3D Joint Inversion Of Gravity Gradiometry And Magnetic Data In Spherical Coordinates

The earth observation satellite is the most favorable tool for the study of large-scale regional earth sciences. The GOCE satellite launched by European Space Agency has been able to obtain the earth gravity gradient tensor data by which is equipped with high precision gravity gradient measurement instrument. Compared with the traditional gravity data, it can reflect more accurate earth interior density distribution. The newly launched SWARM satellite group is able to observe the precise geomagnetic field. The newly and high precision dataset moves the related data processing methods getting developed. The development of three-dimensional inversion theory in the geophysical exploration has been applied to satellite data, and used for the study of large scale geophysical problems. This paper aims to study the joint inversion in the spherical coordinates to recover the large-scale regional or global lithospheric structure through combining these new gravity gradient and geomagnetic observation data.This paper starts with gravity gradient data, on the basis of previous research work, by using the Tikhonov regularization theory, the inversion objective function is established combing with the gravity gradient data misfit function and the spherical coordinate model. And, the inversion density parameter boundary constraint is added in. The logarithmic barrier method is used to solve the constrain optimization problems of the gravity gradient inversion in spherical coordinate systems. Moreover, the validity of the inversion method is verified by a set of simple theoretical model tests. Based on the inversion method of gravity gradient data in the spherical coordinate system, the second part of the paper considers that the density and magnetic properties of the same area correspond to the distribution of the same geological structure, which has similarity on the structure. The cross-gradient joint inversion method of geophysical exploration in the Cartesian coordinate system is induced to the spherical coordinate system. Then I construct the cross-gradient joint inversion of gravity gradiometry and magnetic data corresponding to the Tesseroidal cells in the spherical coordinates. In the following, the third part is mainly for the high remanent magnetism of the ocean regions during the inversion of large scale lithosphere magnetic structure. The magnetic anomaly modulus data with weak dependence on the magnetization direction are used combining with the gravity gradient data to construct the cross-gradient joint inversion problem. Then both the joint inversion density and magnetic structure of mutual constraint can be obtained. The effect of remanence can be suppressed and the density structure can be improved, at the same time. In order to solve the joint inversion problem, this paper induced the new spectral projection gradient method, and the boundary condition is added to solve the problem iteratively.The last part of the paper is the application of real satellite data inversion and interpretation. Firstly, the satellite gravity gradient data is used to inverse the density structure of the whole North America. Then the Tibetan Plateau is chosen to inverse its the lithospheric density and geomagnetic structure using the gravity gradient and magnetic anomaly △T data. Finally, the gravity gradient and magnetic amplitude are used to recover the lithospheric density and magnetic structure of the Philippine Sea plate with strong residual magnetism.