Improved normalized full-gradient method and its application to the location of source body

• Introduces a new method of selecting the optimal number of harmonics for NFG
• The new method is compared with conventional methods using synthetic models.
• Method applied to the interpretation of gravity anomalies in the Mississippi Salt Basin
• The estimated depth using new method is consistent with previous studies.

The normalized full-gradient (NFG) method is useful for estimating the source position in semi-quantitative gravity interpretations. Several studies using the NFG method to recover source parameters have shown that this method can reliably locate sources but in practice it is difficult to choose the optimal number of harmonics to act as a smooth filter. In this study, a versatile method was developed for determining the optimal number of harmonics for the NFG method. The optimum harmonic number is determined by analyzing two combined curves: the energy ratio curve of the reconstructed anomalies and the depth curve, along with the change in the number of harmonics. This method was tested and compared with the conventional method on synthetic models, with satisfactory results. When applied to real data from a gravity profile normal to the mid-point of an elongated salt wall in the Mississippi Salt Basin, the estimated source position was consistent with seismic information and previous studies.