[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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