TTI介质矢量波成像及波型分解

Vector wave imaging and wave separation in the TI media

矢量波成像能够充分利用弹性波场信息,可获得更可靠、更准确的成像结果.本文对TTI介质多分量资料进行矢量波逆时偏移成像处理,从各向异性介质弹性波动理论出发,通过高阶交错网格差分对弹性波方程离散化处理,并将震源波场和检波点波场沿时间方向延拓,再基于局部介质性质求解Christoffel方程,然后将延拓波场沿极化矢量方向投影,得到TI介质中分离的纵横波场,以上述结果作为逆时偏移互相关成像条件中的分量,实现二维多分量地震资料的矢量波叠前逆时偏移,最终得到物理意义明确的P-P和P-SV成像结果.模型试算表明在TTI介质中采用极化投影法分离纵横波场,比基于散度和旋度的分离方法效果更彻底,此外通过算例验证了基于纵横波分解的矢量波成像是一种有效的矢量波场处理技术,成像结果显示该方法获得的信息更丰富,成像更准确.

Vector-wave imaging takes full advantage of information in elastic wavefield,acquiring more reliable and realistic migration results.In this paper multicomponent data in TTI media are processed by the reverse time migration（RTM）.We start from the elastic wave equation theory in anisotropic media,then discrete the elastic wave equation with finite difference of 2-th order in time and 8-th order in space.Continuation of source/receive wavefields along time direction are obtained,then they were projected to the polarization vector through solving Christoffel equation based on local material properties.Finally we realize prestack elastic RTM for2 Dmulticomponent data,by separating P and S wave in TI media,computing imaging condition based on pure P and S wave type,and getting P-P and P-SV imaging results with clear physical meaning.Model tests demonstrate that polarization projection method is better than computing divergence and curl in terms of separating P and S wave,and it＇s also verified that vector-wave imaging based separating different wave types is an effective elastic wavefield processing technique.We testify that this method provides more accurate and richer information.