Inversion of the lateral density variations of the lithosphere using the full gravity gradient tensor

Abstract

Flexural isostasy is commonly used to understand the relationship between the observed topography, the crustal structure, and the gravity. Compared to local isostasy, flexural models behave like low-pass filters on the crust-mantle interface. Using this methodology different internal structures are revealed showing the geometry of crustal and lithospheric structures. In the current flexure studies it is assumed that the lithosphere has uniform densities. The misfit between this method and the observed gravity data could be used to invert for lateral densities in the lithosphere.  In this study spectral analysis on the topographic and gravity results from the flexural models is performed to study the effect of lateral variations. For the inversion we use the full tensor of the gravity gradient as they show more sensitivity to the lithosphere structures. The inversion technique is based on spectral kernel models that are able to depict the sensitivity of satellite gravity data. Extensive synthetic analysis is been performed to acquire the best inversion settings and to study the uncertainty of the inversion results with respect to the chosen flexural model. A two-layer lateral density model (crust – upper mantle) is applied to the Sunda Subduction zone to yield more insights into the density structure of the subducting plate.