A Study on Three-Dimensional Resistivity Model Construction Based on Spherical Radial Basis Function Interpolation

The spatial distribution of strata under nappe tectonic conditions is highly complex. Conventional approaches, such as dense borehole exploration or intensive in situ investigation, are often costly and difficult to implement for revealing detailed stratigraphic structures. To address this issue, this study focuses on the nappe tectonic setting of the main orebody in the Kambove mining area and proposes a spherical radial basis function interpolation method incorporating spatial anisotropy to construct a three-dimensional resistivity model, thereby providing a data foundation for subsequent intelligent stratigraphic identification. First, the discrete resistivity measurement points were processed through coordinate unification, elevation correction, and data quality inspection. Then, based on radial basis function interpolation theory, a spherical kernel function and anisotropic ellipsoidal constraints were introduced to achieve the three-dimensional continuous representation of discrete resistivity data. Finally, the interpolation performance of the proposed method was compared with that of linear RBF interpolation and inverse distance weighting with P=2 and P=3 using random holdout validation. The spherical RBF method yielded an ME of −12.2 Ω·m and the lowest RMSE of 299.0 Ω·m, corresponding to RMSE reductions of 13.6–22.0% relative to the comparison methods. These results indicate that the spherical RBF method provides better local interpolation performance within areas covered by existing measurements. The proposed method preserves the continuity and smoothness of the resistivity field and enhances its representation along the dominant geological structural direction, thereby providing a continuous three-dimensional resistivity basis for subsequent intelligent stratigraphic identification.