Hi Jan,

Perhaps.....the most important aspect is,....what kind of
terrain and/or space do you have available....i.e, city/country,
to place any seismo on.  Any house crawlspace available, or
garage, shed, or least disturbed area of land around?  One
will have to make "do" with what they have for placement.
If you do indeed have bedrock, that would be a plus....if...its
convenient and adaptable for a seismic "vault".  If you have
loose soil, the best remote and least watered/susceptible
area would be best.

The best material seems to be a "pier" of concrete, that can
be inside/outside weather enclosed and somewhat isolated from
domestic seismic sources of "noise"......or....if not possible
to do so, one would have to live with the noise it generates;
which is usually easy to denote with time/experience.  The
pier usually needs to "fit" the area required by the sensor/s
anticipated.  The thickness of the concrete slab can be
debated I suppose, but I'd try for whatever depth/thickness
you can squeeze in the spot you chose.  I use about a 7-8"
thickness of my three piers....which are in reality cast concrete
pavers stacked together but layered in the joints and surfaces
with real concrete.  I chose this as it was near impossible to
mix massive concrete on my knees under the house, let alone
move all the sand/concrete therein.  For myself, I elected to
also use thick mylar sheet under the piers, to limit water
absorbion into the piers.  I even used a water repellent paint
on the pier/s to limit water absorbtion.  Even after completion,
you can expect a period of time before the piers stabilize from
curing....perhaps acouple months.  If you can make the pier
thickness even greater than say...6 inches thick, I'd do so.  Do
not use iron, steel in the pier.

Personally I live in Denver, and in a city lot.....so, I use my
house soil crawlspace for pier/seismometer placements.  I
also enclosed the piers with walls and insulation to somewhat
limit temperature excursion that do occur.  Among the PSN
members....we kind of all utilize whats available.....

So....in a way....everything gets back to what space you
have now that could be utilized.  Next, the physical size of
your anticipated seismos you're planning on building/using.

I think you're right to get into the seismo housing/piers aspect
right off the bat.....if one doesn't; than they will get into alot of
soil tilt, water, weather, temperature  related problems that will
make any consistent seismic monitoring rather useless otherwise.
Suggest that any pier/containment is well built and temperature
insulated; this can take time, but it would pay off in the long
run.

Outside of the above,.....what kind of seismic sensors are you
planning on using.....the instrumentation sensor aspect is always
interesting.

Take care, Meredith Lamb

"Jan D. Marshall" wrote:

> I am starting to design my sensors and electronics and have decided
> that I understand the requirments there pretty well -- what I don't
> have a very good understanding on is what do I need for a base or
> foundation to set the sensors on.  What type of mass does it need?
> does it need to set on bedrock?  I do not have any cement slab floors.
> Thanks Jan D. Marshall
> Nampa, Idaho
> jandmarshall@............
>
>
>



Hi Jan,
Perhaps.....the most important aspect is,....what kind of

terrain and/or space do you have available....i.e, city/country,

to place any seismo on.  Any house crawlspace available, or

garage, shed, or least disturbed area of land around?  One

will have to make "do" with what they have for placement.

If you do indeed have bedrock, that would be a plus....if...its

convenient and adaptable for a seismic "vault".  If you have

loose soil, the best remote and least watered/susceptible

area would be best.
The best material seems to be a "pier" of concrete, that can

be inside/outside weather enclosed and somewhat isolated from

domestic seismic sources of "noise"......or....if not possible

to do so, one would have to live with the noise it generates;

which is usually easy to denote with time/experience.  The

pier usually needs to "fit" the area required by the sensor/s

anticipated.  The thickness of the concrete slab can be

debated I suppose, but I'd try for whatever depth/thickness

you can squeeze in the spot you chose.  I use about a 7-8"

thickness of my three piers....which are in reality cast concrete

pavers stacked together but layered in the joints and surfaces

with real concrete.  I chose this as it was near impossible to

mix massive concrete on my knees under the house, let alone

move all the sand/concrete therein.  For myself, I elected to

also use thick mylar sheet under the piers, to limit water

absorbion into the piers.  I even used a water repellent paint

on the pier/s to limit water absorbtion.  Even after completion,

you can expect a period of time before the piers stabilize from

curing....perhaps acouple months.  If you can make the pier

thickness even greater than say...6 inches thick, I'd do so. 
Do

not use iron, steel in the pier.
Personally I live in Denver, and in a city lot.....so, I use my

house soil crawlspace for pier/seismometer placements.  I

also enclosed the piers with walls and insulation to somewhat

limit temperature excursion that do occur.  Among the PSN

members....we kind of all utilize whats available.....
So....in a way....everything gets back to what space you

have now that could be utilized.  Next, the physical size of

your anticipated seismos you're planning on building/using.
I think you're right to get into the seismo housing/piers aspect

right off the bat.....if one doesn't; than they will get into alot
of

soil tilt, water, weather, temperature  related problems that
will

make any consistent seismic monitoring rather useless otherwise.

Suggest that any pier/containment is well built and temperature

insulated; this can take time, but it would pay off in the long

run.
Outside of the above,.....what kind of seismic sensors are you

planning on using.....the instrumentation sensor aspect is always

interesting.
Take care, Meredith Lamb
"Jan D. Marshall" wrote:

I
am starting to design my sensors and electronics and have decided that
I understand the requirments there pretty well -- what I don't have a very
good understanding on is what do I need for a base or foundation to set
the sensors on.  What type of mass does it need? does it need to set
on bedrock?  I do not have any cement slab floors. Thanks
Jan D. Marshall

Nampa, Idaho

jandmarshall@............