Abstract: A releasable heavy mass is provided which is capable of producing by impact with the ground a shock which can be used in seismic prospecting.This mass is characterized by the fact that it comprises very many individual heavy elements connected together in a way loose enough to allow deformation of the mass without loss of cohesion on impact, and in that its base is of considerable area relative to the surface of the whole mass and is maintained substantially plane at least after release and up to impact. The mass is, in seismic prospecting, released from a helicopter.

Abstract: The invention relates to seismic prospecting of the sub-surface.At least two adjacent focuses F and F', at least one reflecting interface H and directions such as (D.sub.1) and (D.sub.2) are selected in the sub-surface. A seismic trace, from which a portion containing the effect due to the reflecting interval is extracted, is made to correspond to each direction and to each focus. The correlation function between the two trace portions relative to two adjacent focuses and the same direction is then determined. The correlation functions obtained are finally summed for the different directions.Application to high resolution seismic prospecting.

Abstract: A device for transmitting seismic data informations from acquisition devices of a seismic streamer to a central recorder an a ship, comprises at least two outward, and at least tow inward transmission lines made up of line sections interconnected by interconnection systems including means for the reconfiguration of signals, means for detecting order signals receives at said interconnection systems and switching means, and controlled by the detection means to connect different line sections, previously tested, and to by-pass faulty sections so as to form one outward and one inward continuous transmission line in good operating condition.

Abstract: The device is adapted to sample and amplify with an optimum gain multiplexed analog signals. It comprises a chain of three interconnected amplifiers, the first of which has a gain of unity, the respective gains of the two others being selected in dependence on their output voltage as compared to a reference voltage. It also comprises three memorizing capacitors each of which is adapted to memorize the output voltage of a corresponding amplifier, and switches, actuated in accordance with the gain selection for each amplifier, to make the necessary connections for operating the chain of amplifiers with the selected gain.

Abstract: A device for the sequential transmission of information elements from a sensor arrangement receiving acoustic waves at different locations and a system for recording or processing these information elements. The device includes means for generating information signals representative of the instant of reception at one of said sensor means of a directly transmitted acoustic wave emanating from a source, in the form of at least two discrete values of a continuously varying voltage which begins to be generated at the instant of reception of the direct wave, and means for determining the instant of reception from said discrete values are provided, after their transmission to the recording or processing system by a sequential transmission of the discrete values.

Abstract: This sample-and-hold unit comprises a capacitor for memorizing voltage samples and a passive compensation circuit, for substantially duplicate said voltage memorization, and adapted to compensate for a residual voltage after a first memorization by feeding back a portion of the duplicate memorized voltage.

Abstract: The invention relates to seismic sources in which a shock wave is produced in a liquid mass by the implosion of a volume of vapor, particularly water vapor. According to the invention, the vapor to be imploded is formed inside a closed, flexible enclosure, surrounding an injection head, fitted with a vapor opening 103 capable of releasing vapor at 5 bars and 170.degree. C., controlled by an electromagnetic valve. Liquid nuclei are advantageously introduced into this vapor by means of a pipe for cold water which is under pressure and under the control of an electromagnetic valve, this water arriving in the cavity in order to exit through spray openings. These nuclei produce a vigorous drop in pressure inside the vapor, and hence an implosion and a shock wave, after which a pipe allows the condensate to be recovered. The invention is of use notably as a seismic marine source.

Abstract: The invention relates to the creation of a shock wave within a mass of water by implosion of a vapor bubble.According to the invention, a controlled quantity of liquid water under pressure and which is super-heated relative to the mass of water is released quickly, at a predetermined point of the mass of water, the water advantageously being in the lower vicinity of the left-hand part of the saturation curve (portion B-D). The water liberated in this way expands and vaporizes at least partially in the form of a single bubble, which then implodes suddenly.Application as a marine seismic source.

Abstract: The invention concerns electrical prospecting of the subsoil. According to the invention, electrical prospecting is performed with either continuous or alternating current by using a drilling tubing as at leasts one of two lineal exciter electrodes. The profile of apparent resistivity thus obtained gives a very definite indication of the presence of deep anomalies, even those situated under high resistivity layers or masks, which is frequently the case in the search for deposits. Comparing the real resistivity profile with the theoretical curve obtained from a preliminary model, the extent of the deposit can be determined. The invention applies principally to petroleum, mineral or geothermal exploration.

Abstract: In a sub-soil prospecting process a vertical magnetic field transmitter dipole and a receiver dipole are placed on the ground, away from each other. The receiver dipole is oriented to detect a radial horizontal magnetic field relative to the transmitter dipole. At low frequencies, the magnetic field detected assumes asymptotic values, and by measuring these values an apparent alternating current resistivity of the sub-soil is deduced. By varying the transmitter-receiver distance, and by simultaneously using a direct current electric prospecting process, a sub-soil model is determined which is less ambiguous than those supplied by electric or induction prospecting alone.

Abstract: A seismic exploration process consisting of the application to the surface of the soil of a plurality of vertical impacts at points separated by a vertical trench cut into the soil. The vibrations propagating in the soil as a result of said impacts are then recorded, with the longitudinal wave components being eliminated from consideration. This makes it possible to produce agitation having a strong transverse wave component.

Abstract: A device for generating acoustic waves in the earth by striking a mass, housed in a guiding tube, against a target member secured to the lower end of this tube and coupled to the earth in operating conditions, including means, such as an electromagnet, for holding said mass at the upper end of said tube and releasing it at will, and means to turn the tube upside down after each operation so as to reset the mass in position for a new operation.

Abstract: A method and apparatus for marine seismic prospecting in which a long spacing linear array of seismic detectors is spaced from a seismic source and connected to a recording apparatus on a survey ship. A short spacing linear array of seismic detectors is also spaced from the seismic source and signals thereof supplied to suitable channels of the recording apparatus in common with some of the signals from the long spacing detector array. The principal and auxiliary signals in the common channels are distinguishable as a result of relative amplitude and time separation.

Abstract: Receiver of continuous structure adapted to be laid on the ground surface or underground, for seismic prospecting on land, comprising at least one support member for geophones, made of a flexible material having an elongated central portion and two lateral portions defining therewith at least one recess, said geophones being fastened to the central portion of the support member and coupled to the earth therethrough and said lateral portions being provided with longitudinal channels housing conductor cables.