The Study Of Seismic Wave Propagation In EDA Medium And Parameters Inversion

Fractured media is the most common media in engineering. The density,characteristics and distribution of fracture have important effects on stability of rocks and safety of engineering. Fractured rocks is often abundant with groundwater and it's stability is poor and often cause water gushing or collapse. Seismic exploration is the one of most effective method in fracture detection and rock quality assessment.Traditionally,the media is assumed to be totally isotropic, but in fact they are essentially anisotropic.This assumption may lead to erroneous imaging, thus affecting the accuracy of exploration results. In order to improve the inversion accuracy and satisfy the trend of fine exploration, the research of the seismic anisotropy and the characteristics of seismic wave propagation is becoming more and more urgent and has becoming one of the hot and challenge topics of seismology.Firstly, the exact formula of phase velocity and group velocity for the HTI media are derived from VTI media, then the similarities between HTI and VTI are discussed. This similarities are used to derive the calculation formulas of EDA media. Starting from HTI media,the exact formula for phase and group velocity are derived using Bond transfer. Based on perturbation theory, the weak anisotropy approximate formula for phase velocity, group velocity of HTI, EDA media are derived with isotropic media as the background media.Starting from christoffel equation, the exact formula for reflection coefficients of P, SV, SH waves in EDA medium are derived considering the Boundary conditions, stress-strain relationship. The approximation formula for the reflection coefficient of P wave in EDA media are derived using perturbation method with isotropic media as the background media.Based on the study of casion and Du qizheng the derive of the wave equation for viscoelastic EDA media is described.With the real ray tracing method proposed by Vavrycuk,the wavefield in EDA media was simulated successfully.Using the mixed specification,the exact formula for phase velocity slowness and polarization of P,SV,SH-wave both in HTI and EDA media are derived from Christoffel equation and the characteristics of SH-wave phase velocity varying with the changing of inhomogeneity angle are studied.The approximation formula for phase velocity, group velocity and polarization vector are derived by Perturbation method with elastic anisotropic media as the background media. The exact formula for phase and group attenuation coefficients of homogeneous and inhomogeneous seismic wave are derived from christoffel equation.Starting from the formulas of VTI, the nonhyperbolic quation and the formula for DMO velocity in HTI,EDA media are derived and with this formula the relation between NMO velocity and azimuth,anisotropy parameters,dip angle become clear.Multi-layer diping EDA model is used as an example for elastic parameters estimation and the geometric parameters of the interface are decided by traveltime and raytracing,the error of the inversion result are analysised, then the anisotropic parameter is used to calculate the fracture density and forecast water content.Finally,the geology exploration for yunyan shan tunnel verified that the inversion algorihm is feasible,the inversion result are reliable and accuracy.