GB1516866A - Method of operating vibrators to produce seismic signals - Google Patents

Abstract

1516866 Seismic signal generation; autocorrelation DEUTSCHE TEXACO A G 10 Nov 1975 [12 Nov 1974] 46419/75 Heading G1G A method for operating vibrators for generating seismic signals within a specified frequency range found suitable for an exploration target by means of a sinusoidal control signal, said control signal being determined in an automatic computing system, comprises the following steps: determining a reference autocorrelation function with low side lobes and frequencies within the specified frequency range, determining the amplitude spectrum of the reference autocorrelation function, determining the amplitude spectrum of the seismic signal as the square root of the amplitude spectrum of the reference autocorrelation function, determining the amplitude spectrum of the control signal of the vibrators from the amplitude spectrum of the seismic signal by means of the relation between control signal and seismic signal, and determining the variation with time of the frequency of the sinusoidal control signal from the amplitude spectrum of the control signal. The "Amplitude Spectrum" is the modulus of the generally complex frequency spectrum. Only for symmetrical functions, such as the autocorrelation function, is the frequency spectrum real and is thus, possibly apart from the sign, equal to the amplitude spectrum. An autocorrelation function comprising desired low secondary lobes may be provided with the aid of linear filters as employed in filter technology for smoothing oscillating signals.