Abstract: Hydrophones are installed in each tank of a liquid cargo tanker ship. In the unfortunate event that the tanker collides with an obstacle in the water, the hydrophones detect the shock wave due to the collision. The relative first arrival times of the shock wave at the respective hydrophones are measured and the arrival-time differences between two hydrophones of any two different selected pairs of hydrophones is calculated. Hyperbolic lines of constant time difference are projected on a map of the locations of the hydrophones on the ship. The intersection of the lines of position representing the calculated first arrival time differences marks the location of the impact of the ship with the obstacle.

Abstract: A ruggedized depth transducer for measuring ambient hydrostatic pressure adjacent an acoustic source wherein the transducer includes a housing having a depth sensor mounted therein. The housing further includes a bore for placing the depth sensor in fluid communication with the ambient pressure. Mounted within the housing bore are a series of mechanical filters for attenuating high-intensity pressure spikes generated by the acoustic source from damaging the depth sensor contained within the housing. The mechanical filters allow gradual changes in ambient pressure to pass into the bore and influence the depth sensor.

Abstract: A system for maintaining a substantially constant tension on a towed seismic cable, wherein the instantaneous towing force and the instantaneous cable displacement relative to a fixed shipboard reference are continuously measured and sampled. A microprocessor associated with a servo controlled capstan device, uses those measurements to pay out cable or to retrieve cable in response to an increase or decrease in the instantaneous towing force. The microprocessor also tries to minimize the average cable displacement.

Abstract: A method for optimizing the acoustic signal-to-noise ratio during a useful maximal-length recording cycle within the time frame of a minimal-length recording episode. To implement the method, during an intermittent-tow seismic operation, the noise level due to cable manipulation during an entire recording episode is monitored. A quiet-window of a desired length is established by adjusting the length of the interval during which the seismic cable is at rest. The initiation of a recording cycle is adjusted relative to the quiet window to take maximum advantage of the quiet period.

Abstract: Selected sections of a seismic streamer cable are provided with an acoustically-triggered compressed gas supply. The acoustic triggering devices associated with each compressed gas supply may be individually addressed by a coded signal. In the event that the streamer cable is severed, the gas supplies of the severed sections of the streamer are used to inflate the jackets of those severed sections so that they will float to the water surface for salvage.

Abstract: A pulse is applied sequentially to each geophone input line to the stator of a CDP switch. A pulse detector is connected to the first output line of the CDP Switch cursor. A counter counts the number of pulses applied to inactive input lines before a pulse is detected by the pulse detector. The pulse count is the geophone group number of the first active geophone group.

Abstract: A seismic streamer cable, composed of a plurality of cable sections includes a common transmission line and an internally mounted inductive element in each section. The inductive elements are coupled in parallel to the common transmission line. A plurality of depth transducers, each associated with an inductive pickup, are secured externally to the streamer cable at desired intervals, adjacent to one of the internal inductive elements. A control signal is periodically transmitted through the transmission line and is received, by inductive coupling, at each transducer after a selected delay. In response to the delayed control signal, the transducers inductively launch a depth-proportional signal into the transmission line for reception by a depth readout device.

Abstract: A towing link consists of spaced-apart head and tailpieces. The headpiece includes a towing eye and a pair of lugs for receiving the stress members of a streamer and a lead-in cable. The tailpiece defines a pair of bores through which the stress member and electrical conductors of the two cables are inserted and sealed. A pair of mating connector plugs are provided to interconnect corresponding conductors of the two cables. The assembly is enclosed in a watertight plastic boot.

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: The resistive sensor consists of a pair of electrodes separated by an impervious insulating material. The sensor is mounted adjacent to an exhaust port of an airgun, in the path of the air blast that results when the gun is fired. When the air gun is submerged and not activated, the surrounding water creates a low-resistance path between the electrodes. When the gun is fired, the air blast blows the water away from the electrodes and the resistance between them abruptly increases substantially. A bridge circuit detects the instant of resistance change and generates an electrical transient to mark the time that the gun fired.

Abstract: In a multichannel seismic system, channel-sequential seismic data samples gathered during a first recording cycle are demultiplexed to sample-sequential format in a core memory. The core memory is divided into pages each of which is addressable in two dimensions by rows and columns as a rectangular matrix. The channel-sequential data samples are serially loaded into the respective pages in channel-sequential order by columns. At the end of the first recording cycle, the data are extracted from the respective pages by rows in sample-sequential order. As the data samples from the first recording cycle are being extracted by rows, data samples from a second recording cycle are loaded serially by rows into the respective pages that were vacated by the extracted data samples of the first recording cycle.

Abstract: The apparatus provides a means for time-varying the signal sample rate and the subsurface coverage during a single seismic reflection recording cycle. A number of seismic sensor arrays are connected to a multichannel seismic recording apparatus through a data-signal transmission means such as a multiconductor cable or a telemetric link. Each seismic sensor array is, of course, connected to a corresponding input channel, including a preamplifier, in the multichannel recording apparatus. Included in the recording apparatus is a set of addressable multiplexer switches. The multiplexer switches (or for simplicity, simply multiplexers) are divided into at least two groups. Separate sets of anti-aliasing filters, each set having a different pass band, are connected to the input terminals of the respective subgroups of multiplexers. One half of the input channels are connected to both sets of filters; all of the input channels are connected to one set of filters and multiplexers.

Abstract: A connector assembly such that when a first half of the connector receives a second half, a vent hole is defined therethrough. With the second half disconnected and a third half coupled to the first half, the vent hole is sealed.