First-order perturbation approximation of azimuth converted wave reflection coefficient of HTI media
LIU Hongying1, WU Guochen1,2, SHAN Junzhen1, YANG Sen1
1. School of Geoscience, China University of Petroleum(East China), Qingdao, Shandong 266580, China; 2. Evaluation and Detection Technology Laboratory for Marine Mineral Resources, Qingdao, Shandong 266071, China
Abstract：Depending on separate research purpose,scholars simplified and approximated the Zoeppritz equation.However,most of the approximate equations cannot accurately describe the changing laws of the amplitude of PSV wave at a large incident angle.And due to seismic data changing with azimuth,research on the azimuth reflection coefficient of PSV wave is relatively weak.Based on the precise expression of the reflection / transmission coefficient of HTI media,according to the theory of medium decomposition and perturbation,and assuming weak anisotropy,we derived an approximate expression of the reflection coefficient of PSV wave,analyzed the amplitude azimuth through forward modeling,and discussed the sensitivity of azimuthal PSV reflection coefficient to anisotropic parameters.Forward modeling shows that: ①At a small incident angle,the azimuth of the reflection coefficient is not obvious,and changes in anisotropic parameters have little effect on the reflection coefficient; however,as the increase of the incident angle,the characteristics of the reflection coefficient changing with the azimuth become more obvious,and the reflection coefficient is affected by the change of anisotropic parameters; ②The greater the contrast between the anisotropic parameters of the media above and below an interface,the more obvious the reflection coefficient changes with azimuth; ③γ(V) (related to the velocity difference in vertical and horizontal propagation of S-wave) has the greatest effect on the reflection coefficients,and ε(V) (related to the velocity difference invertical and horizontal propagation of qP-wave) has the least effect on the reflection coefficient,and the effect of anisotropic parameters on the reflection coefficient is related to azimuth.
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