nbs=
p;            =
;            =
            &=
nbsp;=20
Good digging,  J. Lehman,  Harrisonburg,=20
VA.


Subject: Re: Economical High Quality Magnets
From: ChrisAtUpw@.......
Date: Fri, 2 Aug 2002 17:45:48 EDT

In a message dated 02/08/02, lehmancj@........... writes:

> It was brought to my attention recently a good source of magnets for coil 
> pickup or damping purposes are to be found in discarded microwave units.  

       These magnetron magnets are fine for coil pickups, but the field is a 
bit low and the gap rather too wide for efficient damping.
       For damping magnets, I suggest going to Forcefield at 
http://www.wondermagnet.com/dev/magnets.html and getting a pair of #21's at 
$4.20 each. Type #39 at $12.50 each are even stronger. A sheet of 1/8" copper 
in the gap feels like it is moving in thick treacle!

       Type #41 at $1.75 and pairs of Types # 2 at $2.00, or #42 at $2.50 
mounted on mild steel backing plates will give very good signals from coils 
of ~1" dia. These magnets have a N and a S pole on each 'wing' of the face 
and a coil should be mounted centrally over the face. 

       Regards,

       Chris Chapman
In a message dated 02/08/02, lehmancj@........... writes:



It was
 brought to my attention recently a good source of magnets for coil pickup or damping purposes are to be found in discarded mic
rowave units.  




       These magnetron magnets are fine for coil pickups, but the field is a bit low and the 
gap rather too wide for efficient damping.

       For damping magnets, I suggest going to Forcefield at http://www.wondermagnet.com/dev/
magnets.html and getting a pair of #21's at $4.20 each. Type #39 at $12.50 each are even stronger. A sheet of 1/8" copper in th
e gap feels like it is moving in thick treacle!



       Type #41 at $1.75 and pairs of Types # 2 at $2.00, or #42 at $2.50 mounted on mild ste
el backing plates will give very good signals from coils of ~1" dia. These magnets have a N and a S pole on each 'wing' of the 
face and a coil should be mounted centrally over the face. 



       Regards,



       Chris Chapman

Subject: Re: Economical High Quality Magnets
From: CapAAVSO@.......
Date: Sat, 3 Aug 2002 08:58:10 EDT

In a message dated 8/2/02 10:46:13 PM GMT Daylight Time, ChrisAtUpw@....... 
writes:


> For damping magnets, I suggest going to Forcefield at 
> http://www.wondermagnet.com/dev/magnets.html and getting a pair of #21's at 
> $4.20 each. Type #39 at $12.50 each are even stronger. A sheet of 1/8" 
> copper in the gap feels like it is moving in thick treacle! 

Hi Chris,

The best I can find is 1/32 thick copper sheet and as a damping magnet it 
moves more like it is in very watered down treacle. If I stacked four of 
these would I get the same damping effect as if I used a 1/8 thick plate?

Cap
(Casper Hossfield)
In a message dated 8/2/02 10:46:13 PM GMT Daylight Time, ChrisAtUpw@....... writes:






For dampin
g magnets, I suggest going to Forcefield at http://www.wondermagnet.com/dev/magnets.html and getting a pair of #21's at $4.20 e
ach. Type #39 at $12.50 each are even stronger. A sheet of 1/8" copper in the gap feels like it is moving in thick treacle! 




Hi Chris,



The best I can find is 1/32 thick copper sheet and as a damping magnet it moves more like it is in very watered down treacle. I
f I stacked four of these would I get the same damping effect as if I used a 1/8 thick plate?



Cap

(Casper Hossfield)

Subject: Re: Economical High Quality Magnets
From: ChrisAtUpw@.......
Date: Sat, 3 Aug 2002 17:13:30 EDT

In a message dated 03/08/02, CapAAVSO@....... writes:

> Hi Chris,
> The best I can find is 1/32 thick copper sheet and as a damping magnet it 
> moves more like it is in very watered down treacle. If I stacked four of 
> 

Hi Cap,

       I made a typing error. For #21 please read #31. Sorry about that. The 
price quoted was correct.

       It would probably not be quite as good, but it could be adequate. Thin 
sheet Cu is likely to be harder. One important thing to remember is that the 
Copper needs to extend an appreciable distance beyond the end of the high 
field change region of the magnets. (Prefereably to between 1.5x or 2x the 
magnet width) I have a couple of #31s which are separated by 4 mm and the 
magnets themselves are about 17 mm wide. The magnet pairs are fixed on 5 mm 
thick iron  backing plates (as supplied). The maximum damping is for 
movements parallel to the long axis of the magnets.  The Copper needs to 
extend at least 10 mm on each side of the central magnet junction, making the 
plate over 40 mm wide and extending above and below the magnets themselves. 
My damping plate is a stubby T shape, 50 mm high and about 38 mm wide across 
the column of the T. The free damping movement is about +/- 2.5 mm. 
       You can feel the difference if you slide the magnet pair up and down 
the edge of a Cu sheet and compare this drag with that which you get when you 
put the corner of the sheet through the centre of the gap.  
       Hope that this will help,

       Regards,

       Chris Chapman
In a message dated 03/08/02, CapAAVSO@....... writes:



Hi Chr
is,

The best I can find is 1/32 thick copper sheet and as a damping magnet it moves more like it is in very watered down treacl
e. If I stacked four of these would I get the same damping effect as if I used a 1/8 thick plate?




Hi Cap,



       I made a typing error. For #21 please read #31. Sorry about that. The price quoted was
 correct.



       It would probably not be quite as good, but it could be adequate. Thin sheet Cu is lik
ely to be harder. One important thing to remember is that the Copper needs to extend an appreciable distance beyond the end 
of the high field change region of the magnets. (Prefereably to between 1.5x or 2x the magnet width) I have a couple of #31
s which are separated by 4 mm and the magnets themselves are about 17 mm wide. The magnet pairs are fixed on 5 mm thick iron &n
bsp;backing plates (as supplied). The maximum damping is for movements parallel to the long axis of the magnets.  The Copp
er needs to extend at least 10 mm on each side of the central magnet junction, making the plate over 40 mm wide and extending a
bove and below the magnets themselves. My damping plate is a stubby T shape, 50 mm high and about 38 mm wide across the column 
of the T. The free damping movement is about +/- 2.5 mm. 

       You can feel the difference if you slide the magnet pair up and down the edge of a Cu 
sheet and compare this drag with that which you get when you put the corner of the sheet through the centre of the gap.  

       Hope that this will help,



       Regards,



       Chris Chapman

Subject: shaking in Panama
From: "angel@.........  angel@chiriqui.com 
Date: Tue, 6 Aug 2002 07:13:58 -0500

Hello,

Here is a summary of the shaking in Panama.

http://www.volcanbaru.com/news.html



angel

__________________________________________________________

Public Seismic Network Mailing List (PSN-L)


Subject: Re: Economical High Quality Magnets
From: "Larry Cochrane"  cochrane@.............. 
Date: Tue, 6 Aug 2002 16:38:42 -0700

Greetings,

If you are wondering if J. Lehman has anything to do with the Lehman =
sensor he, Jim or James Lehman, is the designer of the Lehman sensor =
that was described in the 1979 The Amateur Scientist section of the =
Scientific American magazine. If you have not read the article I have it =
online here: http://www.seismicnet.com/lehmntxt.html

-Larry Cochrane
Redwood City, PSN
  ----- Original Message -----=20
  From: Connie and Jim Lehman=20
  To: psn-l@.................
  Sent: Friday, August 02, 2002 7:05 AM
  Subject: Economical High Quality Magnets


  It was brought to my attention recently a good source of magnets for =
coil pickup or damping purposes are to be found in discarded microwave =
units.  It takes a bit of digging, but within the klystron or similar =
box within, in most models there is a pair of strong cylindrical magnets =
for the taking.
                                                   Good digging,  J. =
Lehman,  Harrisonburg, VA.








Greetings,


 


If you are wondering if J. Lehman has =
anything to=20
do with the Lehman sensor he, Jim or James Lehman, is the designer of =
the Lehman=20
sensor that was described in the 1979 The Amateur Scientist section =
of=20
the Scientific American magazine. If you have not read the article =
I have=20
it online here: http://www.seismicnet.co=
m/lehmntxt.html


 


-Larry Cochrane


Redwood City, PSN



  
----- Original Message ----- 

  From:=20
  Connie and=20
  Jim Lehman 
  
  
Sent: Friday, August 02, 2002 =
7:05=20
  AM

  
Subject: Economical High =
Quality=20
  Magnets

  


  
It was brought to my =
attention=20
  recently a good source of magnets for coil pickup or damping purposes =
are to=20
  be found in discarded microwave units.  It takes a bit of =
digging, but=20
  within the klystron or similar box within, in most models there is a =
pair of=20
  strong cylindrical magnets for the taking.

  
          &nbs=
p;            =
;            =
            &=
nbsp;=20
  Good digging,  J. Lehman,  Harrisonburg,=20
VA.


Subject: Outage using PSN.QUAKE.NET
From: "Larry Cochrane"  cochrane@.............. 
Date: Tue, 6 Aug 2002 19:13:36 -0700

All,

Some of you may have experienced problems accessing my web site starting
sometime over the weekend. I took a long needed vacation, my first ship
cruise to Ensenada Mexico. I had a great time. While I was gone my backup
DSL line went down. If you tried to access a URL ending in PSN.QUAKE.NET you
would get a timeout error. The problem occurred because the psn.quake.net
domain name resolves back to the backup DSL line and I have no control over
the domain name to IP address mapping. My first ISP was Quake.Net so they
added the PSN part to their domain name server. As far as I know Quake.Net
is now out of business, just like a lot of the other small ISP that started
up when the Internet got popular.

Since this domain name could go way at any time you should change any
Bookmarks or Favorites using psn.quake.net to www.seismicnet.com. Also, if
you have any web pages that have the old domain name you should change it to
the seismicnet.com name. Since I run my own DNS server for seismicnet.com,
seismicnet.org and webtronics.com I have compete control over these domain
names.

Regards,
Larry Cochrane
Redwood City, PSN


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Public Seismic Network Mailing List (PSN-L)


Subject: M13 quake?
From: "David Saum"  DSaum@............ 
Date: Thu, 8 Aug 2002 13:52:11 -0400

Science News has an article this
Week of Aug. 3, 2002; Vol. 162, No. 5

that says the imact that wiped out the dinosaurs
caused at M13 quake.  Registered subscribers
can read the article online.

References here:
http://www.sciencenews.org/20020803/fob2ref.asp

West Coast Shimmy: Smack from space triggered landslides along Pacific Coast

Scientists say they've found the first evidence along the Pacific Coast of
massive landslides triggered by the impact from space 65 million years ago
that's suspected to have wiped out the dinosaurs


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Public Seismic Network Mailing List (PSN-L)


Subject: FFT
From: "Rolando Benitez"  rbenitez@........ 
Date: Thu, 8 Aug 2002 21:56:59 -0600

Larry et al,
I am a newcomer -almost- in this list and an apprentice of the earthquakes
sciences, I have been posting events at the PSN web page since late May,
having the good fortune to live in the middle of a very active area, I have
posted a few. As a beginner I need to learn a lot about many things, I have
received wonderful help from several PSN members, thank to them I am
enjoying this very much. I would like to address some questions to the group
looking for some light in the area of what the FFT module of WINQUAKE is,
I've used the filters in a very practical and blind way, so I have a slight
idea of what it can be used for,  but have no clue in the relationship among
the period of sensor and the freq of the event and the proximity of quake,
etc, and the FFT screen, so I really need further assistance. Can someone
give me some light, please? How can I find some info in the Internet, book,
etc.,? Your help would be very appreciated.
Best regards from Fraijanes, Guatemala.
Rolando Benitez

__________________________________________________________

Public Seismic Network Mailing List (PSN-L)


Subject: Re: FFT
From: "Larry Cochrane"  cochrane@.............. 
Date: Sat, 10 Aug 2002 12:54:55 -0700

Rolando,

I'm far from an expert on FFTs. You should be able to fine more information
on the Internet if you do a search on Fast Fourier Transform. Many years ago
I found some code on the Net that does the FFT. I basically treat the FFT
function as a block box. How it works involves a lot of math that's above my
head.... What's amazing is it only takes a few lines of "C" code to do the
FFT function.

To filter the data in WinQuake you should use the Time Domain filtering
rather then using the filtering in the FFT Window. The time domain filtering
produces less errors or distortion then using the FFT filtering. The reason
is errors are introduced when you do the FFT and again when you do the
inverse FFT to get the data back into the time domain.

The reason for the filtering is to remove unwanted noise in the data. As an
example if you record a teleseismic event there is no need for data above
one or two Hertz.  Since the local man made (or is it person made in these
PC times?) noise is usually above one or two Hertz one can do a lowpass
filter to remove the local ground noise.

Hope this helps.

-Larry Cochrane
Redwood City, PSN

----- Original Message -----
From: "Rolando Benitez" 
To: "Psn-L@........... Com" 
Sent: Thursday, August 08, 2002 8:56 PM
Subject: FFT


> Larry et al,
> I am a newcomer -almost- in this list and an apprentice of the earthquakes
> sciences, I have been posting events at the PSN web page since late May,
> having the good fortune to live in the middle of a very active area, I
have
> posted a few. As a beginner I need to learn a lot about many things, I
have
> received wonderful help from several PSN members, thank to them I am
> enjoying this very much. I would like to address some questions to the
group
> looking for some light in the area of what the FFT module of WINQUAKE is,
> I've used the filters in a very practical and blind way, so I have a
slight
> idea of what it can be used for,  but have no clue in the relationship
among
> the period of sensor and the freq of the event and the proximity of quake,
> etc, and the FFT screen, so I really need further assistance. Can someone
> give me some light, please? How can I find some info in the Internet,
book,
> etc.,? Your help would be very appreciated.
> Best regards from Fraijanes, Guatemala.
> Rolando Benitez
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>


__________________________________________________________

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Subject: Re: FFT
From: "Randall Pratt"  randallpratts@.......... 
Date: Thu, 10 Aug 2000 19:56:50 -0500

Hi All,

I found this site last spring.  It has some good FFT explanation.
http://www.dspguide.com/pdfbook.htm

Randy

----- Original Message -----
From: "Rolando Benitez" 
To: "Psn-L@........... Com" 
Sent: Thursday, August 08, 2002 10:56 PM
Subject: FFT


> Larry et al,
> I am a newcomer -almost- in this list and an apprentice of the earthquakes
> sciences, I have been posting events at the PSN web page since late May,
> having the good fortune to live in the middle of a very active area, I
have
> posted a few. As a beginner I need to learn a lot about many things, I
have
> received wonderful help from several PSN members, thank to them I am
> enjoying this very much. I would like to address some questions to the
group
> looking for some light in the area of what the FFT module of WINQUAKE is,
> I've used the filters in a very practical and blind way, so I have a
slight
> idea of what it can be used for,  but have no clue in the relationship
among
> the period of sensor and the freq of the event and the proximity of quake,
> etc, and the FFT screen, so I really need further assistance. Can someone
> give me some light, please? How can I find some info in the Internet,
book,
> etc.,? Your help would be very appreciated.
> Best regards from Fraijanes, Guatemala.
> Rolando Benitez
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.

__________________________________________________________

Public Seismic Network Mailing List (PSN-L)


Subject: Re: FFT
From: "Barry"  gbl@....... 
Date: Sun, 11 Aug 2002 07:25:03 -0700

Rolando
    I'll contribute a little. As I understand it, any signal can be
representated by a sum of sine waves of different frequencies and
magnitudes. With the FFT, the math routine has selected multiples of 2 to
speed up the calculation process. You  don't get as much of the frequency
spectrum but it calculates faster. What you  see when you run an FFT is the
magnitude sum of the various sign waves ploted as a function of frequency
for that given quake and your sensor.  I, as an example,  usually filter
teleseismic events to remove frequencies below 0.003 hz and above 0.5 to 1
hz ( so my files won't be so large.) . You should save events at a sampling
frequency twice the value of the highest frequency  of interest (Nuquest ).
I think what happens if you save higher frequencies than the sampling rate,
the sampling picks  points on different signal cycles (like a beat) and a
higher frequency can look like a low one in the FFT.
Regards
Barry

> > Larry et al,
> > I am a newcomer -almost- in this list and an apprentice of the
earthquakes
> > sciences, I have been posting events at the PSN web page since late May,
> > having the good fortune to live in the middle of a very active area, I
> have
> > posted a few. As a beginner I need to learn a lot about many things, I
> have
> > received wonderful help from several PSN members, thank to them I am
> > enjoying this very much. I would like to address some questions to the
> group
> > looking for some light in the area of what the FFT module of WINQUAKE
is,
> > I've used the filters in a very practical and blind way, so I have a
> slight
> > idea of what it can be used for,  but have no clue in the relationship
> among
> > the period of sensor and the freq of the event and the proximity of
quake,
> > etc, and the FFT screen, so I really need further assistance. Can
someone
> > give me some light, please? How can I find some info in the Internet,
> book,
> > etc.,? Your help would be very appreciated.
> > Best regards from Fraijanes, Guatemala.
> > Rolando Benitez
> >
> > __________________________________________________________
> >
> > Public Seismic Network Mailing List (PSN-L)
> >
> > To leave this list email PSN-L-REQUEST@.............. with
> > the body of the message (first line only): unsubscribe
> > See http://www.seismicnet.com/maillist.html for more information.
> >
>
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
>


__________________________________________________________

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Subject: Re: FFT
From: "Randall Pratt"  randallpratts@.......... 
Date: Fri, 11 Aug 2000 14:22:09 -0500

I have a good example of Nyquist frequency behavior in an FFT.
I used EMON and substitued the collect routine with a function
y=250*sin(m*data point number).  In other words, each point was on a pure
sine wave and in sync with the sample rate.  At the rate of 8.46 samples/sec
this resulted in a basic sine wave period of 42.5532 seconds.  I then slowed
the sample rate by averaging 6 samples per point giving a sample rate of
1.41sps but the wave period remained the same with m=1.  Next I incremented
m to 20, 40, 60, 80 to effectively increase the frequency by those
multiples.  I have posted the data file nyquist.fft at
http://www.santel.net/~randallpratts/ if you want to play with it.  Starting
with m=20 or 20* the basic frequency we would expect the period to be
2.1277sec and we measure 2.131 from FFT.  Here we would have 3 data points
per cycle.  The next frequencies are above Nyquist and have fewer than 2
data points in a complete sine wave.  The expected frequency goes up and the
FFT measured frequency goes down.  Notice how both 20 times and 60 times the
basic frequency look the same on the FFT.  Once the high frequency is
aliased in I don't know how it could be filtered out.  Someone else may
answere that.

rn Measured period freq ratio theory ratio expected period meas/exp
points/cycle
20         2.145         1.0000         20.00         2.1277
1.01             3.00
40         1.429         1.5010         40.00         1.0638
1.34             1.50
60         2.145         0.6662         60.00         0.7092
3.02             1.00
80         4.293         0.4997         80.00         0.5319
8.07             0.75

    Sample rate/2  0.705 sec Nyquist period
    1/cutoff  1.42

Randy


----- Original Message -----
From: "Barry" 
To: 
Sent: Sunday, August 11, 2002 9:25 AM
Subject: Re: FFT


> Rolando
>     I'll contribute a little. As I understand it, any signal can be
> representated by a sum of sine waves of different frequencies and
> magnitudes. With the FFT, the math routine has selected multiples of 2 to
> speed up the calculation process. You  don't get as much of the frequency
> spectrum but it calculates faster. What you  see when you run an FFT is
the
> magnitude sum of the various sign waves ploted as a function of frequency
> for that given quake and your sensor.  I, as an example,  usually filter
> teleseismic events to remove frequencies below 0.003 hz and above 0.5 to 1
> hz ( so my files won't be so large.) . You should save events at a
sampling
> frequency twice the value of the highest frequency  of interest
(Nuquest ).
> I think what happens if you save higher frequencies than the sampling
rate,
> the sampling picks  points on different signal cycles (like a beat) and a
> higher frequency can look like a low one in the FFT.
> Regards
> Barry
>
> > > Larry et al,
> > > I am a newcomer -almost- in this list and an apprentice of the
> earthquakes
> > > sciences, I have been posting events at the PSN web page since late
May,
> > > having the good fortune to live in the middle of a very active area, I
> > have
> > > posted a few. As a beginner I need to learn a lot about many things, I
> > have
> > > received wonderful help from several PSN members, thank to them I am
> > > enjoying this very much. I would like to address some questions to the
> > group
> > > looking for some light in the area of what the FFT module of WINQUAKE
> is,
> > > I've used the filters in a very practical and blind way, so I have a
> > slight
> > > idea of what it can be used for,  but have no clue in the relationship
> > among
> > > the period of sensor and the freq of the event and the proximity of
> quake,
> > > etc, and the FFT screen, so I really need further assistance. Can
> someone
> > > give me some light, please? How can I find some info in the Internet,
> > book,
> > > etc.,? Your help would be very appreciated.
> > > Best regards from Fraijanes, Guatemala.
> > > Rolando Benitez
> > >
> > > __________________________________________________________
> > >
> > > Public Seismic Network Mailing List (PSN-L)
> > >
> > > To leave this list email PSN-L-REQUEST@.............. with
> > > the body of the message (first line only): unsubscribe
> > > See http://www.seismicnet.com/maillist.html for more information.
> > >
> >
> >
> > __________________________________________________________
> >
> > Public Seismic Network Mailing List (PSN-L)
> >
> > To leave this list email PSN-L-REQUEST@.............. with
> > the body of the message (first line only): unsubscribe
> > See http://www.seismicnet.com/maillist.html for more information.
> >
> >
>
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>

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Subject: WinPlotGPS
From: "Larry Cochrane"  cochrane@.............. 
Date: Mon, 12 Aug 2002 23:03:34 -0700

Hi Everyone,

A few months ago I started to work on a new program that uses the Location
Map Window code in WinQuake to plot the data from a GPS receiver on a map.
The program is now ready for beta testing.
While not directly related to earthquakes the program can be used to
calculate the height and position of your sensor using long term averaging.
To use the program you will need either a Motorola ONCORE receiver or any
GPS receiver the can output NMEA messages. More information about the
program and a download link can be found on this page
http://www.seismicnet.com/winplotgps/.

Regards,
Larry Cochrane
Redwood City, PSN


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Subject: DRIP (diamagnetically restored inverted pendulum)
From: Bobhelenmcclure@.......
Date: Wed, 14 Aug 2002 23:20:24 EDT

Hi everyone,

  A few weeks ago, I hatched a new idea for an old concept, the inverted 
pendulum, and made a demo model of it for study.  It consists of a graphite 
rod, 3 mm in diameter by 304 mm long, with 13 full turns of 1/8 diameter 
solder (20 grams) on top to provide the inertial mass.  The restoring force 
for this pendulum is provided by permanent magnets surrounding the graphite, 
and arranged to form a linear quadrupole field.  Graphite is diamagnetic, and 
is repelled by magnetic field gradients.  For a graphite rod immersed in a 
quadrupole field, this repulsive force is radially symmetric, and linearly 
proportional to the displacement of the rod from the magnet axis.  The 
restoring torque is proportional to the height of the magnet above the pivot 
point of the graphite rod.  By adjusting the height, one can get a long 
period pendulum, where the restoring torque is slightly stronger than the 
destabilizing gravity torque.

  Damping is provided by a sleeve made of 0.0045 inch thick aluminum foil 
salvaged from a deli pie plate.  Any amount of damping, from none to very 
over-damped, can be obtained by adjusting the penetration of the sleeve into 
the magnetic field.

  My present device is lacking the necessary position sensors, so I can tell 
you nothing about its performance as a tiltmeter type seismometer.  That will 
have to come later.  It should be able to sense horizontal ground motion and 
direction, if fitted out with a pair of othogonally oriented position 
sensors.

  I cut the top off of an empty LP gas bottle to form the support for the 
magnet.  The resulting cylinder is 8.25 inches tall and 2.75 inches O.D.  I 
put a bridge plate inside to form a resting place for the magnet.  The magnet 
and bridge are held in place by a coil spring between the magnet and inner 
wall.  The magnet can be easily axially aligned and centered, and can be 
adjusted up and down by sliding the spring, magnet, and bridge as a unit up 
and down within the cylinder.  A .375 inch hole was drilled in the bottom of 
the tank to allow the dully pointed tip of the graphite rod to pivot on the 
base plate.  No tilt adjustment is used.  Instead, the bottle is nudged about 
on the base plate until a point of balance is reached.  Fine adjustment is 
attained by very lightly tapping the base of the bottle with a pencil.  
Eventually, a top cover will be fabricated which will shield the pendulum 
from drafts and provide a structure for mounting the pickoffs. A small ball 
at the bottom end of the rod makes a better, more load bearing, pivot.  The 
graphite rod should be selected for straightness.  (You have to buy 12, so 
you can select the best.)

  The magnet is made up of 24 each 0.25 inch cube magnets of NdFeB.  Six 
magnets on each side form a 0.25 inch square opening of 1.5 inch length.  
Four spacers of 0.25 inch copper tubing hold the magnets in position as well 
as four 0.125 thick steel plates lap-jointed around the outside of the 
assembly.  The assembly is self-assembling (if you do it right) and self 
supporting, excepting for a tendency for the magnets to separate themselves 
axially.  Four brass bolts through the copper spacers keep the magnets 
axially confined.

  The natural period of this device is temperature sensitive, because the 
magnetic field is temperature sensitive.  Furthermore, the restoring force is 
a function of the square of the magnetic field, making the sensitivity even 
greater.  The very delicate balance of restoring force against gravity force 
causes the period to very temperature dependent.  Right now, the pendulum is 
set up on my basement floor on a base plate of Corian, set up for a period of 
5 seconds.  I will monitor the balance of the pendulum to see how well it 
remains centered over the next few days.

  The magnets were purchased from amazingmagnets.com and the graphite 
spectrographic grade rods from tedpella.com.

  I wish to acknowledge the help and advice of Chris Chapman and the 
encouragement provided by John Lahr, Meredith Lamb, and David Lamb in this 
endeavor.

Regards,  Bob McClure
Hi everyone,



  A few weeks ago, I hatched a new idea for an old concept, the inverted pendulum, and made a demo model of it for study.&
nbsp; It consists of a graphite rod, 3 mm in diameter by 304 mm long, with 13 full turns of 1/8 diameter solder (20 grams) on t
op to provide the inertial mass.  The restoring force for this pendulum is provided by permanent magnets surrounding the g
raphite, and arranged to form a linear quadrupole field.  Graphite is diamagnetic, and is repelled by magnetic field gradi
ents.  For a graphite rod immersed in a quadrupole field, this repulsive force is radially symmetric, and linearly proport
ional to the displacement of the rod from the magnet axis.  The restoring torque is proportional to the height of the magn
et above the pivot point of the graphite rod.  By adjusting the height, one can get a long period pendulum, where the rest
oring torque is slightly stronger than the destabilizing gravity torque.



  Damping is provided by a sleeve made of 0.0045 inch thick aluminum foil salvaged from a deli pie plate.  Any amount
 of damping, from none to very over-damped, can be obtained by adjusting the penetration of the sleeve into the magnetic field.




  My present device is lacking the necessary position sensors, so I can tell you nothing about its performance as a tiltme
ter type seismometer.  That will have to come later.  It should be able to sense horizontal ground motion and directi
on, if fitted out with a pair of othogonally oriented position sensors.



  I cut the top off of an empty LP gas bottle to form the support for the magnet.  The resulting cylinder is 8.25 inc
hes tall and 2.75 inches O.D.  I put a bridge plate inside to form a resting place for the magnet.  The magnet and br
idge are held in place by a coil spring between the magnet and inner wall.  The magnet can be easily axially aligned and c
entered, and can be adjusted up and down by sliding the spring, magnet, and bridge as a unit up and down within the cylinder.&n
bsp; A .375 inch hole was drilled in the bottom of the tank to allow the dully pointed tip of the graphite rod to pivot on the 
base plate.  No tilt adjustment is used.  Instead, the bottle is nudged about on the base plate until a point of bala
nce is reached.  Fine adjustment is attained by very lightly tapping the base of the bottle with a pencil.  Eventuall
y, a top cover will be fabricated which will shield the pendulum from drafts and provide a structure for mounting the pickoffs.
 A small ball at the bottom end of the rod makes a better, more load bearing, pivot.  The graphite rod should be selected 
for straightness.  (You have to buy 12, so you can select the best.)



  The magnet is made up of 24 each 0.25 inch cube magnets of NdFeB.  Six magnets on each side form a 0.25 inch square
 opening of 1.5 inch length.  Four spacers of 0.25 inch copper tubing hold the magnets in position as well as four 0.125 t
hick steel plates lap-jointed around the outside of the assembly.  The assembly is self-assembling (if you do it right) an
d self supporting, excepting for a tendency for the magnets to separate themselves axially.  Four brass bolts through the 
copper spacers keep the magnets axially confined.



  The natural period of this device is temperature sensitive, because the magnetic field is temperature sensitive.  F
urthermore, the restoring force is a function of the square of the magnetic field, making the sensitivity even greater.  T
he very delicate balance of restoring force against gravity force causes the period to very temperature dependent.  Right 
now, the pendulum is set up on my basement floor on a base plate of Corian, set up for a period of 5 seconds.  I will moni
tor the balance of the pendulum to see how well it remains centered over the next few days.



  The magnets were purchased from amazingmagnets.com and the graphite spectrographic grade rods from tedpella.com.



  I wish to acknowledge the help and advice of Chris Chapman and the encouragement provided by John Lahr, Meredith Lamb, a
nd David Lamb in this endeavor.



Regards,  Bob McClure

Subject: Re: DRIP (diamagnetically restored inverted pendulum)
From: "George Harris"  gjharris@............. 
Date: Wed, 14 Aug 2002 22:28:16 -0700


  ----- Original Message -----=20
  From: Bobhelenmcclure@..........
  To: psn-l@.................
  Sent: Wednesday, August 14, 2002 8:20 PM
  Subject: DRIP (diamagnetically restored inverted pendulum)


  My present device is lacking the necessary position sensors, so I can =
tell you nothing about its performance as a tiltmeter type seismometer.  =
That will have to come later.  It should be able to sense horizontal =
ground motion and direction, if fitted out with a pair of othogonally =
oriented position sensors.

  A suggestion from George Harris

  A very sensitive and inexpensive two axis sensor can be made as =
follows:

  Above the top surface of the pendulum, place an LED with the front =
surface=20
  flattened so that it become a point source about 1/4 inch above the =
surface.
  On the top surface cement a 6mm square mirror (stock H43866 from =
Edmund).
  On each of the four sides of the LED place small solar cells (stock =
980-0150
  from allied) in such a position that each will be half illuminated by =
the LED.

  The photocells can be connected in parallel, plus to minus, on the =
opposite sides across the inputs to a low noise operational amplifier =
(like an OP27 from Precision monolithics) with about a megohm in the =
feedback.  The resulting output is very sensitive (nanometers) and =
linear.

  To check the sensitivity, I mounted the assembly on a three point =
platform with
  a dial indicator on one end of the platform.  Tilting the platform by =
small motions of a support screw permits the accurate measurement of the =
anglular (or acceleration) sensitivity.









 


  
----- Original Message ----- 

  From:=20
  Bobhelenmcclure@....... 
  
  
Sent: Wednesday, August 14, =
2002 8:20=20
  PM

  
Subject: DRIP (diamagnetically =
restored=20
  inverted pendulum)

  


  
My present device is lacking the necessary =
position=20
  sensors, so I can tell you nothing about its performance as a =
tiltmeter type=20
  seismometer.  That will have to come later.  It should be =
able to=20
  sense horizontal ground motion and direction, if fitted out with a =
pair of=20
  othogonally oriented position sensors.

  
A suggestion from George =
Harris

  
 

  
A very sensitive and inexpensive two axis sensor =
can be=20
  made as follows:

  
 

  
Above the top surface of the pendulum, place an =
LED with=20
  the front surface 

  
flattened so that it become a point source about =
1/4 inch=20
  above the surface.

  
On the top surface cement a 6mm square mirror =
(stock H43866=20
  from Edmund).

  
On each of the four sides of the LED place small =
solar=20
  cells (stock 980-0150

  
from allied) in such a position that each will be =
half=20
  illuminated by the LED.

  
 

  
The photocells can be connected in parallel, plus =
to minus,=20
  on the opposite sides across the inputs=20
  to a low noise operational amplifier (like an OP27 from Precision =
monolithics)=20
  with about a megohm in the feedback.  The resulting output is =
very=20
  sensitive (nanometers) and linear.

  
 

  
To check the sensitivity, I mounted =
the assembly=20
  on a three point platform with

  
a dial indicator on one end of the=20
  platform.  Tilting the platform by small motions of a support =
screw=20
  permits the accurate measurement of the anglular (or acceleration)=20
  sensitivity.

  
 


Subject: Re: DRIP (diamagnetically restored inverted pendulum)
From: ChrisAtUpw@.......
Date: Fri, 16 Aug 2002 07:48:42 EDT

In a message dated 15/08/02, gjharris@............. writes:

> A very sensitive and inexpensive two axis sensor can be made as follows:
> 
> Above the top surface of the pendulum, place an LED with the front surface 
> 

> On the top surface cement a 6mm square mirror (stock H43866 from Edmund).
> On each of the four sides of the LED place small solar cells (stock 980-0150
> from allied) in such a position that each will be half illuminated by the 
> 

Hello George Harris,

      Nice to have some extra input! I am having a problem in visualising the 
optical layout you suggest and the orientation and position of the various 
components. Is the LED 'water clear' plastic or what, please? What size? Are 
they IR or visible?  
       When you cut the end off a plastic LED and polish the end, looking 
into it, you see a bright central square chip surrounded by a ring of light 
from the plastic case. Putting a mirror on the end just reflects most of the 
light back through the base.
       Is that any chance of a quick sketch / 'paint' drawing, please?

       Edmund optics seem to be at http://www.edmundoptics.com/  There is no 
response to H43866, but there is a 10 mm square surface mirror NT45-517 
@.......
  
> The photocells can be connected in parallel, plus to minus, on the opposite 
> sides across the inputs to a low noise operational amplifier with about a 
> megohm in the feedback.  The resulting output is very sensitive 
> 

      The photo output of LEDs varies exponentially with temperature and you 
get about a factor of five reduction in light output at a constant current if 
you increase the temperature from 0 C to 100 C. Since you can expect ambient 
changes of >10 C deg and the LEDs themselves can heat up considerably, the 
variations are significant. How do you stabilise the photo output please?

    Regards,

      Chris Chapman
In a message dated 15/08/02, gjharris@............. writes:



A very
 sensitive and inexpensive two axis sensor can be made as follows:



Above the top surface of the pendulum, place an LED with the front surface 

flattened so that it become a point source about 1/4 inch above the surface.




On the
 top surface cement a 6mm square mirror (stock H43866 from Edmund).

On each of the four sides of the LED place small solar cells (stock 980-0150

from allied) in such a position that each will be half illuminated by the LED.




Hello George Harris,



      Nice to have some extra input! I am having a problem in visualising the optical layout you s
uggest and the orientation and position of the various components. Is the LED 'water clear' plastic or what, please? What size?
 Are they IR or visible?  

       When you cut the end off a plastic LED and polish the end, looking into it, you see a 
bright central square chip surrounded by a ring of light from the plastic case. Putting a mirror on the end just reflects most 
of the light back through the base.

       Is that any chance of a quick sketch / 'paint' drawing, please?



       Edmund optics seem to be at http://www.edmundoptics.com/  There is no response to
 H43866, but there is a 10 mm square surface mirror NT45-517 @.......

  

The ph
otocells can be connected in parallel, plus to minus, on the opposite sides across the inputs to a low noise operational amplif
ier with about a megohm in the feedback.  The resulting output is very sensitive (nanometers) and linear.




      The photo output of LEDs varies exponentially with temperature and you get about a factor of
 five reduction in light output at a constant current if you increase the temperature from 0 C to 100 C. Since you can expect a
mbient changes of >10 C deg and the LEDs themselves can heat up considerably, the variations are significant. How do you sta
bilise the photo output please?



    Regards,



      Chris Chapman

Subject: ebay auction
From: BOB BARNS  royb1@........... 
Date: Fri, 16 Aug 2002 08:12:30 -0400

Hi gang,
  A friend has one of these-a nice piece of hardware:

KINETIC SYSTEMS MODEL SH-1 SEISMOMETER 
Item # 2130828594 
Ends Aug-19-02 19:47:15 PDT 

goto  ebay.com
Bob
__________________________________________________________

Public Seismic Network Mailing List (PSN-L)


Subject: Re: DRIP (diamagnetically restored inverted pendulum)
From: "George Harris"  gjharris@............. 
Date: Sat, 17 Aug 2002 17:11:23 -0700


  ----- Original Message -----=20
  From: ChrisAtUpw@..........
  To: psn-l@.................
  Sent: Friday, August 16, 2002 4:48 AM
  Subject: Re: DRIP (diamagnetically restored inverted pendulum)


  In a message dated 15/08/02, gjharris@............. writes:=20


    A very sensitive and inexpensive two axis sensor can be made as =
follows:=20

    Above the top surface of the pendulum, place an LED with the front =
surface=20
    flattened so that it become a point source about 1/4 inch above the =
surface.
    On the top surface cement a 6mm square mirror (stock H43866 from =
Edmund).=20
    On each of the four sides of the LED place small solar cells (stock =
980-0150=20
    from allied) in such a position that each will be half illuminated =
by the LED.


  Hello George Harris,=20

       Nice to have some extra input! I am having a problem in =
visualising the optical layout you suggest and the orientation and =
position of the various components. Is the LED 'water clear' plastic or =
what, please? What size? Are they IR or visible?  =20
        When you cut the end off a plastic LED and polish the end, =
looking into it, you see a bright central square chip surrounded by a =
ring of light from the plastic case. Putting a mirror on the end just =
reflects most of the light back through the base.=20
        Is that any chance of a quick sketch / 'paint' drawing, please?=20

        Edmund optics seem to be at http://www.edmundoptics.com/  There =
is no response to H43866, but there is a 10 mm square surface mirror =
NT45-517 @..........
   =20
  Response By George***************8

  The LED I used was the small clear type.  I sandpapered the surface =
until it was
  very close to the LED, then used finer sandpaper and polishing =
compound (tooth
  paste works) until it was bright.  This LED was mounted on a small PC
  board above the top surface of the pendulum looking down.  The spacing =
should be approximately 1/4 inch above the mirror which was attached to =
the upper
  surface.  The mirror used was 6 mm square (1/4 inch).  The resulting =
reflection is=20
  approximately a 1/2 inch square at the surface of the PC board. If now =
small silicon photosensors are placed on the same board approximately =
1/2 inch apart, they will each be illuminated on 1/2 of their surface =
when the mirror is centered. =20
  The sensors I used are about 3mm (1/8 inch) square and moung flat to =
the board.
    The photocells can be connected in parallel, plus to minus, on the =
opposite sides across the inputs to a low noise operational amplifier =
with about a megohm in the feedback.  The resulting output is very =
sensitive (nanometers) and linear.


       The photo output of LEDs varies exponentially with temperature =
and you get about a factor of five reduction in light output at a =
constant current if you increase the temperature from 0 C to 100 C. =
Since you can expect ambient changes of >10 C deg and the LEDs =
themselves can heat up considerably, the variations are significant. How =
do you stabilise the photo output please?=20

  Response**********

  Since the photocells are both half illuminated, the null is not =
sensitive to the
  output of the LED.  The changes in the LED ouput would only slightly =
effect the gain of the system.  Since I was using the sensor in a =
feedback mode to recenter
  the mass, this effect was minimal.  My system was in a heated area, so =
the=20
  LED output change was very small.

     Regards,=20

       Chris Chapman=20








 


  
----- Original Message ----- 

  From:=20
  ChrisAtUpw@....... 
  
  
Sent: Friday, August 16, 2002 =
4:48=20
  AM

  
Subject: Re: DRIP =
(diamagnetically=20
  restored inverted pendulum)

  

In a =
message dated=20
  15/08/02, gjharris@.............=20
  writes: 


  A very sensitive and inexpensive two axis sensor can be =
made as=20
    follows: 

Above the top surface of the pendulum, place an LED =
with=20
    the front surface 
flattened so that it become a point source =
about 1/4=20
    inch above the surface.
  On the top surface cement a 6mm square mirror (stock =
H43866 from=20
    Edmund). 
On each of the four sides of the LED place small solar =
cells=20
    (stock 980-0150 
from allied) in such a position that each will =
be half=20
    illuminated by the LED.
  


Hello George Harris, =


     Nice=20
  to have some extra input! I am having a problem in visualising the =
optical=20
  layout you suggest and the orientation and position of the various =
components.=20
  Is the LED 'water clear' plastic or what, please? What size? Are they =
IR or=20
  visible?   
      When you cut =
the end=20
  off a plastic LED and polish the end, looking into it, you see a =
bright=20
  central square chip surrounded by a ring of light from the plastic =
case.=20
  Putting a mirror on the end just reflects most of the light back =
through the=20
  base. 
      Is that any chance of a =
quick=20
  sketch / 'paint' drawing, please?=20
  

      Edmund optics seem to be =
at=20
  http://www.edmundoptics.com/  There is no response to H43866, but =
there=20
  is a 10 mm square surface mirror NT45-517 @....... 
  

  
Response By George***************8

  
 

  
The LED I used was the small clear type.  I sandpapered the =
surface=20
  until it was

  
very close to the LED, then used finer sandpaper and polishing =
compound=20
  (tooth

  
paste works) until it was bright.  This LED was mounted on a =
small=20
  PC

  
board above the top surface of the pendulum looking down.  =
The=20
  spacing should be approximately 1/4 inch above the mirror which =
was=20
  attached to the upper

  
surface.  The mirror used was 6 mm square (1/4 inch).  =
The=20
  resulting reflection is 

  
approximately a 1/2 inch square at the surface of the PC =
board. If=20
  now small silicon photosensors are placed on the same board =
approximately 1/2=20
  inch apart, they will each be illuminated on 1/2 of their surface when =
the=20
  mirro