[time-nuts] USGS: GPS for seismic work
Rex
rexa at sonic.net
Sun May 20 02:55:39 UTC 2012
I was at the USGS open house for a couple hours. My first time to go.
Was also my first time to see a commercial choke ring GPS antenna up
close. Was interesting to see the antenna shifted a few inches and
causing a step function on the internet screen where they where
monitoring it along with a few permanent logging station antennas that
were (fortunately) stable while we were watching.
Also enjoyed seeing a hand held XRF Spectrometer (Xray Fluorescence) for
identifying the material in random samples. And good to chat with the
guy who carried it around Afghanistan for the last few years helping
(the Afghanies?) learn what neat stuff their country contains. He also
had an entertaining story about shopping for silver items -- "90%
silver, sir." He pulls the XRF out of his pack and scans to find more
like 20% silver.
Quite a few interesting discussions with several people around the
place. Also bought a nice large wall map of California with nice relief
view of the mountains for $9.
Well worth the drive from San Jose.
On 5/19/2012 6:09 PM, Hal Murray wrote:
> It wasn't hard to find the right people at the Open House.
>
> GPS is interesting for big quakes.
>
> Most seismometers measure acceleration. It's a double integration to get
> displacement which is what they are used to working with. Big quakes last
> longer which leads normal seismometers to get into troubles with drift. GPS
> doesn't have any drift problems. The cross over is somewhere in the mag 7-8
> range.
>
> Japan has a large earthquake warning system. On the big tsunami of last
> year, they weren't looking for long enough. They estimated 7.9. In
> hindsight, they probably could have gotten better data sooner by using GPS.
>
> This news story says that they can see the disturbance in the ionosphere.
> http://www.cbc.ca/news/technology/story/2012/04/23/f-tsunami-research.html
>
>
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