1. A method to generate an image of a subterranean formation, the method comprising: receiving a gather of receiver seismic data generated by receivers of a seismic data acquisition system; smoothing amplitudes of each trace of the gather of receiver seismic data to generate a smoothed-amplitude gather, the smoothed-amplitude gather having smoothed-amplitude traces, each smoothed-amplitude trace corresponding to a trace of the gather of receiver seismic data; stacking the traces of the gather of receiver seismic data to generate a noise-reduced trace, wherein each amplitude of the noise-reduced trace is calculated as a sum of amplitudes of the traces of the gather of receiver seismic data weighted by smoothed amplitudes of corresponding smoothed-amplitude traces of the smoothed-amplitude gather; and generating an image of the subterranean formation based at least in part on the noise-reduced traces, the image revealing subsurface structural information about the subterranean formation.