The seismographs for “active seismic” surveys these are instruments capable of measuring the seismic perturbations produced artificially in the ground by a sledge hammer or an explosive charge and measured by a type of sensor known as a geophone.
Model 16S12-P-12 Channels
A certain number of geophones (min. 3, more often 12, 24 or more) are driven into the ground, arranged along a rectilinear profile (seismic spreading) with a certain spacing (e.g. 12 geophones at 10m spacing covering a profile that is 110 m long).