A wavenumber-domain iterative approach for apparent density mapping of an undulant layer and its application in central South China

Abstract

Apparent density mapping is a technique to invert the gravity anomaly for obtaining the density distribution in the subsurface layer. The conventional approach for apparent density mapping usually assumes that the top and bottom interfaces of the layer are flat and horizontal, which is not often the case in the real world. We have developed a wavenumber-domain iterative approach for mapping a density distribution of the undulant layer, whose top and bottom interfaces could be a variable relief. The wavenumber-domain approach requires that the observational surface of the gravity data is flat and horizontal. The wavenumber-domain equations for forward calculation of the gravity anomaly due to the undulant layer and its inversion are presented. A damping factor is adopted in the inversion equation for suppressing high-frequency noise in the data and stabilizing the mapping. We use an iterative algorithm for mapping to minimize the difference between the observed and calculated gravity anomalies and to optimize the density values within the layer. The presented approach is simple, fast, stable, and easy to operate. A test on the synthetic data and the real data from the Xuefengshan tectonic zone in central South China verified the feasibility of our approach with higher accuracy than the conventional wavenumber-domain mapping approaches and higher efficiency than the conventional space-domain mapping approach.