A method for determining an optimum spacing of seismic energy sources based on mutual admittance includes deploying a plurality of seismic energy sources along a source line, separated by a selected spacing. Seismic receivers are deployed along a receiver line orthogonal to the source line. Seismic energy is simultaneously transmitted from each of the plurality of seismic energy sources while recording signals from the seismic receivers. The transmitting and recording of signals is repeated for a plurality of different spacings between the energy sources. Seismic energy in the recorded signals is determined in separate time windows selected to represent reflected body wave signal, and source generated ground roll noise, respectively. A signal-to-noise ratio with respect to the spacing of the seismic energy sources is calculated and the optimum spacing between energy sources is selected based on the signal-to-noise ratio.