Abstract: Seismic exploration on land and on ocean beds is performed by emitting vibrational acoustic signals of long time-duration within a desired frequency spectrum at one or a number of points, the signals corresponding to the waves received from the reflectors being then processed. The method further consists in forming the complex spectrum of the received signal corresponding to the emitted signal in respect of each frequency band, in forming the complex spectrum of a reference of the emitted signal in respect of each frequency band and in dividing the complex spectrum of the received signal by the complex spectrum of the reference of the emitted signal, at least an external portion of each complex spectrum being eliminated in the case of each complex spectrum.

Abstract: A system for determining the location of a seismic wave source in a homogeneous medium (the soil) comprises a linear array of equispaced sensors sampled by respective pulse extractors in turn feeding a plurality of cascaded two-dimensional recursive digital filters which act as phase shifters estimating in small or incremental steps the magnitude of the wave field away from the sensor array. The output signals of the sensors are sampled at a rate equal to the ratio of the distance between the sensors and the wave velocity in the homogeneous medium, thereby giving rise to samples distributed in a single quadrant of the space-time domain. An attenuator connected in series with the phase-shifting filters damps frequency components outside the rotated quadrant, while an equalizer connected in cascade with the attenuator ensures a global linear response thereof.

Abstract: A multi-purpose seismic transducer includes a first seismic sensor having a first transfer function. A transfer-function shaping filter is coupled to the output of the first seismic sensor. The filter is adjustable to shape the first transfer function to match a plurality of different second transfer functions.

Abstract: A method and apparatus for reducing ground current interference with electrical signals representative of seismic signals, said electrical signals passing from at least one geophone to a recording system via an electric circuit including a balancing circuit coupled to ground, whereby a bridge circuit is formed which includes the geophone, the electric circuit and at least part of the recording system, and wherein the balancing circuit comprises two pairs of arms, each pair having at least one arm with variable impedance. Automatic adjustment of the variable impedance occurs based upon electrical information received by a detecting circuit for determining the variation in unbalance of the bridge circuit. Impedance adjustments may be made stepwise or continuously in alternative embodiments of the invention.

Abstract: Common depth point seismic signals from a plurality of seismic receivers are recorded on a field recorder. A first time shifter corrects the seismic signals for multiple normal moveout. A linear dip filter rejects unwanted multiple reflection signals. A second time shifter reverses the multiple normal moveout correction of the first time shifter. A third time shifter corrects the primary reflection signals for normal moveout. The primary reflection signal are then stacked and recorded as a composite common depth point seismic signal.

Abstract: An illustrative embodiment of the present invention includes methods for Seismic Data Processing which may be used to enhance the signal/noise ratio of seismic signals taken by use of the Common Depth Point or Hundred Percent Coverage survey techniques. The methods preserve time alignment and amplitude of the signals while effectively removing the noise therefrom. Small portions of the record centered at a selected time on a selected trace are processed to extract the coherent signal component from the reference trace as determined by comparison with other spacewise adjacent traces. Output records comprising the enhanced signal data and the noise data are produced.

Abstract: A method of enhancing a "gather" formed of a plurality of unmoved out common depth point (CDP) data traces. The gather is formed of a plurality of seismic traces arranged in a display in which time varies along the horizontal axis and distance between source and detector (range) varies along the vertical axis. The gather is incrementally processed by cross correlating trace segments within a defined area or search window. To this end, the center trace within the window is selected as a reference trace which is multiplied by a taper function and cross correlated with the other traces in the window to provide a coherent trace and a separate noise trace, both of which are produced in the output. The window is shifted on the gather and the procedure is repeated until every trace has been processed. In the cross correlation technique, the trace segments in the window are examined along a derived hyperbolic curve.