Sensor Placement
A seismic station should measure motion of the ground or structure of interest while minimizing unrelated vibration. The correct site depends on the instrument and monitoring objective.
Select a stable site
Prefer a location with:
- Rigid coupling to a concrete slab, foundation, bedrock, or purpose-built pier
- Low vibration from machinery, traffic, doors, and footfall
- Stable temperature and protection appropriate to the enclosure
- Reliable power and communications
- Safe access for inspection and maintenance
- Low risk of flooding, tampering, cable damage, or antenna obstruction
Ground-floor or basement installations are normally more representative of ground motion than upper floors. An upper-floor sensor can be useful for structural response, but its waveform includes the building's motion and must be documented accordingly.
Investigate noise rather than using fixed distances
Vibration sources vary too much for one universal separation distance. A small pump rigidly connected to the same slab can matter more than a larger machine farther away, and road or rail noise depends on ground conditions and traffic.
Survey the proposed site while likely noise sources are active. Consider:
- HVAC equipment, pumps, generators, compressors, and elevators
- Vehicles, railways, construction, and pedestrian traffic
- Wind acting on an enclosure, pole, antenna, or loose cable
- Water flow, rain impact, and vegetation
- Electrical equipment and poor power supplies
If possible, compare candidate sites using waveform or noise-spectrum measurements before permanent installation.
Mount rigidly
- Clean loose material from the mounting surface.
- Use mounting hardware suitable for the substrate.
- Prevent rocking, sliding, and rotation.
- Keep cable tension and movement from transferring force to the sensor.
- Avoid carpet, foam, raised-floor panels, and flexible poles unless the monitoring objective specifically requires them.
- Recheck fasteners and leveling after installation.
For outdoor equipment, use a stable pad or pier and an enclosure installation approved for local weather, drainage, and security conditions.
Orient and level the instrument
Follow the reference surface and axis marks for the exact sensor and enclosure.
- A vertical geophone must remain upright and level within its specified tolerance.
- Horizontal accelerometer axes should use a recorded orientation.
- If axes are not aligned to geographic north/east, record the actual azimuth so data can be interpreted or rotated correctly.
- Do not infer orientation from a connector because board and enclosure layouts can change.
Record station metadata
At installation, record:
- Device ID and station code
- Coordinates and elevation
- Sensor and enclosure revision
- Mounting surface and method
- Axis orientation and level
- Floor or structural location
- Power and communications arrangement
- Nearby noise sources
- Installation date and photographs
Update this record whenever equipment or site conditions change.
Verify after installation
A station is not accepted merely because it appears Online. Confirm:
- Current telemetry reaches the intended system.
- Timing and station metadata are correct.
- Waveforms are continuous and plausible.
- Background noise is suitable for the monitoring objective.
- Known local activity is recognizable and does not saturate the channel.
- The enclosure, cables, antennas, and mount are secure.