For seismic observations in mines or wells, instead of three-component geophones, four-component ones with sensors located along the tetrahedral axes are sometimes used. When a geophone is placed in a hard-to-reach area for a long time, the requirements on its reliability increase, so it is necessary to monitor its operation. From this viewpoint, a four-component geophone has certain advantages over the conventional three-component geophone, the three ones being suppression of instrument noise for the recalculation of a four-component record into a three-component one, saving of the polarization analysis data in case one geophone component fails, and sensitivity control of individual geophone components. To suppress instrument noise in records from a four-component geophone, the following processing should be performed: first, calculation of the covariance matrix of recording components, second calculation of the eigenvalues and eigenvectors of the covariance matrix, and third, the parameter used to assess the ratio of instrument noise to the useful signal is calculated. After that, the operator projecting a four-component displacement vector onto a three-dimensional subspace is constructed.
