Dear PSN networkers,

FYI; check out this story on Moon-quake analysis and a retro study 
yielding new conclusions AND the value of keeping our seismograms 
archived and preserved properly


          February 15, 2005 (NYT) Scientists Find Deeper Meaning for
          Moon Rumblings

http://www.nytimes.com/2005/02/15/science/space/15moon.html?ex=1109221200&en=ccd4da907f98d966&ei=5070 


I agree with the previous 2 contributors - Microseisms are not just 
"noise', they tell a story about our ocean/ weather environment and 
perhaps, we should be more closely logging the amplitude/ frequency (6 
hourly) to see the effect of the "greenhouse phenomena"  and comparing 
it to similar months, say 10 years ago.

Historically speaking (pre radar) microseismic measurements were the 
forecaster for trcking Cyclones and hurricanes.
With rising sea levels (increased water mass), perhaps the oceans will 
change their resonant frquency (7hz) ???
Perhaps PSN "amateur seismologists" could keep a watch on that?

Just some thoughts...I find the pSN network is a great experimenter; 
something that is lost these days where everything seismological seems 
to be done on a VDU and off-the-shelf instrumentation kills experimentation.

cheers
col lynam
volunteer observor, QUAKES group, ESSCC centre, University of 
Queensland, Australia
http://www.esscc.uq.edu.au


Bob Hancock wrote:

>One of the sources of microseism is wave action at shore lines.  There is a
>public US Navy web site that gives current wave heights and projections from
>12 hours to 144 hours, world wide.  It is useful in seeing where the wave
>activity is when you see large microseisms.
>
>	https://www.fnmoc.navy.mil/PUBLIC/WAM/all_glbl.html
>
>Bob Hancock
>
>
>-----Original Message-----
>From: psn-l-request@.............. [mailto:psn-l-request@............... On
>Behalf Of Connie and Jim Lehman
>Sent: Thursday, February 24, 2005 08:06
>To: psn-l@..............
>Subject: Re: Microseism filter
>
>PSN & Davids/2
>     Regrets to hear of necessity to tune out microseisms.  I have always
>considered them a friend,--they are always there--a quick check of system,
>performance-- and really quite entertaining as changes occur
>daily--sometimes hourly.  Certainly in a classroom or a Science Center
>setting the presense of microseisms adds to the total picture of Earth
>activities.  My location inland in Virginia about 100 miles
>from the Atlantic puts me in range of a host of activity on the Eastern
>Seaboard --based of course on long period performance that I havc used.
>Tropical storms show the moment they reach Florida and move northward to New
>England or North Atlantic--  and  the normal flow of barometric highs & lows
>in the southeast to northeast trending storm tracks through VA.  Then for
>whatever reason in summer months, microseismic amplitudes go low for weeks
>at a time--an opportunity to crank up the gain a bit.  I try to keep
>microseisms about 1/4 in. in amplitude most of the time.
>    Microseisms build to obnoxious amplitudes only as hurricanes move up the
>east coast usually east of us, and there have been times where I closed down
>recording for 10 hours or so.  Perhaps you folks by oceanside locations have
>to live with more of this "pounding" a lot of the time.
>   I am curious what affect filtering of microseisms would have on an
>earthquakes profile--expecially the first arrivals of P-waves that often
>don't appear to have periods too far removed from the cluster of 3-7sec
>periods of typical microseisms.
>----- Original Message -----
>From: "David H. Youden" 
>To: 
>Sent: Thursday, February 24, 2005 7:07 AM
>Subject: Re: Microseism filter
>
>
>  
>
>>Dave,
>>
>>Tell me more about your filter. I live on the East coast, and am
>>troubled by the level of microseisms. I have messed a bit with switched
>>capacitor circuits in the past, but for different purposes. Could you
>>send a circuit diagram directly to me? Or point me to the chip you used
>>so I can puzzle out my own filter.
>>
>>Dave...
>>
>>Dave Nelson wrote:
>>
>>    
>>
>>>I have recently added a Russian ASMET -1V MET broadband seismometer to
>>>my setup. As I live near the coast the microseism level was dominating
>>>the noise backgrond to the extent that earthquakes of interest were
>>>being lost in the " noise". The microseism spectrum is very distinct
>>>and I felt  its elimination  would not seriously effect the earthquake
>>>detection capability .
>>>
>>> I have developed a simple filter based on switched capacitor
>>>technology that virtualy eliminates the microseism background. The
>>>filter has no critical componants or  capacitors and is tuned by a
>>>clock frequency. The Q is 0.5 which gives roughly an octave bandwidth
>>>centered at 0.015 hz or 6.6 seconds . Since the center frequncy is
>>>clock dependant it can be shifted arbitarily but 6.6 seconds seems to
>>>work very well. The filter is placed directly ahead of the A/D at the
>>>highest voltage swing  level in the system to avoid adding noise.
>>>Just two wires -- in and out (plus power of course).
>>>
>>>The results are very good, the harmonic like signal from microseism is
>>>gone and the effective signal to noise ratio of eathquakes is
>>>significantly better. The spectrum has a deep null at 6.6 seconds
>>>instead of a  dominant peak .
>>>
>>>I know this kind of spectrum shaping can be easily done in software
>>>but that is usually beyond the scope of an amateur or computer dum-
>>>dum like me. The whole thing is  two IC's and a 15 hz clock generator.
>>>( 100 times the center frequency)
>>>
>>>The Russian seismometer is truely amazing. Virtually plug and play --
>>>four wires ,no adjustments or critical setup. The respose is
>>>advertised to 20 seconds but seems to respond well to over 100 seconds
>>>on the low end and too well to be useful ,given the urban background
>>>noise ,at the high frequency end. I have another swiched capacitor low
>>>pass filter switchable to 5, 2.5 and 1.25 hz. to control the high end
>>>cutoff.
>>>
>>>My setup also includes 3 axes of short period based on HS-10-1  1 hz
>>>seismometers that I found in a surplus store. I am using Amaseis and
>>>experimenting with Seismowin for analysis and display.
>>>
>>>I am a retired aerospace engineer who spent too much of my career in
>>>management and I am having a ball doing the seismology thing.Good to
>>>be back doing some development and putting the old brain to work. I
>>>intend to do some seismometer development as my next project -- I have
>>>some ideas for some different ,but not outrageous, concepts which
>>>may ( or may not ) work.
>>>
>>>I would be glad to correspond with anyone interested in or commenting
>>>on what I am doing.
>>>
>>>
>>>Dave Nelson   ( California not New Zealand)
>>>      
>>>
>>__________________________________________________________
>>
>>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.
>  
>



  
  


Dear PSN networkers,



FYI; check out this story on Moon-quake analysis and a retro study
yielding new conclusions AND the value of keeping our seismograms
archived and preserved properly

February 15, 2005 (NYT) Scientists Find Deeper Meaning for Moon
Rumblings
http://www.nytimes.com/2005/02/15/science/space/15moon.html?ex=1109221200&en=ccd4da907f98d966&ei=5070



I agree with the previous 2 contributors - Microseisms are not just
"noise', they tell a story about our ocean/ weather environment and
perhaps, we should be more closely logging the amplitude/ frequency (6
hourly) to see the effect of the "greenhouse phenomena"  and comparing
it to similar months, say 10 years ago.



Historically speaking (pre radar) microseismic measurements were the
forecaster for trcking Cyclones and hurricanes.

With rising sea levels (increased water mass), perhaps the oceans will
change their resonant frquency (7hz) ???

Perhaps PSN "amateur seismologists" could keep a watch on that?



Just some thoughts...I find the pSN network is a great experimenter;
something that is lost these days where everything seismological seems
to be done on a VDU and off-the-shelf instrumentation kills
experimentation.



cheers

col lynam

volunteer observor, QUAKES group, ESSCC centre, University of
Queensland, Australia

http://www.esscc.uq.edu.au





Bob Hancock wrote:


  
One of the sources of microseism is wave action at shore lines.  There is a
public US Navy web site that gives current wave heights and projections from
12 hours to 144 hours, world wide.  It is useful in seeing where the wave
activity is when you see large microseisms.

	https://www.fnmoc.navy.mil/PUBLIC/WAM/all_glbl.html

Bob Hancock


-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@..............] On
Behalf Of Connie and Jim Lehman
Sent: Thursday, February 24, 2005 08:06
To: psn-l@..............
Subject: Re: Microseism filter

PSN & Davids/2
     Regrets to hear of necessity to tune out microseisms.  I have always
considered them a friend,--they are always there--a quick check of system,
performance-- and really quite entertaining as changes occur
daily--sometimes hourly.  Certainly in a classroom or a Science Center
setting the presense of microseisms adds to the total picture of Earth
activities.  My location inland in Virginia about 100 miles
from the Atlantic puts me in range of a host of activity on the Eastern
Seaboard --based of course on long period performance that I havc used.
Tropical storms show the moment they reach Florida and move northward to New
England or North Atlantic--  and  the normal flow of barometric highs & lows
in the southeast to northeast trending storm tracks through VA.  Then for
whatever reason in summer months, microseismic amplitudes go low for weeks
at a time--an opportunity to crank up the gain a bit.  I try to keep
microseisms about 1/4 in. in amplitude most of the time.
    Microseisms build to obnoxious amplitudes only as hurricanes move up the
east coast usually east of us, and there have been times where I closed down
recording for 10 hours or so.  Perhaps you folks by oceanside locations have
to live with more of this "pounding" a lot of the time.
   I am curious what affect filtering of microseisms would have on an
earthquakes profile--expecially the first arrivals of P-waves that often
don't appear to have periods too far removed from the cluster of 3-7sec
periods of typical microseisms.
----- Original Message -----
From: "David H. Youden" <dyouden@.............>
To: <psn-l@..............>
Sent: Thursday, February 24, 2005 7:07 AM
Subject: Re: Microseism filter


  
  

    
Dave,

Tell me more about your filter. I live on the East coast, and am
troubled by the level of microseisms. I have messed a bit with switched
capacitor circuits in the past, but for different purposes. Could you
send a circuit diagram directly to me? Or point me to the chip you used
so I can puzzle out my own filter.

Dave...

Dave Nelson wrote:

    
    

      
I have recently added a Russian ASMET -1V MET broadband seismometer to
my setup. As I live near the coast the microseism level was dominating
the noise backgrond to the extent that earthquakes of interest were
being lost in the " noise". The microseism spectrum is very distinct
and I felt  its elimination  would not seriously effect the earthquake
detection capability .

 I have developed a simple filter based on switched capacitor
technology that virtualy eliminates the microseism background. The
filter has no critical componants or  capacitors and is tuned by a
clock frequency. The Q is 0.5 which gives roughly an octave bandwidth
centered at 0.015 hz or 6.6 seconds . Since the center frequncy is
clock dependant it can be shifted arbitarily but 6.6 seconds seems to
work very well. The filter is placed directly ahead of the A/D at the
highest voltage swing  level in the system to avoid adding noise.
Just two wires -- in and out (plus power of course).

The results are very good, the harmonic like signal from microseism is
gone and the effective signal to noise ratio of eathquakes is
significantly better. The spectrum has a deep null at 6.6 seconds
instead of a  dominant peak .

I know this kind of spectrum shaping can be easily done in software
but that is usually beyond the scope of an amateur or computer dum-
dum like me. The whole thing is  two IC's and a 15 hz clock generator.
( 100 times the center frequency)

The Russian seismometer is truely amazing. Virtually plug and play --
four wires ,no adjustments or critical setup. The respose is
advertised to 20 seconds but seems to respond well to over 100 seconds
on the low end and too well to be useful ,given the urban background
noise ,at the high frequency end. I have another swiched capacitor low
pass filter switchable to 5, 2.5 and 1.25 hz. to control the high end
cutoff.

My setup also includes 3 axes of short period based on HS-10-1  1 hz
seismometers that I found in a surplus store. I am using Amaseis and
experimenting with Seismowin for analysis and display.

I am a retired aerospace engineer who spent too much of my career in
management and I am having a ball doing the seismology thing.Good to
be back doing some development and putting the old brain to work. I
intend to do some seismometer development as my next project -- I have
some ideas for some different ,but not outrageous, concepts which
may ( or may not ) work.

I would be glad to correspond with anyone interested in or commenting
on what I am doing.


Dave Nelson   ( California not New Zealand)
      
    
    
__________________________________________________________

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.