Geophone accelerometer

The Q-Seabed vibration sensor is a geophone accelerometer (GAC) that converts surface displacement into an acceleration signal. The GAC has operated successfully for many years in borehole environments. The accelerometers are fixed within the sensor unit, the orientation of which is measured by inclinometers; therefore, the gimbal mounting is eliminated and the signal fidelity is greatly improved.

The GAC offers a substantially improved response compared to a conventional geophone due to the removal of resonance and spurious frequency effects. As shown in the figure below, the response is consistent over the useful seismic band from 1.5 Hz up. The dynamic range of the accelerometers at 2-ms recording is typically 136 dB. The GAC avoids the low-frequency resonance typical of conventional geophones and, therefore, provides a more repeatable low-frequency response, which significantly increases the useful bandwidth on the low end of the spectrum. This broader bandwidth contributes to better definition in the S-wave image.