A Novel Iterative Stable Algorithm for Global Moho Modeling in the Spherical Harmonic Domain

Abstract The Mohorovičić discontinuity (Moho) marks the boundary between Earth's crust and the underlying mantle, serving as a critical interface for understanding Earth's structure, composition, and geodynamic processes. This study introduces a novel iterative and stable algorithm for global Moho depth inversion. We first derive the gravity disturbance of the Moho interface in the spherical harmonic domain, expressed as a series of spherical harmonic coefficients. These forward expressions are then reformulated into an iterative scheme for Moho depth estimation. To ensure convergence, a damping factor is applied to suppress high‐frequency noise, and the process is constrained by observed gravity data to minimize residuals. The algorithm is validated using a synthetic Airy–Heiskanen interface in a closed‐loop test. Results show stable convergence within approximately three iterations, yielding minimal gravity residuals (∼0.05 mGal) and small depth errors (standard deviation: 0.07 km), demonstrating the method's high accuracy. A sensitivity analysis of constant and variable Moho density contrasts further shows that when density varies from 450 to 600, the mean difference is less than 1.0 km and the standard deviation is only 1.1 km, indicating that the solution is largely insensitive to density changes. Importantly, incorporating a variable density contrast significantly improves Moho depth recovery along mid‐ocean ridges. Finally, the method is applied to refined gravity disturbances that are maximally correlated with Moho depth, successfully recovering global Moho topography. Comparison with the CRUST1.0 seismic Moho model shows strong consistency in both spatial distribution and statistical measures, with depth residuals (standard deviation: 4.23 km) and gravity residuals (∼1.89 mGal), further confirming the robustness of the method. Notably, the use of variable Moho density contrast again provides substantial improvements along mid‐ocean ridges.