A single set of vertically aligned cracks embedded in a purely isotropic background may be con- sidered as a long-wavelength effective transversely iso- tropy （HTI） medium with a horizontal symmetry axis. The crack-...A single set of vertically aligned cracks embedded in a purely isotropic background may be con- sidered as a long-wavelength effective transversely iso- tropy （HTI） medium with a horizontal symmetry axis. The crack-induced HTI anisotropy can be characterized by the weakly anisotropic parameters introduced by Thomsen. The seismic scattering theory can be utilized for the inversion for the anisotropic parameters in weakly aniso- tropic and heterogeneous HTI media. Based on the seismic scattering theory, we first derived the linearized PP- and PS-wave reflection coefficients in terms of P- and S-wave impedances, density as well as three anisotropic parameters in HTI media. Then, we proposed a novel Bayesian Mar- kov chain Monte Carlo inversion method of PP- and PS- wave for six elastic and anisotropic parameters directly. Tests on synthetic azimuthal seismic data contaminated by random errors demonstrated that this method appears more accurate, anti-noise and stable owing to the usage of the constrained PS-wave compared with the standards inver- sion scheme taking only the PP-wave into account.展开更多
为了实现裂隙介质中的地震AVO(amplitude variation with offset)反演,基于Christoffel方程和边界条件,推导了EDA介质中PP波、PS1波、PS2波精确反射系数表达式,并采用扰动法推导了极端弱各向异性介质中PP波的近似反射系数,通过弹性系数...为了实现裂隙介质中的地震AVO(amplitude variation with offset)反演,基于Christoffel方程和边界条件,推导了EDA介质中PP波、PS1波、PS2波精确反射系数表达式,并采用扰动法推导了极端弱各向异性介质中PP波的近似反射系数,通过弹性系数简化得到HTI、裂隙EDA介质中PP波的近似反射系数。模型计算结果表明:在弱各向异性条件下,HTI(horizontal transverse isotropy)介质中地震波的近似反射系数公式计算精度较高,相对误差在4%以内;当裂隙介质在弱各向异性(各向异性系数<0.1)的情况下,当入射角在40°以内时,PP波近似反射系数与精确反射系数的绝对误差在10^(-4)以内,相对误差小于4%,但随着入射角的加大其计算误差有所增加。对各向异性较强烈(各向异性系数达到0.2)的裂隙介质,当入射角相对较小时(小于45°时),裂隙介质中PP波近似反射系数计算式对于强各向异性的介质仍然成立。通过对反射系数的近似研究,可以将裂隙介质中反射系数的非线性问题转为线性问题,进而利用这些特性进行参数反演,有利于提高反演速度。展开更多
The frequency of the Love-type surface waves in a bedded structure con- sisting of a porous piezoelectric (PP) medium and a functionally graded material (FGM) substrate is approximated. The FGM layer is assumed to hav...The frequency of the Love-type surface waves in a bedded structure con- sisting of a porous piezoelectric (PP) medium and a functionally graded material (FGM) substrate is approximated. The FGM layer is assumed to have a constant initial stress. The Wentzel-Kramers-Brillouin (WKB) approximation technique is used for the wave solution in the FGM layer, and the method of separation of variables is applied for the solution in the porous piezoelectric medium. The dependence of the wave frequency on the wave number is obtained for both electrically open and short cases. The effects of the gradient coefficient of the FGM layer, the initial stresses (tensile stress and compressive stress), and the width of the FGM layer are marked distinctly and shown graphically. The findings may contribute towards the design and optimization of acoustic wave devices.展开更多
基金sponsorship of the National Natural Science Foundation of China (No.41674130)the National Basic Research Program of China (973 Program,Nos.2013CB228604,2014CB239201)+1 种基金the National Oil and Gas Major Projects of China (Nos.2016ZX05027004-001,2016ZX05002005-009)the Fundamental Research Funds for the Central Universities (15CX08002A) for their funding in this research
文摘A single set of vertically aligned cracks embedded in a purely isotropic background may be con- sidered as a long-wavelength effective transversely iso- tropy （HTI） medium with a horizontal symmetry axis. The crack-induced HTI anisotropy can be characterized by the weakly anisotropic parameters introduced by Thomsen. The seismic scattering theory can be utilized for the inversion for the anisotropic parameters in weakly aniso- tropic and heterogeneous HTI media. Based on the seismic scattering theory, we first derived the linearized PP- and PS-wave reflection coefficients in terms of P- and S-wave impedances, density as well as three anisotropic parameters in HTI media. Then, we proposed a novel Bayesian Mar- kov chain Monte Carlo inversion method of PP- and PS- wave for six elastic and anisotropic parameters directly. Tests on synthetic azimuthal seismic data contaminated by random errors demonstrated that this method appears more accurate, anti-noise and stable owing to the usage of the constrained PS-wave compared with the standards inver- sion scheme taking only the PP-wave into account.
基金supported by the China Important National Science & Technology Specific Projects (Grant No. 2011ZX05019-008)the National Natural Science Foundation of China (Grant No. 40839901)
文摘The frequency of the Love-type surface waves in a bedded structure con- sisting of a porous piezoelectric (PP) medium and a functionally graded material (FGM) substrate is approximated. The FGM layer is assumed to have a constant initial stress. The Wentzel-Kramers-Brillouin (WKB) approximation technique is used for the wave solution in the FGM layer, and the method of separation of variables is applied for the solution in the porous piezoelectric medium. The dependence of the wave frequency on the wave number is obtained for both electrically open and short cases. The effects of the gradient coefficient of the FGM layer, the initial stresses (tensile stress and compressive stress), and the width of the FGM layer are marked distinctly and shown graphically. The findings may contribute towards the design and optimization of acoustic wave devices.
