Hi Brett

  Thats interesting, as I though because most manmade local noise is 
vertically polarised, the main one ... people walking around, then its 
going to be easier to pick up on the vertical seismo.

well looks like I'm going to have to build one and see how it goes  :)

Richard, any chance of a pic with a bunch of measurements on it please
so I can get an idea of some dimensions of the various bits and close ups
of the hinge section
just email direct to me if possible

thanks lots
Dave


At 08:50 AM 21/11/2011 -0500, you wrote:
>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 
>California.   http://bnordgren.org/seismo/H_vs_V_-_Trillium_120.jpg
>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 
>house  http://bnordgren.org/seismo/IMG_1383s.jpg
>Dave gets very good results with his verticals, whose 
>traces  http://bnordgren.org/seismo/gif_images.htm
>can look as good or better than the USGS helicorder 
>plots.  http://aslwww.cr.usgs.gov/Seismic_Data/telemetry_data/ANMO_24hr.html
>
>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.
>
>Regards,
>Brett

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