Application of the analytic signal amplitude and the Bott-Smith formula as a simple and very fast depth determination method of gravity anomalies: Application on synthetic and field profile data

Abstract

Determining the depth is one of the most important parameters in interpreting gravity data. Using the maximum values of gravity anomaly and the analytical signal along the profile, the depth of buried anomalies can be calculated. This method is able to determine the depth of gravity anomalies, without considering the initial assumption and the shape of the anomaly. In this method, which is based on the Bott-Smith (BS), instead of using the horizontal gradient (dg/dx) maximum value of gravity, analytic signal (AS) maximum value, has been used to determine the depth of anomaly. In this paper, the top and bottom depth values of gravity anomalies have been determined using residual gravity anomalies along the profile, analytic signal, and synthetic data with and without random errors. In order to confirm the method, Source Parameter Imaging (SPI) and Improved Source Parameter Imaging (ISPI) methods have been used to determine the depth of synthetic and field anomalies. The actual model chosen is considered to be close to the cylinder or sphere. The Tilt-Depth (TD) and modified Hilbert transform methods, have also been used to determine the depth. Finally, after theoretical verification, the methods of Bott-Smith (BS), Improved Bott-Smith (IBS), SPI, ISPI,TD, and Modified Hilbert Transform, are examined on the gravity data collected from the Ajichai area (salt dome) of East Azerbaijan (northwestern Iran). The obtained results complied with the drilling information and Euler Deconvolution method. The most significant advantage of IBS method is the high speed of calculating the depth values, compared to other depth determination methods.