Described are methods for obtaining seismic signals representative of properties of the earth's interior, including the steps of obtaining near-field acoustic signals recorded in the vicinity of a seismic source (13), muting from the near-field acoustic signals at least partly signals representing direct arrivals from the seismic source (13), and using a remaining part of the obtained signals as estimate of a zero-offset data set. The zero-off set data set can then be used to interpolate data from conventional acquisition location, such as streamers (11), to locations closer to the source (13).