A system is disclosed for processing a group of spatially related seismic data traces in which seismic data windows extending over selected portions of said group of spatially related seismic data traces are defined, and a transform is applied to the successively selected windows to convert the seismic data within the successively selected widows to the frequency domain thereby generating a frequency spectrum of the seismic data within said successively selected windows. Selected frequency spectra are then combined to generate an average of the selected frequency spectra, thereby generating averaged frequency spectra, ane the averaged frequency spectra are utilized to generate data related to the location of thin beds in the earth's subsurface.