Abstract: The invention relates to a marine seismic source which emits an FM signal linearly increasing from 10 Hz to about 100 Hz. The source has a number of transducers which are flexible sleeves containing a pulsing hydraulic fluid.

Abstract: In seismic exploration of water-covered areas of the earth, a seismic cable containing seismic energy detecting means spaced along the cable is used. The detecting means are grouped into one or more arrays situated along the length of the cable, and each array is divided into a plurality of groups. The detector outputs within each group are connected in parallel within the cable. Selected group outputs, corresponding to varying segmental lengths along the cable, are summed to enhance seismic data signal-to-noise ratio. The summed signal used for seismic analysis is determined by the maximum array segmental length over which reflected seismic signal components are substantially phase correlated. This length varies with record time, with geologic dip of the earth layers, and with distance of the detectors from the seismic source. This invention permits the selection, during seismic analysis, of the array segmental length that provides the most useful seismic data.