Study On The Technology Of Extracting Reflection Wave From Seismic Ambient Noise Based On Seismic Interference Method

Seismic exploration is the main technical means to obtain high-precision underground structure information.With the development and progress of society,the traditional seismic exploration technology is subject to more and more restrictions in populated areas.In recent years,seismic interference techniques have been developed continuously and surface wave method using passive seismic ambient noise has been widely used in various exploration scenarios.However,the surface wave exploration method has a relatively low exploration accuracy and cannot meet the needs of high precision exploration.In recent years,the direction of reflection wave extraction based on seismic interference technology has become a new hotspot in the field of seismic interference.Based on the theory of seismic interference,this thesis summarizes the research status of seismic interference method in the field of reflection wave extraction,discusses the interference formation mechanism of the seismic ambient noise volume wave,analyzes the premise and basic assumptions for the acquisition of the seismic ambient noise reflection wave,and through numerical simulation and actual data processing experiments,The main influencing factors and key processing techniques of the seismic interference method for the extraction of reflected waves from seismic ambient noise are studied.The main contents include the following parts:(1)The basic formulas based on the cross-correlation method and deconvolution method are deduced.Based on the basic reasoning of seismic interference,the theoretical mechanism of noise source interference forming reflected waves is analyzed.The stable phase region of noise source distribution suitable for the extraction of reflected waves is discussed.(2)Based on the finite difference algorithm,a numerical simulation method for noise excitation of multiple seismic sources is implemented.The effects of transient noise source,persistent noise source,cross-correlation and deconvolution on the extraction and acquisition of reflected waves were studied by numerical simulation,and the applicability of cross-correlation and deconvolution methods for the extraction of reflected waves from the two kinds of noise signals was compared.The influence of the depth distribution of noise source on the reflection wave extraction is studied.The results show that,for shallow near surface noise sources,the incident Angle of seismic wave range is bigger,can be acquired by using interference method from near offset to the far offset of reflection wave,but the overall gain of reflected wave signal,signal noise ratio(SNR)and with the increase of noise source distribution of deep,seismic wave incident Angle range is smaller,the acquisition of reflected wave interference signal to noise ratio is higher,The distal reflex is gradually missing.The deeper and more connected the noise source is,the closer the seismic wave is to the vertical incidence ground,which is suitable for zero offset interference calculation to obtain zero offset response.(3)Based on actual data processing experiments,the processing effects of cross-correlation and deconvolution interference methods are studied,and the applicability of linear superposition technique and time-frequency phase-weighted superposition technique for the two interference methods is compared.The root mean square error of virtual source records is used to evaluate the convergence effect of data with the increase of stacking time.A data screening method based on power spectral density is proposed,and a transient noise source signal is used to extract the reflected signal.The results show that,among the two interference methods,deconvolution method has a better effect in processing noise data,and time-frequency phase-weighted stacking technique has a higher signal-to-noise ratio.The signal-to-noise ratio of the interference calculation results of the filtered noise data is low,but the discriminable reflected wave signal can also be obtained from it.The zero offset cross-correlation and deconvolution calculation are used to obtain the same zero offset profile as the active source reflection stack profile.