1. A method of seismic prospecting in which a plurality of seismic vibrating sources at a plurality of spaced source points contemporaneously radiate seismic signals into the earth, each source being responsive to an individual reference signal, the seismic signals traveling by different paths to a plurality of receivers in forming at each receiver a respective complete recorded signal comprising the steps of: a. generating a first signal of a first polarity and a first directional sweep over a first predetermined frequency range; b. generating a second signal of a second and reverse polarity to said first polarity and second directional sweep opposite said first directional sweep over a second predetermined frequency range; c. determining the common frequency of said first and second directional sweeps at a common time into their respective sweep patterns; d. introducing alternately into first one and then the other of said first and second signals a taper at which said common frequency is reduced to zero; e. recording returned portions of said first and second signals to form respective recorded signals; f. separating the respective recorded signals into respective first signals and second signals to form first recorded complete signals and second recorded complete signals; and g. inverse filtering said respective said first and second recorded signals to recover information attenuated by said tapers.