[time-nuts] GPS, USGS Early Earthquake Warning
Hal Murray
hmurray at megapathdsl.net
Mon Apr 30 20:00:28 UTC 2012
tvb at LeapSecond.com said:
> Related to that, are there any seismometer experts on the list? I've always
> wondered why they don't augment the extremely sensitive detectors with less
> sensitive detectors? Of course a really good detector will overload; so just
> co-locate cheap detectors that are 40 and 80 dB less sensitive. That way you
> get a clean signal no matter how close or far the epicenter is from the
> detector.
I'm not a seismometer expert, but I live/worked close to the USGS Menlo Park
campus.
A couple days after the 1989 Loma Prieta earthquake, I wandered over there to
see if there was anything interesting for people like me to see. I was in a
glass enclosed walkway between two buildings. They had a long (20 ft?)
seismograph printout taped up high on one side. The first foot or two had
obviously saturated. There was a guy next to me who looked like he might
know something, so I asked, roughly, "Don't they have stations with the
amplification turned down so it doesn't saturate?" He gave me a dirty look
and said "That was the low gain channel."
I think there are two issues with saturation. One is the electronics and
communication channel. The other is the instrument itself.
There is probably a seismic-nuts list someplace. There is a lot of good work
going on in that area.
My favorite seismic URL is:
The Yosemite Rock Fall of July 10, 1996
UC Berkeley Seismographic Station, Earthquake of the Week
http://seismo.berkeley.edu/seismo/events_of_interest/yosemite/eoi_yos.html
For only slightly-geeky amateur seismology, try
QCN Quake-Catcher Network
http://qcn.stanford.edu/
For $50 you can get a USB connected seismometer. They provide software that
will plug it into their data collection setup.
Here is a good note:
http://qcn.stanford.edu/qcn-detects-earthquake-in-seconds
Some/many modern fancy cell phones include accelerometers. There is at least
one app that turns your phone into a seismometer and displays a graph.
--
These are my opinions, not necessarily my employer's. I hate spam.
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