Orientation of a downhole triaxial geophone

The bearing and elevation of a geophone's axes are unknown when a geophone package is placed in a deep exploration borehole. Auxiliary instruments may be incorporated into the downhole package to give some indication of local attitude relative to some external reference field. An alternate approach to determining the orientation of a remote tool is to compare its triaxial response to that expected for a known elastic wavefield. The accuracy of the measurement depends on the quality of the geophone-to-formation coupling and on the extent of one's knowledge of the externally impressed wavefield. -from Authors