Application of gravity interface inversion based on improved 3D varying density model in South China Sea

The gravity data are among the most important data sets for studying deep crustal structures and the tectonic evolution in South China Sea (SCS). The interface inversion by gravity anomalies can effectively estimate the depth of Moho interface and crustal thickness. However, the Moho interface inversion in SCS is facing challenges due to the density contract of crust-mantle drastic vary in three dimensions, which are associated with the complicated crustal styles. To meet the challenges of 3D variation of density in SCS, we present a strategy by joint use an improved variable density model which is composed of multiple polynomials to describe the differences of different crusts and seismic data to be constraints to estimate the Moho depth. We examine the approach with a synthetic example and then apply this strategy to invert the Moho interface in SCS. The constrained variation-density interface inversion results reveal the depth and fluctuation of Moho interface which infers the regional tectonics in SCS. Moreover, we calculate crustal thickness and stretch factor from inversion results to interpret major tectonics in the SCS.