1887

Abstract

Summary

The importance of low-frequency acquisition is widely recognized as it contributes to illumination of deeper targets and estimation of quantitative properties by the use of full waveform inversion. We introduce an approach of low-frequency acquisition using half-cycle pseudorandom sweeps. The waveform is characterized by continuous half-cycle sine curves with constant frequency (carrier frequency), which polarity changes randomly. Auto-correlation of the half-cycle pseudorandom sweep is close to side-lobe free delta-function, which makes it possible to obtain broad-band seismic data. We performed a field test for a crosshole seismic survey using piezoelectric source with various carrier frequencies. Each pseudorandom sweep has the same number of “half-cycles”, and therefore, the total sweep time is shorter with increasing carrier frequency. The field results demonstrated that low frequency component is not dependent on the carrier frequency, although high frequency component increases with it. Thus, half-cycle pseudorandom with higher carrier frequency can provide broadband seismic data with shorter acquisition time, which is related to flat frequency property of the piezoelectric source. This approach should provide low-frequency data acquisition from piezoelectric or other high-frequency instruments and may be a significant contribution to low-frequency data acquisition.

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/content/papers/10.3997/2214-4609.201601603
2016-05-31
2020-03-31
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References

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