1. A method for processing, on a computer, seismic data carrying information about subsurface, the method comprising: receiving the seismic data recorded by detectors arranged on receiver lines; splitting the seismic data into groups, each group including subsets of seismic data for which a distance from a shot point where a seismic wave is generated to a receiver line is within a predetermined range for the group; extracting signal data by subtracting noise from the seismic data for each group of seismic data, wherein the extracting includes generating a block Hankel matrix using a Fourier transform of the seismic data pertaining to the group, performing a Singular Value Decomposition (SVD) of the block Hankel matrix, and estimating the noise assuming that coherent noise corresponds to largest singular values; and outputting the signal data useable to generate an image of the subsurface, wherein the extracting of the signal data for each group further includes performing dip filtering to further separate signal leaked in the estimated noise, and enhancing the dip-filtered estimated noise based on a least square matching filter with the seismic data, the enhanced dip-filtered estimated noise being then used to extract the signal data.