3D density inversionof gravity based on unstructured grid and model dimension reduction under undulating terrain
Complex undulating topography and mesh generation method have important influence on gravity inversion and interpretation.At present,the density inversion of gravity is mainly based on vertical cuboid model,which significantly reduces the degree of fitting for undulating terrain and complex geological bodies,and is easy to have a great impact on the gravity inversion and interpretation.The tetrahedral unstructured grid can more accurately simulate the undulating terrain and complex geological bodies.Therefore,this paper studies the 3D density inversion of gravity based on tetrahedral unstructured grid under the undulating terrain.Firstly,the underground area is divided into tetrahedral unstructured grids based on Delaunay's method,and two methods of vertical derivative and correlation coefficient are introduced to model dimension reduction so as to reduce the space of the solution.The objective function is constructed using the minimum length constraint,the depth weighted constraint and the physical range constraint,and solved by the preconditioned conjugate gradient method.In order to improve the inversion efficiency,OpenMP parallel algorithm is introduced.The effects of various constraints and two model dimension reduction methods on the regularized inversion of tetrahedral unstructured meshes are studied.The density inversion of gravity based on tetrahedral unstructured grid can clearly reflect the position of the geological bodies through the experiments of vertical cuboid models at different depths and combined models under undulating terrain.The method proposed in this paper is applied to the iron oxide deposit in Southeast Missouri,USA.The inversion results are in great agreement with the known rock masses,which further proves the correctness and effectiveness of the method.
NETL
NSTL
万方数据
维普
