Abstract: A marine seismic system includes a streamer cable which is towed by a vessel in a body of water. The streamer cable includes a plurality of hydrophones located at predetermined positions in the streamer cable which receives vibrations resulting from a seismic event occurring in the water, and provides signals corresponding to the received vibrations. The streamer cable also includes a plurality of receivers located at predetermined position in the streamer cable. Each receiver receives acoustical signals provided by acoustical sources and provide electrical signals corresponding to the received acoustical signals. A seismic event source provides a seismic event in the water. A plurality of acoustical sources cooperating with the seismic event source also provides encoded acoustical signals into the water when the seismic event source provides a seismic event.

Abstract: One or more seismic sources impart seismic pulses into the earth in a coded sequence. The coded sequence is composed of a minimum of three cycles of a Galois sequence of order N, where N is a positive integer. The response of subsurface formations to the coded sequence is obtained and correlated with one cycle or the outgoing Galois sequence of the same order. Correlation properties of the Galois sequences provide a way to sum a large number of seismograms that are superimposed in time, improving the signal to noise ratio while keeping the field time in which the seismograms are obtained to a minimum. Using this encoding technique, responses of subsurface formations to concurrent activation of each of several sources can be obtained and separated from each other.

Abstract: A method of enhancing the signal to noise ratio of seismic data includes the steps of repeatedly obtaining, from at least one array of seismic detectors, analog signals representative of sensed vibrations or pressure waves. Each analog signal is converted to discrete digital values on a time correlation basis until a predetermined quantity of analog signals have been converted. In each time correlation, the two most positive digital values and the two most negative digital values are removed. The remaining values for each time correlation are averaged so as to provide a digital representation of the analog signals.

Abstract: A method for improving signal-to-noise ratio in seismic surveying. It involves generating a series of seismic charges at time spaced intervals but at the same location. A single record is made having a time duration sufficient to cover the maximum reflection time of interest plus the total time for the series of charges. And, thereafter, the record is processed by Fourier transform of the single record to the frequency domain and by constructing frequency domain representation of the series of time intervals plus using the latter to superimpose frequency domain representations of the seismic signals resulting from each of the seismic charges. Then the processing includes inversely transforming the superimposed frequency domain representations back to the time domain.