Direct burial ( Uncased hole) installation method
The direct burial (also known as uncased hole) method is used for a shallow, low-cost
deployment. It is used for temporary installations or for installations in remote areas that are
inaccessible to a drill truck, or simply to save on installation costs. Saving cost on installation
allows you to install more stations within a similar budget. This is important because the size
and density of the network is just as important as the quality of each individual station. See
"Installing a Trillium Compact Posthole in an Uncased Hole (Direct Burial)" below
.
Cased hole installation method
The cased hole method is used for deeper installations in bedrock. This type of installation
improves noise performance but it costs more and requires access by a drill truck. This
method of installation is applicable to permanent seismic observatory stations. See
a Trillium Compact Posthole in a Cased Hole" on page 24
2.7.1 Installing a Trillium Compact Posthole in an Uncased Hole
(Direct Burial)
The hole should be a minimum of 1 meter deep and have a diameter large enough to
accommodate the instrument, which has a diameter of 97 mm. The minimum hole depth will
allow the instrument to be covered by of fill once the installation is complete. This backfill
creates a buffer between the installation and the surface, shielding it from temperature
change and weather. In general, greater depth produces better results with all other things
being equal.
Use the following steps to install a Trillium Compact Posthole seismometer in an uncased hole:
Ensure that the bottom of the hole is sufficiently level for your application. For best
results, the Trillium Compact Posthole seismometer should be as level as possible. For
deep holes, this may require the use of self-leveling cement or other methods.
1. Prepare the hole by tamping the bottom surface of the hole with a flat-ended pole such
as a pickaxe handle, then adding a few centimeters of sand to support the base of the
Trillium Compact.
Chapter 2 - Installing a Trillium Compact Posthole Seismometer
16889R10 • 2020-11-12
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