1. A method of processing seismic data obtained from seismic sensors, the method comprising processing incident waves and reflected waves at various points on the surface of the ground so as to determine an angle reflectivity gather, characterized by the steps according to which: for various points considered, as well as for various frequencies and various shots, a local harmonic decomposition of the incident wave and/or the reflected wave as a sum of angle components is/are computed by implementing a recurrent processing according to which a harmonic of rank n+1, n being a positive integer, is determined as a function of one or more harmonics of rank n or lower to which is applied at least one filtering which depends on at least one local parameter at a point P of a subsurface area below said various points, this local parameter being chosen from among the components of the wavevector, the frequency of the wavefield, the local velocity, the local anisotropy parameters or any combination of these various parameters, a local harmonic decomposition of the reflectivity is deduced therefrom for the various points considered and is summed frequency-wise and shot-wise, an angle gather of the reflectivity is deduced from the harmonic decomposition thus obtained after summation, wherein said summed harmonic components of the reflectivity for the various points or said obtained angle gather of the reflectivity are used to provide one or more images representing the characteristics of said subsurface area.