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Global and regional surface‐wave inversions: A spherical‐spline parameterization

A surface‐wave phase‐velocity inversion scheme based upon a compactly supported cubic B‐spline basis on a triangular grid of knots with approximately equal inter‐knot spacing is implemented to perform global, regional and variable resolution inversions. Numerical results show that the inverted phase‐velocity maps based upon this method are similar to those obtained using a global spherical‐harmonic representation. Nonlinear inversions incorporating ray refraction are feasible based upon the spherical‐spline model parameterization and the resulting maps are only slightly different from those based upon the great‐circle approximation. A multiresolution analysis is introduced to obtain finer resolution in regions with good ray coverage and lower resolution in regions with poor coverage.