Guralp Systems CMG-3T - Manual (Page 14)

CMG-3T
11.Ensure that the sensor cable is loose and that it exits the
seismometer enclosure at the base of the instrument. This will
prevent vibrations from being inadvertently transmitted along
the cable.
2.4 Installing in pits
For outdoor installations, high-quality results can be obtained by
constructing a seismic pit.
Depending on the time and resources available, this type of
installation can suit all kinds of deployment, from rapid temporary
installations to medium-term telemetered stations.
Ideally, the sensor should rest directly on the bedrock for maximum
coupling to surface movements. However, if bedrock cannot be
reached, good results can be obtained by placing the sensor on a
granite pier on a bed of dry sand.
1. Prepare a hole of 60 – 90 cm depth to compacted subsoil, or
down to the bedrock if possible.
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