Rectangular harmonic analysis for gravity field representation by fusing ground gravity and airborne gravity gradient tensor data: A case study in Vinton salt dome, USA

Abstract

Gravity and Gravity Gradient Tensor (GGT) surveys are commonly used to investigate mineral deposits, oil and gas reservoirs, etc. However, the different kinds of discrete observations with unknown noises are usually irregularly and unevenly spaced. Therefore, the practical observations need to be self-consistently and reliably fused and then the regularly distributed grid data of desired physical quantity can be predicted by the data fusion method. Rectangular Harmonic Analysis (RHA) is one of efficient and easy-to-implement methods for data processing, gravity field representation and so on. Combining ground gravity and airborne GGT data to determine RHA coefficients is beneficial for improving the reliability of complete wavelength components of the gravity field. In this study, we employ the modified RHA method to recover the gravity field by fusing ground gravity and airborne GGT data sets. Through a series of tests with synthetic data, we discuss the option of maximum RHA order, data sampling spaces and performances by using different simulated data sets assemble to represent the gravity field under different practical conditions. The synthetic tests show that the RHA can effectively extract the coherent signals as far as possible from the different data sets and guarantees better fitness between the predicted gravity and GGT data to observed data. Finally, we apply the RHA method to practical ground gravity and airborne GGT data sets over the Vinton salt dome, Louisiana, USA, to represent and predict the gravity and GGT data sets at different altitudes over the study region. As an example of geological application, the predicted GGT data sets are employed to interpret the lithological boundaries with density contrasts beneath the study area.