Attenuation Of Near Surface Scattering Waves Research

Scattering waves are formed when seismic wave encounter mutation in the complex near-surface media. Mutations distribute widely in complex area. Ground rolls,direct wave,refraction and reflection wave provide source for scattering waves.Those near-surface scattering waves with high amplitude and wide spectrum strongly contaminate the land seismic data.So it is necessary to carry out research on scattering wave field mechanism and attenuation methods.To study the formation mechanism and characteristics of near-surface wave field scattering wave, elastic wave equation is used to simulate background wave field and strike perturbation field is worked out by perturbation theory.Then scattering wave equation is established based on those two theories.Taking the elastic assumption in account, the frequency spectrum band width is same as the source seismic waves. Its energy is positively correlated with the strength of field background and negative correlated with the distance between source and scattering point. Based on the near-surface scattering wave shape,speed, frequency, distribution and other characteristics of the study,four kinds of de-noising methods are chose of in this study,which are named as frequency-wavenumber domain filtering,wavelet transform,singular value decomposition, LIFT time-distance domain filtering method. The traditional cross-spread cone filter method is ineffective for irregular observation system and insufficient coverage at boundaries of work area.Bigshots cone filter has lower transform distortion, so this method can solve this problem; wavelet transform method needs large amount of computing and requires high computational layers level; singular value decomposition method by linear phase axis correction, using the first a characteristic feature of the image and its corresponding value can be effectively de-noise linear noise,but inevitably mixed with useful information; LIFT time distance domain forward prediction filtering has a simple algorithm, less calculation,and a good de-noising effect.but it requires interference wave has good linear law. When it comes to non-linear interference,linearization correction method is used to ensure the method’s effectiveness.Model data test verify the validity and limitations of the method. The actual data test the feasibility and effectiveness of the LIFT prediction method in time distance domain.