Abstract: A method for simultaneous collection of seismic data of shallow and deep targets, in which two seismic streamers are towed at different water depths (1 and 2 in FIG. 2), and only one acoustic source of seismic signals is used. The seismic data recorded by the different streamers are mixed in a subsequent processing step, seismic data being weighted before being mixed by a weight which is made dependent on the recorded two-way travel time for the respective streamers, so that data from one or several streamers located at the least water depth receive a weight which decreases with travel time, whereas data from a corresponding number of streamers of greater depths receive a weight which increases with travel time.

Abstract: In seismic surveys at sea a system for maintaining the sources of seismic energy (2) at the same level when emitting their signals includes sensors (5) provided close to the sources of energy (2) for emitting signals representing pressure conditions and/or motion transmitted to a control unit (9). These signals are compared by control unit (9) for controlling driving devices (6) for the suspension lines (3) for the sources of seismic energy (2), so that their distances from the surface of the sea may be controlled to keep all sources (2) at the same level.

Abstract: In seismic surveys in waters covered with ice, where seismic impulses are actuated under water and reflected signals are detected by a streamer cable (2) towed behind a vessel (1), in order to avoid the source of noise located outside the seismic system due to the icebreaking operation of the vessel (1) the vessel (1) is stopped during active survey and the streamer cable (3) is hauled in with a speed corresponding to the desired propulsion speed of the cable during detection. After detection the vessel again resumes ordinary operational speed and the streamer is paid out with a speed which maintains the desired advancing speed of the system.

Abstract: A fastening device for fixing seismic circular devices is designed with a rigid, split, annular clamp (4) with an open void facing the seismic device (1) for insertion of at least one shock absorbing member (7) in the void. Such a clamp (4) is provided in the region of the device which is most subjected to strain, where a concentric securing ring (8) is also mounted, about which the clamp is fitted with a shock absorbing member (7) on each side of the ring. One more such clamp is provided on the seismic device (1) in order to distribute the load. This arrangement is especially suitable for use in connection with seismic airguns which are to be fixed at predetermined mutual distances in a frame structure (2).

Abstract: An encoded seismic source, such as a marine vibrator, and a receiver, such as a seismic streamer, are pulled through water at constant velocity and depth. The source is periodically actuated and the reflected acoustic signals are converted by the receiver into seismic data. The seismic data are transformed to a fixed reference frame relative to earth before being processed.

Abstract: A method in real time control systems for seismic interference to indicate an acceptable level of interference in relation to the amplitude, angle of incidence, and frequency of a seismic reflection signal, and to remove such interference loaded signals during seismic surveys, comprises steps to determine lower threshold values of coverage, identify interference and amplitude anomaly in the recorded signal of reflection, estimate the expected value of amplitude characteristic of the signal on the basis of recorded amplitude characteristics of recorded signals from one or a plurality of preceding series of survey, mark time windows in which interference and/or amplitude anomaly are identified, generate a table of the number of times a certain time window was marked in the series of recordings of the same point of reflection, assign limits on the number of interference events to various marked time windows, and remove from the recordings those time windows wherein the number of interference events exceeds the l

Abstract: A method for determining the position of at least two seismic streamers (S.sub.1, S.sub.2) in a reflection seismic measuring system, wherein hydroacoustic distance measurements are used which are taken by means of acoustic transceivers provided in vessels (1), buoys (8), floats (5), seismic sources (2) and in the seismic streamers (S.sub.1, S.sub.2). Absolute reference positions are determined by position determining equipment provided in at least two locations, for instance, on a vessel (1) or a float (5). The acoustic transceivers and the position determining equipment form a three-dimensional structure. The position determination takes place by trilateration between the acoustic transceivers and the determination of at least two reference positions so that there is no dependency on compass bearings or optical visibility, and high redundancy is obtained. The method is particularly suited for application in connection with three-dimensional marine seismic surveys.

Abstract: An exterior mirror for a motor vehicle has a base member adapted to be mounted on a vehicle body, a housing containing a reflective member and having an end face to confront the base member with a peripheral edge serving as an abutment edge which engages the base member for relative pivotal movement. A link is pivotally connected at one end to the base member and a tension spring is connected between the link and an attachment point in the interior of the housing to urge the abutment edge on the housing into abutment with the base member. The end of the link opposite to the end connected to the base member is pivotally connected to the housing and the spring is connected to an intermediate point on the link. The base member and housing are shaped to conceal the abutment edge of the housing when said peripheral edge is in engagement with the base member around its entire periphery.

Abstract: Methods for interpolation of severely aliased events in which composite wavelets of a section of seismic data traces are separated by wave field decomposition into their component wavelets. The spatially aliased component wavelets are identified to form a first class of wavelets. A second class of wavelets is comprised of non-aliased component wavelets. The wavelets in the second class or non-aliased component wavelets are interpolated in accordance with known techniques, such for example, as sinc interpolation whereas the spatially aliased component wavelets are interpolated in accordance with dip guided interpolation to provide the same number of traces as those comprising the second class of wavelets. The interpolated first and second class of wavelets are summed to provide a section of seismic data substantially free of spatial aliasing.

Abstract: The device comprises a manipulator (148) whose body (149) houses deformable positioning transmitter bags (145 to 147) each connected by a corresponding hydraulic circuit to a positioning receiver comprising a deformable bag (130 to 132, 133 to 135), whose increases in volume in response to the compression exerted by the user on at least one of the positioning transmitter bags (145 to 147 control a change of the positioning of at least one controlled member. The device may contain a connector connecting the transmitter bags to the receiver bags, and also path switching hydraulic circuits permitting the selective control of one of two different members by a single manipulator. Application in particular to the control of external rear view mirrors on vehicles.

Abstract: A remotely controlled rear view mirror assembly for a motor vehicle consists of a base adapted to be mounted on a vehicle body, a casing mouonted on the base and a reflective member mounted in the casing for angular movement about two mutually perpendicular axes. A control member is mounted on the base so as to engage with three elongate members each of which has two end portions of cross section adapted to resist bending about first and second mutually perpendicular transverse directions, interconnected by an intermediate portion having a cross-section adapted to permit bending in the first transverse direction. Guide means mounted in the casing are arranged to direct one end of each elongate member into abutment with a surface of the reflective member facing the interior of the casing, and to direct the other end of each elongate member through an opening in the casing facing the base so as to abut against the control member.

Abstract: In order to avoid noise and error-sources a marine streamer (3) for use in seismic exploration is provided with a buoyancy member (8) which is snake-shaped or tubular-shaped and slightly flexible and supports the active member (9) of the streamer by the aid of narrow suspension ropes (10). The streamer may be made adjustable as regards its height and it may be dividable into sections.

Abstract: In order to accumulate data from which the signature of an array of n interacting seismic sources 21 to 27, for instance marine seismic sources in the form of air guns, can be determined, the array is actuated and the emitted pressure wave is measured at n independent points whose positions will respect to the array are known by hydrophones 31 to 37. Data from the measured pressure wave is stored for subsequent processing to produce n equivalent signatures of the n sources taking into account the interactions therebetween. The signature of the array is then determined merely by superposing the n equivalent signatures.

Abstract: A cable handling apparatus draws in a cable, such as a seismic streamer, along a generally linear path and feeds the cable to a winch which winds in the cable from the apparatus under constant tension.

Abstract: An arrangement for deployment and towing of a plurality of seismic cables (2) in parallel and at a mutual distance behind a vessel whereby seismic cables (2) are wound on winch barrels (4), and are provided with an inner cable member (3) which forms a connection with the vessel (1) during a towing operations, and is, additionally, provided with a paravane/control (14, 15) to guide and maintain the cable (2) laterally in relation to the towing vessel (1). Reliable and simple depolyment and towing of the seismic cables (2) at a large distance laterally in relation to the center line of the vessel is achieved by running the inner cable member (3) through at least one guide pulley (5) suspended from a line (7) that is adjustable in length from the vessel, and is, preferably extended over a derrick device (9) projecting from the vessel. Guide pulley (5) can be hauled in and paid out from the vessel, at the same time as inner cable member (3) can be let out to a greater length from the vessel.

Abstract: An angular member provided on seismic cables towed by a vessel and laterally displaced in parallel and in relation to the course of the vessel comprises a frame at least partly enclosing the cable in the area of angular deflection between an inner cable portion extending obliquely to the towing direction and the active main cable portion. The frame is formed of two frame plates secured in spaced relationship and having at the lead-in end for the cable a cable-fastening device and at the other end a pivotable ramp swingable in the plane of the frame plates. The ramp has a further fastening device for the cable. Another fastening device is pivotably connected to the frame plates for connecting thereto a wire to a paravane or the like. When towed in the water the angular member absorbs most of the forces normally exerted on the cable at the area of angular deflection.

Abstract: A device for controlling a seismic cable that is towed behind a vessel (1), so that the cable follows a path that is displaced laterally in relation to the path of the vessel, comprises a frame structure (6, 7) extending transversely to the towing direction and outwardly from the area of gun suspension from the cable having longitudinal frame members provided with intermediate transverse members extending obliquely or in a curved manner whereby the front ends of the transverse members, as seen in the towing direction, are disposed further outwards laterally than the rear ends of the transverse members. When towed, the frame will this be forced outwardly by the water flowing through the frame structure and the desired lateral displacement will be achieved.

Abstract: A reinforcing device to achieve stable fastening points for the inner portion (2) of seismic cables, especially cables that are towed laterally displaced in parallel in relation to the towing vessel and provided with at least two layers of armoring (5,6) intended for absorbing stretch loads on said cable, comprises a fastening means on at least one of the end areas of the inner portion (2), and gripping surfaces for external equipment and shaped with at least two securing chambers (3,4). For assembling the outermost layers of armoring (5,6) of said cable are separated and inserted into one chamber each (3, 4), wherein they are secured to form an integrated connection with said casing (2).

Abstract: An arrangement for spacing a floating body from a mother vessel during borehole-seismic measurements, wherein the floating body includes at least two buoyant bodies connected by a rigid framework and which supports the seismic equipment, the floating body is maintained in a correct position for transmitting seismic pulses by a crane or boom mounted on the mother vessel, a tube or hose system is mounted on the framework for ejecting a pressurized medium, preferably water, against the side of the vessel through nozzles, and the pressurized medium is transferred to the system through a hose coupled to a source of pressurized fluid on board the vessel.

Abstract: A device for use in borehole-seismic measurements at sea whereby seismic energy sources (7) are suspended below the surface (D) and connected to a handling line (2) which is operated by a crane arrangement on a vessel. By suspension of a minimum of two seismic energy sources (7) from a stand (3) at a distance from mutually separated floats (1) rotatably connected on horizontal axes (9) to the stand, seismic energy sources (7) can be placed and maintained at a constant depth below the surface, whereby several seismic sources (7) can be used simultaneously. The stand (3) is equipped in its central area with a guide (4) for the handling line (2), which is divided at the end connected to the respective energy sources' (7) suspension lines (8), which simplifies the positioning of the device.