Three-dimensional density structure of North China's craton crust and its geological implications

One of the goals of geological interpretation on gravity anomalies is to reveal three-dimensional density structure of the earth's crust, for which density inversion is crucial. This paper presents multiple-scale density inversion of gravity anomalies. Firstly wavelet transform is employed to decompose gravity anomalies. Secondly, power spectrum analysis is performed to estimate the average depth of the field source for each layer, and then the generalized density inversion method is used to calculate the depth of each layer. Finally, such multi-scale density inversion is conducted for the North China region, resulting in the density structure of its crust. The results demonstrate that this approach is effective. The followed analysis indicates that low density anomalies in orogenic belts mainly reflect the granite bodies distributed there. In comparison with shallow density disturbance in eastern North China, depressions bearing oil and gas seem to have low-density anomalies of small amplitude. It implies that the density information extracted by wavelet multi-scale inversion has some guiding significance for deployment of oil and gas exploration.