Hi,

I've briefly joined the list because I've been told (and I see that it is true)
that some list 
subscribers have shown interest in my invention. Dealing with some of the points
......
* It is intended for strong motion sensing, so probably would not have the high
sensitivity and low 
noise demanded in teleseismic studies.
* The technology is based on a micromachined silicon chip. I can't tell you
too much about it as the 
device has been commercialized. But it does better than the capacitance sensing
that airbag 
sensors use, in terms of noise. It uses a piezoresistive bridge sensing beam
deformation.
* It is intended as a plug-in replacement for common accelerographs - the ad
hoc power supply 
voltage is 12v dc, the ad hoc sensitivity is 1.25 volt/g, and it is dc to 50Hz.

* The prime advantage is cheap installation, and the small size is the key to
that because it 
reduces the force required to push it into the ground.
* Installation is simple and cheap. Our web page http://www.gns.cri.nz/earthact/probe/index.html

shows installation at Texcoco, Mexico. Five probes were installed there at 40m,
30m, 20m, 10m 
and 2m below the ground in the course of a single day. Work out the price advantage
for yourself!
* I have run two vertical arrays of these probes in New Zealand in the last
few years. The arrays 
have given plenty of direct empirical evidence of the variation of motion with
depth, for several felt 
earthquakes.
* The appropriate venue to follow the topic up in is to email s-probe@...........
but it is essential 
to use the word "subsurface" in the subject line or our spam blocker will reject
it.

I think the efforts of PSN are valuable.

Regards,
Bill Stephenson



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