Result of a synthetic recovery test of tomographic inversion with a 1-D heterogeneous and anisotropic model. (a) 1-D distribution of P-wave velocity (V_P(0)) of V_MOD. The velocity–depth function is additionally shown as a black graph between vertical lines (2, 3 and 4 km s⁻¹). (b) Result of velocity inversion using simulated P-wave traveltimes in model V_MOD and using the source–receiver combinations as in the measured tomographic data set. (c) Error of velocity inversion compared to real velocity model. (d) Standard deviation of inverted velocity values for each gridpoint based on statistics of all Voronoi cell models used to compute the final result by averaging. (e) Absolute value of the P-wave velocity gradient. (f) RBP from analysis of all Voronoi cell models used for the result.