Abstract：Vertical seismic profile (VSP) data boast a high signal-to-noise ratio and accurate depth information. Information such as traveltime in VSP data can be used to obtain vertical transversely isotropic (VTI) and tilted transversely isotropic (TTI) anisotropy parameters of the formation through inversion. However, it is difficult to determine arbitrary anisotropy parameters in this way. Polarization and slowness vectors are direct parameters that characterize the elastic matrix in the Christoffel equation and can be measured by VSP without being influenced by overlying strata. VSP also enjoys an advantage in accurate depth information. Therefore, it is available for obtaining arbitrary weak anisotropy parameters of a medium through inversion. To start with, we present a solution method for the Christoffel equation based on the perturbation theory and introduce forward and inversion formulas for slowness and polarization vectors of the qP wave. Then, we provide a high-precision acquisition method for slowness and polarization vectors based on Walkaway VSP mea-surement. Finally, a weighted iterative inversion algorithm for arbitrary weak anisotropy parameters is proposed. A maximum of 15 weak anisotropy parameters are worked out with model data, and the results are highly consistent with the theoretical values. Application on field data further shows that the proposed method, with high precision, applies to extraction of seismic anisotropy parameters.
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