1. A method of processing seismic images of the subsurface, comprising the steps of: analyzing a seismic image to estimate seismic horizons in an area of the subsurface; calculating an accumulation value associated with each pixel of the seismic image by accumulation along a set of estimated seismic horizons to form a synthesized image composed of accumulation values; and transforming the synthesized image to obtain a seismic representation in which signed amplitudes are allocated to the pixels of the synthesized image.