Intra-water reflections on multichannel seismic data

About 3800 km of multichannel deep seismic reflection data were collected in 1991, during the PHEDRE cruise, in the Central Indian Ocean. The main objective of this cruise was to study distributed compressive deformation of the oceanic lithosphere along the India-Australia diffuse plate boundary. The signal was generated by an array of 8 Bolt airguns of a total volume of 4271 cubic inches, and received on a 96 channel streamer, 2.4 km long. 36 seconds of signal were recorded at a 4 ms sampling rate; the shot interval was about 100 m (40 s). The purpose of such a long recording window was the application of statistical deconvolution methods based on the analysis of several multiples. The amount of magnetic tape saved by the application of a delay was considered negligible in regard to this exceptional record length, and therefore no delay was used during the whole cruise.