In a message dated 2008/05/26, tchannel1@............ writes:

> I plan on changing the period from 20 seconds to another number, not sure 
> what that number will be.   What I want to see, is how it records at different 
> period settings.
> I know the advantages of the 20 seconds.  The disadvantage is it misses many 
> other smaller earthquakes.
> My question:  Before I try other period numbers..........Have you tried 
> this, and what were the results?
> I really don't know what the result would be.

Hi Ted,

       If your Lehman is working properly, it should see all signals between 
the natural resonant period, at say 20 seconds and the low pass fiolter of 
your amplifier at 10 Hz.

       If you set the period to 10 seconds, it will only record signals 
between 10 seconds and 10 Hz. It will have about 1/4 theprevious sensitivity to 20 
second Love waves. 

       You WILL NOT see any more Earthquakes this way.

       Remember that Lehmans are directional? Could this be why you are 
missing some quakes? What quakes have you missed and why do you think you should 
have recorded them?
       An alternative is that your suspension may be sticking and preventing 
the arm from moving freely. You may then only see larger quakes.
       Can you remind me what suspensions, top and bottom, you are using, 
please?
       Do you see the normal 4 to 8 second microseisms OK?

       Regards,

       Chris Chapman   
In a me=
ssage dated 2008/05/26, tchannel1@............ writes:



I plan on changing the period f=
rom 20 seconds to another number, not sure what that number will be. &n=
bsp; What I want to see, is how it records at different period settings.
I know the advantages of the 20 seconds.  The disadvantage is it misse=
s many other smaller earthquakes.

My question:  Before I try other period numbers..........Have you trie=
d this, and what were the results?

I really don't know what the result would be.




Hi Ted,



       If your Lehman is working properly, it=20=
should see all signals between the natural resonant period, at say 20 second=
s and the low pass fiolter of your amplifier at 10 Hz.



       If you set the period to 10 seconds, it=
 will only record signals between 10 seconds and 10 Hz. It will have about 1=
/4 theprevious sensitivity to 20 second Love waves. 



       You WILL NOT see any more Earthquakes t=
his way.



       Remember that Lehmans are directional?=20=
Could this be why you are missing some quakes? What quakes have you missed a=
nd why do you think you should have recorded them?

       An alternative is that your suspension=20=
may be sticking and preventing the arm from moving freely. You may then only=
 see larger quakes.

       Can you remind me what suspensions, top=
 and bottom, you are using, please?

       Do you see the normal 4 to 8 second mic=
roseisms OK?



       Regards,



       Chris Chapman