Blended land seismic data acquisition employing dispersed source arrays with variable sweep length

An array of seismic energy receivers is deployed at fixed locations across the length and width of a land surface area of interest. A land fleet composed of a number of vibratory swept frequency or vibroseis seismic energy sources is deployed at predetermined initial locations within the receiver array. The sources are arranged in groups which at their initial locations are spaced from other groups of the source fleet by an intergroup spacing distance representing a segment of the receiver array. Each of the vibratory sources in a source group is assigned within that group a designated specific length for its energy emissions and a frequency sweep band different from the other sources in the group. The sources in all groups concurrently emit energy at a succession of spaced, assigned locations as they are moved incrementally over their respective intergroup spacings. The responses of subsurface formations to the emissions from the sources are recorded as a blended seismic record by the fixed array of processors and made available for processing.