Hi Doug,

As you read, John Evans is breaking some new ground with the
new acceleration sensors.

To get to the reports that John Evans mentioned, first
 ftp andreas.wr.usgs.gov
Then
 cd pub/outgoing/jrevans/OFR_98_109
  for the first report, and
 cd pub/outgoing/jrevans/OFR_98_586
  for the second one.
  
I've also put PDF and MS WORD97 versions of the first report here:

http://geohazards.cr.usgs.gov/evans/ofr_98_109.html

Good luck with your monitoring!

JCLahr

******

>From: "John R. Evans" 
>To: doug@.............
>Subject: Strong motion for Santa Cruz mountain home


Doug,

I have a design for a good but relatively inexpensive (ca.
$500 parts for three components) strong-motion sensor.  You
will need four channels (the fourth for temperature) if you
use it.  Do an old-fashioned anonymous ftp() to
andreas.wr.usgs.gov and retrieve either the PC (.zip) or the
Unix (.Z's) version of USGS Open-file Report 98-109 (design),
and possibly 98-586 (what we're doing with them in Oakland):

   /ftp/pub/outgoing/jrevans/OFR_98_109
   /ftp/pub/outgoing/jrevans/OFR_98_586

PEPP would be interesting and useful too (Susan Schwartz at
UCSC would like some teleseismic records, I'm sure, to look
at anisotropy) but strong-motion is my passion (and bias!).
The PEPP instrument will peg, I believe, for strong motion.
Either way, good luck.

--John
jrevans@........

Doug,

Just got down to your follow-up message, again forwarded to
me by John Lahr.

The ADXL devices are certainly adequate for shut-off valves
and a microcontroller with them could be used to trigger on
something more subtle than peak acceleration (peak velocity
is a better predictor of damage, for example).  We would not
sneeze at records from them either, but they are rather noisy
by our standards and really only about a 9-bit sensor (when
comparing broadband peak-to-peak noise to a +/-2 g relevant
range in earthquakes ... well, some say +/-3 g is wiser very
close to a fault).  Useful, but the design I sent you in the
previous e-mail is a true 16-bit sensor and therefore produces
much more valuable seismograms.  It can be stretched beyond
the +/-2 g limit, but the maker does not guarantee linearity
(probably adequate to +/-2.5 g anyway).

My TREMOR Project is aimed at something similar to your sug-
gestion for a strong-motion instrument at many internet nodes.
It looks like the spatial variability of shaking requires an
instrument at least every km to get a decently accurate map
of shaking strength.  We're currently using CDPD (cell phone
internet) but I have serious doubts about its reliability after
a big event (mainly because ground lines to the cell phone base
stations are vulnerable).  A more robust private telemetry,
such as ISM spread spectrum, is a better long-term solution.
We are currently exploring a particularly interesting version.
Stay tuned.

Good luck,
John
jrevans@........


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