3D density structure of Sichuan basin, Southwest China based on the inversion of gravity data

Abstract

Sichuan basin is a superimposed basin of marine sediment and continental sediment in Southwest China. The great potential of the deep reservoir in Sichuan basin motivated geophysical studies on the deep structure in this area. Limited by the penetration depth of seismic exploration, the gravity inversion is widely applied to study the deep structure and the density properties. This paper inverted the 3D density distribution of Sichuan basin based on gravity inversion with reweighted regularized conjugate gradient algorithm. The proposed algorithm was tested and verified with two synthetic models. For the application in Sichuan basin, an initial model based on former studies was built to reach a reasonable model in the shallow part structure. The inversion result gave the 3D density structure of Sichuan basin with 60 km in depth. It illustrated the basic layered structure and the horizontal inhomogeneous features from the sedimentary layer to the deep crust. The density features of 7–12 km in depth revealed the basement structure with three parts, which was consistent with the velocity structure on the whole. The high density feature of Dazu area might indicate the local mantle uplift.