A Joint Inversion Algorithm for the Establishment of High-Accuracy 3-D Marine Gravity Field

Abstract

The 3-D marine gravity field plays an important role in many practical applications, such as matching navigation, object monitoring, and resource exploitation. However, the accuracy of the gravity field generated by most existing methods is relatively low. To solve this problem, this study innovatively puts forward a new method for establishing a high-accuracy 3-D marine gravity field by using a joint inversion algorithm. The presented method incorporates gravity fields observed at different altitudes, especially those observed near the seafloor, because they contain more prominent short-wavelength signals of the sources. The final joint inversion formulas are developed from the standard form of independent inversion of single gravity datasets, so it is conducive to include different weighting matrices. To achieve the efficiency of the presented method, the nonlinear objective function is minimized iteratively using a fast randomized singular value decomposition (RSVD) technique. The employing of RSVD also facilitates the determination of an optimal regularization parameter based on the generalized cross-validation criterion. The presented method is tested on both synthetic gravity fields simulated by a theoretical density model and real gravity fields collected in the South China Sea. Numerical results demonstrate that the presented method can provide more accurate 3-D gravity fields than the commonly used iterative downward continuation method in the wavenumber domain (DCW) and the conventional equivalent source (CES) method.