Method for determining horizontal geophone orientation in ocean bottom cables

A method for determining azimuth of an in-line horizontal geophone within a seismic receiver at a known location on an ocean bottom, comprising the steps of:

• measuring during a selected time interval first-break signals produced by the in-line horizontal geophone and a second horizontal geophone perpendicular thereto, the signals being from a compressional wave originating at a source, the source being at a known azimuth ψ with respect to the receiver;
• resolving the first-break signal into components along a line from the source to the receiver and a line perpendicular to the line from the source to the receiver by mathematical rotation of the signals through an angle θ;
• calculating energy of the first-break signal along the line perpendicular to the line from the source to the receiver for different values of θ to determine θm, the value of θ for which the energy along the line perpendicular to the line from the source to the receiver has a minimum value;
• calculating the difference of ψ and θm to determine azimuth of the in-line geophone;
• during the selected time interval measuring a pressure signal from a hydrophone, the hydrophone being in proximity to the in-line horizontal geophone;
• cross-correlating the pressure signal from the hydrophone with the signal from the in-line horizontal geophone in the direction of θm and in a direction 180 degrees therefrom;
• and
• selecting the direction that yields negative cross-correlation to confirm the orientation of the in-line horizontal geophone.