GFA Borehole 3D Geophone Mod

Borehole 3D Geophone


Borehole 3D Geophone Mod. GFA 50/100 is designed for seismic borehole testing according to ASTM D7400-08 (downhole) and ASTM D4428 (crosshole). It is based on 3x high-sensitivity sensor elements (nat.freq.10 Hz – 1 vertical and 2 horizontal sensors), oriented according to a triad of orthogonal Cartesian axes XYZ. Supplied with a cleat assembly to sustain its weight at the requested depth (GFA cable is graduated in meters), this borehole geophone has a pneumatic-mechanical clamping system with lateral lever and spacer block.

Simply connect the pump to the GFA panel to operate: pumping air at a pressure of 2-3 bar, you will achieve excellent sensor coupling to the borehole wall (diameter between 50 and 110mm for use with the standard spacers). GFA is lightweight and easy to transport; the anodised aluminium casing makes it suitable for use on-site and easy to maintain. Moreover, two GFA can be connected one under the other by means of a special spacer accessory. Available in two versions: GFA-50 with 50m of cable and GFA-100 with 100m of cable.

Standard equipment includes:

  • Cable reel with probe (GFA-50 with 50m cable, GFA-100 with 100m cable)
  • Nose piece for drilling muds
  • Manual Pump
  • Cleat Assembly
  • Connecting cable for seismograph


Number of geophones3 geophones with nat.freq. 10Hz+/-5% (1 vert.+ 2 horiz.), high sensitivity (100V/m/sec +/-5%)
Cable length50m or 100m, graduation in meters, mounted on cable reel with probe support
Probe dimensionsØ51mm, length 570mm (anodised aluminium case)
Borehole diameterMin. 55mm, max. 110mm (with standard spacer block; larger diameters upon request)
Cable reel dimensions540x400x250mm
WeightGFA-50: <12kg; GFA-100: <17kg
Seismograph connectionStandard: Cannon type NK2721C (GEA24, 16SN-U-P) or Souriau (GEA3, Anteo). Other adapters available upon request


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