Abstract: A method of filtering and combining seismic data, such as data from two or more seismic sources having different spectral characteristics. A plurality of seismic signals are transmitted into a subterranean earth formation and a resulting data trace for each seismic signal is recorded. A correlating signal is generated for each data trace, such that the sum of the correlations of each correlating signal with its associated trace is an approximately minimum phase signal whose frequency amplitude spectrum is the sum of the frequency amplitude spectra of the seismic signals. In a preferred embodiment, the correlating signals are generated by obtaining reference signals representing the seismic signals prior to propagation through the earth formation, concatenating these reference signals and inserting a zero-amplitude signal between each reference signal, and then performing least-squares deconvolution on the concatenated signal.