基于walkaway VSP下行P波的TTI各向异性参数反演

本文基于弱各向异性（WA）介质的正反演公式和qP波的坐标变换，推导了利用qP波反演任意倾斜对称轴的横向各向同性（TTI）介质的各向异性参数和对称轴方向的公式.理论和数值实验表明，利用2个相互正交的变井源距垂直地震剖面（walkaway VSP）可以完全确定钻井中TTI介质qP波的3个WA参数和对称轴的2个方向参数.我们完成了几个由不同数量剖面组成的walkaway VSP模拟实验，使用TTI模型和一般各向异性模型对模拟数据进行了反演，证明了反演公式的正确性和可靠性.使用这些公式，对来自Java Sea的由3条剖面组成的walkaway VSP观测数据进行了各向异性反演，获得了钻井中接收点处介质的WA参数.

Inversion of TTI anisotropic parameters based on walkaway VSP downgoing P-waves

Based on the forward and inverse formulae and coordinate transformation of qP waves in a weakly anisotropic (WA) medium, we derived inversion formulae of anisotropic parameters and symmetric axis direction of TTI (transversely isotropic medium with tilted symmetric axis) medium for qP waves. Both the theory and numerical experiment verify that three independent WA parameters and symmetric axis direction of the TTI medium for qP waves can be completely determined by using a walkaway VSP with two perpendicular profiles. We carried out a simulated walkaway VSP experiment with different numbers of profiles. The TTI model and general anisotropic model were used to invert the data in the experiment. The results show that the derived formulae are correct and reliable. Then a real walkaway VSP observation data from the Java Sea region were inverted, and WA parameters and symmetric axis direction of the TTI medium were obtained by using the derived formulae.