Characteristic analysis and data comparative of linear and nonlinear low frequency sweep in vibroseis

Abstract

Low-frequency seismic data plays a crucial role in seismic data processing and seismic wave inversion. At present, there are two methods to realize the low-frequency excitation of vibrators: one is that the low-frequency vibrators are excited by linear sweep signals, and the other is that the conventional vibrators are excited by nonlinear low-frequency sweep signals. The cost of exploration using low-frequency vibroseis is high, and it is challenging to obtain sufficient low-frequency information using traditional vibrators. To this end, this paper comparatively studies the low-frequency sweep signal characteristics and data effects of low-frequency vibrator and traditional vibrator. Therefore, three kinds of linear and nonlinear low-frequency sweep signals are designed. Theoretical analysis shows that there are certain differences between linear and nonlinear in design methods, signal shapes, etc., but after correlation calculation, the signal spectrums reflecting the seismic response and the related wavelet shapes are basically consistent. Besides, the actual force signal data shows that the linear and nonlinear harmonic distortion are basically equivalent. Finally, based on the forward simulation of three sweep signals and the comparative analysis of field test data, it can be considered that the linear and nonlinear low-frequency sweep signals of vibrator have almost the same denoising ability under the basic conditions of spectrum and wavelet. Both can achieve low-frequency excitation and obtain rich low-frequency information, and the quality of seismic data is basically the same, so they can be applied in practical production.