PSN-L Email List Message

Subject: Re: Spring for AS-1 type vertical seismometer
From: Brett Nordgren brett3nt@.............
Date: Mon, 21 Nov 2011 08:50:59 -0500

Hi Dave,

I agree, Richard has made a very nice looking instrument.

Regarding noise, I think it's the other way around.  Generally the 
verticals are considerably less sensitive to local disturbances of 
the ground (though much more sensitive to temperature and barometric 
pressure changes).  Here's a couple of traces captured from the 
vertical channel (top trace) and one of the horizontal channels of a 
Nanometrics Trillium Compact 120 three-axis instrument, operated by 
Dave Nelson in 
The wind was blowing that day and was shaking the ground quite a 
bit.  That's typical of what you would normally see.

Good verticals can be a lot harder to build, but they can perform 
much better in the sorts of locations that are likely to be available.

Although his instruments are located very close to the 
Dave gets very good results with his verticals, whose 
can look as good or better than the USGS helicorder 

As we continue to test new designs, it appears that his vertical 
instruments' sensitivity, as determined by their internal noise, may 
possibly be a little better than his Trillium.  More testing in the works.


At 04:48 AM 11/21/2011, you wrote:

>Hi Richard
>      great looking sensor :)
>  I have pondered the construction of a vertical sensor but have 
> always thought they
>  picked up too much local "people noise" to be really successful, 
> particularly in
>suburbia.  I wonder how you have found it ? maybe you have a reasonably quiet
>   going by the seismograms it obviously works very well
>    I would like to see some more information on how your pivot is 
> assembled, if
>that is possible please :)  I just couldnt quite make it all out in the pic.
>Dave Nelson


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