PSN-L Email List Message

Subject: Re: seismograph polarity
From: Karl Cunningham karlc@..........
Date: Sun, 15 Jul 2001 11:17:22 -0700

Angel --

I got the following from Edward Cranswick on July 30, 1997.


>   Ground Motion: Down to Up, i.e., upward, is positive.
>   Ground Motion: South to North, i.e., towards the North, is postive.
>   Ground Motion: West to East, i.e., towards the East, is postive.
> The above is a convention we use here at our USGS group in Golden, CO,
> that chases earthquakes.  The important thing is that the motion of the
> ground in one linear direction is ultimately represented by some kind of
> wiggly line on paper or a screen (computer, CRT, etc.), and as long as
> one knows that when the line moves up or down, the ground moves back and
> forth correspondingly, then one is getting started in using one's
> instrument to find out what the Earth is doing.
> -Edward

--On Sunday, July 15, 2001 12:24 -0500 "angel@chiriqui" 

> Hi All,
> If I tap a N/S horizotal geophone from the north which way should the
> trace go?
> angel
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Larry Cochrane <cochrane@..............>