The Application Of Time-frequency Analysis In-Shallow Seismic Exploration

This paper introduced the basic concepts and the mathematical expressions of time-frequency analysis, the relationships between a number of linear time-frequency analysis and their merits and demerits.Under the guidance of time-frequency analysis theory, Wavelet transform to improve the resolution of seismic。the author used the generalized S transform to suppress the surface wave, apply the S transform to extract attributes Instantaneous parameters of seismic frequency and instantaneous fractional-dimension parameters of seismic amplitude spectrum.In the paper, the author mainly elaborated on the definition, derivation and characteristics of S transform, and compared the relationships, advantages and disadvantages of S transform,Fourier transform,short time Fourier transform and wavelet transform. Then author reached the following conclusions:There have direct link between S transform and Fourier transform,they both have a lossless reversible; S transform, short time Fourier transform and wavelet transform are all linear time-frequency representation, so there is no cross-term interference; S transform has a variety of resolutions, this make up for the flaw that the short time Fourier transform own fixed resolution; S transform has the phase factor,that associated with the frequency,this overcome the lack of wavelet transform. Finally, the author introduced the improved method of generalized S transform. Based on the above basic theory, the author applied the method of time-frequency analysis to processing and interpretation of seismic data in this paper.In processing of seismic data:According to the generalized S transform and lossless reversible regional characteristics, author applied generalized S transform to suppress surface waves, and compared the results with the high-pass filtering. The author reached the conclusion:The generalized S transform can well suppress surface waves, without loss of effective signal.In explanation of seismic data:As the frequency of actual seismic profiles is complex, and the instantaneous parameters own the information of the subsurface structure and lithology. So it is particularly important to correctly extract the instantaneous parameters. In the paper, author applied S transform to extract instantaneous frequency parameters of underground mined-out area and coal-bed, constructed two models of seismic profiles:one has gob, another not. The author extracted the instantaneous properties of the two model profiles, compared the characteristics of new instantaneous attributes profile with the old attributes profile. On the basis of above, the author got the coal and gob information of models. Finally, the theory is applied to real data, and achieved good results.