1. A seismic data processing method comprising employing a computer system including at least one processor to: employ a seismic scaling velocity to scale a vertical traveltime corresponding to a subsurface seismic event of a seismic trace to generate a pseudo-depth characterizing the subsurface seismic event; determine a specularity value for the subsurface seismic event according to the pseudo-depth; determine a contribution weight for a seismic trace amplitude of the subsurface seismic event according to the specularity value; and perform a time migration to generate a diffraction image according to a weighted sum of seismic trace amplitudes, the weighted sum including the seismic trace amplitude of the subsurface seismic event weighted by the contribution weight, wherein the weighted sum attenuates a contribution of specular events relative to diffraction events, wherein the diffraction image highlights diffractors in a subsurface volume characterized by the subsurface seismic event.