Abstract: A method and apparatus for determining the acoustic properties of the earth utilizes one or more identical, non-interacting, first spaced arrays of point sound sources and one or more identical, non-interacting, second spaced arrays of point sound sources with corresponding arrays of the first and second sources containing the same number of point sound sources in the same spatial relationship, with the spacing between the point sources of the second array or arrays being a factor .alpha. greater than the spacing between corresponding point sources of the first array or arrays. The energy of the radiation emitted by each point source of the first array(s) is greater than that emitted by the corresponding point sources in the second array(s) by a factor of .alpha..sup.3.

Abstract: A hydraulically-powered yo-yo reel for handling a marine seismic cable in shallow water. At the beginning of a recording episode, a partially reeled-in seismic cable is released to drift to a standstill behind a ship. Data are recorded. The cable is then accelerated to match the ships's velocity. Following the initial acceleration, the cable is superaccelerated as it is partially reeled in. A microprocessor adjusts a dwell time between recording episodes to compensate for small variations in the ship's velocity.

Abstract: An apparatus to remotely control the depth in the water of a marine cable, such as a streamer of seismic geophones or hydrophones towed behind an exploration boat during seismic surveys of submerged formations, and maintain the cable at a desired depth. The depth at which the cable is maintained may be remotely adjusted for a range of selected depths. A new and improved attaching mechanism for attaching the depth control apparatus to the cable is provided.

Abstract: An apparatus to control the depth in the water of a marine cable, such as a streamer of seismic geophones or hydrophones towed behind an exploration boat during seismic surveys of submerged formations, and maintain the cable at a desired depth. The apparatus includes structure to prevent damage from obstacles in the water and other imparing of performance. The apparatus includes other structure to improve performance characteristics in operation.