Abstract: A method for improving seismic sections includes generating seismic signals at source stations, recording seismic traces at receiver stations and gathering the seismic traces as a first gather at a common point as a function of the offsets between the source stations and the receiver stations. A common point (MMOCMP) is selected, a half-offset between source and receiver stations is redefined as a function of the distance between the selected common point MMOCMP and the RAWCMP, and the seismic traces are sorted as a function of the redefined half-offset, constituting a second gather of traces. The method permits one to obtain true located subsurface information at any desired point for velocity analysis.

Abstract: A method for monitoring an area of the surface of the earth uses measurement probes arranged in a grid for determining the self-potential with respect to a base probe. The measurement probes are interrogated repeatedly. The earth resistance between measurement probes and the base probe is also measured repeatedly between measurements of self-potential. Potentials on the surface of an area of the earth can be determined precisely, independently of earth-resistance changes.

Abstract: The invention relates to a marine-seismic streamer having a liquid-filled tube (4) in which there are arranged, in the longitudinal direction, hauling cables and flow-obstructing devices including shaped pieces (2) which are spaced apart in the longitudinal direction for dividing the streamer into sections, and hydrophones (5). The shaped pieces (2) are of cylindrical construction with an outside diameter smaller than the inside diameter of the tube (4) such that an annular gap (9) is formed between the tube (4) and each shaped piece (2). The shaped pieces (2) have at least one annular seal (10), the outer diameter of the annular seal (10) corresponding to the inside diameter of the tube (4).

Abstract: A vibrator for producing seismic vibrations in the earth is carried by a vehicle. The vibrator has a base plate, a reaction mass and support plates and a lifting and lowering apparatus for raising and lowering the vibrator between a raised transportation position and a lowered operating position in which the base plate is pressed against the ground. The lifting and lowering apparatus includes piston and cylinder units each connected at one end to the vehicle chassis and at the other to a support plate. In one embodiment, the piston and cylinder units are attached to the vehicle by belt-type pivotable bearings to permit swiveling of the vibrator so that the base plate is tiltable to adapt to an uneven earth surface. In another embodiment, the piston and cylinder units are attached to the vibrator by spherical pendulum support bearings which also allow swiveling and tilting of the base plate.

Abstract: A hydrophone for a marine seismic streamer has a pressure sensor with outer membrane surfaces on which piezoelectric sensors (4, 5) are secured. The pressure sensor is formed from two spaced steel disks (1, 2) having recesses directed toward one another and which are laser-welded at the edges in a gas-tight manner. The pressure sensor is electrically insulated from its external environment by a synthetic resin coating, which may enclose the entire pressure sensor, including the connecting wires. A method of making the hydrophone is also disclosed. The hydrophone can be manufactured so as to be small in dimensions and weight, is mechanically sturdy and capable of withstanding overload, as well as being protected by the synthetic resin coating against short circuiting and corrosion.

Abstract: Two or a larger even number of compressional wave producing vibrators are symmetrically disposed in two groups on opposite sides of a profile line in closely spaced relationship. The vibrators are energized by the same (or identical) sweep signals, the signals to one vibrator (or group) on one side of the line being separated in phase by 180.degree. from the signals to the vibrator or group on the other side. P-wave components are thereby cancelled, leaving the shear waves to be propagated.

Abstract: A method for determining the location of a combustion front during subsurface combustion and gasification in a coal seam and of a change of electrical properties of the coal includes emitting radar signals from an elongated antenna. The antenna is located in a borehole within the coal seam. The radar signals are received and recorded for a determination of their travel time and amplitude.

Abstract: An improved seismic measuring cable includes a series of hose sections containing hydrophones or the like joined together by coupling devices having cylindrical sections carrying sleeves joined to the hoses and half-tube portions joinable to each other. Each half-tube portion has castellations which interlock with a like half-tube portion to form a tension-resisting cylindrical closed volume for containing electrical connectors to interconnect wires leading to the hydrophones, the interlocked half-tubes being then covered by a cylindrical jacket. Tension load cables extend between the coupling devices at opposite ends of a hose section. The hoses can be oil filled. Embodiments of hose supporting members, hydrophone supports and joining means are disclosed.

Abstract: A mobile seismic energy source is formed by an automotive vehicle equipped with a vibrator type seismic energy source, a lifting mechanism, means for generating fluid pressure, and control means. Frame means pivotably linked to the vehicle chassis are provided for supporting the vibrator which is lowered into operational position and raised therefrom by the lifting mechanism acting between the vehicle chassis and linking arms of the frame means.