The Study Of Geologic Structure Constrained Tomographic Inversion Based On Gaussian Packet

The aim of seismic exploration is to recognize,locate and describe the underground structure using the seismic wave imaging technology.The inversion and migration is the most important imaging methods,and the accurate velocity model is the guarantee of the accurate locating at the underground structure.Because,in the migration process,we need to make the observed seismic records back propagation in the velocity model to get the seismic profiles,and the more accurate the velocity model is,the more accurate the information of underground structure is;in the inversion process,the accurate initial velocity model can reduce the sparseness of the inversion and improve the efficiency of the inversion.Therefore,the high quality background velocity model plays an important role in the seismic exploration technology.However,the current velocity estimation techniques mainly include the ray tomographic method and the wave equation tomographic method.The ray tomographic inversion still retains the inherent problems of the ray theory,such as caustics,shadows,multi path and cannot traverse the entire model;the wave equation tomography method requires the particularly high initial data and the computational efficiency is very low.In order to solve the above problems,this paper studies a kind of compromise inversion method between ray type and wave equation tomography,which is the tomographic inversion based on Gaussian packet method.This method retains the advantage that the ray tomography has high calculation efficiency,also has the advantage of Gaussian packet's locallization,using Gaussian packets obtain the travel time difference between the observed data and the simulated data,and improve the accuracy and efficiency of inversion.In this paper,based on the theory of Gaussian packet operator,the forward and migration method based on the theory of the Gaussian packet is deduced with the reference of the theory of Gaussian beams.Combined with the principle of ray tomography method and wave equation tomography method,established the objective function on two norm of the travel time difference,calculating the gradient of the objective function of the background model,using optimization method to realize tomographic inversion,realize updating velocity model.In order to further explore the potential of the method in the inversion accuracy,this paper presents a new method which is the geologic structure constrained tomographic inversion based on Gaussian packet.The geological structure constraint method is based on conventional regularization,using geological tectonic attributes(position information of the reflection point and dip information of the stratum corresponding to the position)as a priori information,constructing Gauss smooth matrix up to completion of inversion results constraint.This paper also introduces the method of extracting geological structure information,which is based on the combination of detecting fault method and structural tensor algorithm.Finally,the inversion results of the Gaussian packet tomography inversion method with or without geological structure constraint are compared.It can be seen that the method uses the position information of the reflection point and dip information of the stratum corresponding to the position and reduces the nonlinearity of tomographic inversion.So the geological structure constrained can guarantee the accuracy and stability of the tomographic inversion based on Gaussian packet and makes the inversion result included more geological significance.