A new approach automatic separation of the Bouguer gravity anomaly, using a new concept for 2D-semi-inversion of the sphere-shaped model

Abstract

ABSTRACT The present research represents a new, fast and easy-to-apply semi-inversion technique for the direct separation of the Bouguer gravity anomaly to its corresponding depths or thicknesses of the prior known rock formations from a borehole (as a control point). As well as the possibility of tracing these formations on the profile points to the Bouguer gravity map according to their density contrasts with basement rock. The proposed method is based on the fact that the sum of the gravitational effect at a point on the Earth’s surface is equal to the sum of the subsurface gravity effects arising from the points of masses of the causal bodies along the vertical line between the Earth’s surface and the basement rocks. In this method, two sedimentary basin models were built based on the distribution of densities from a prior known borehole. Assuming that the depths of the pointed tops of these rock formations can be replaced by the centres of sphere bodies (or point masses) as causative sources of gravitational effect and by the use of a simple algorithm, it was possible to calculate the depths of the rock formations and trace them on the profile, using a new concept called the zero-offset gravity measurement. In this concept, the measuring gravity is vertically above the centre of the sphere-shaped body as it represents the causative source, and its depths are equal to the radius of the sphere body. The present method was assessed on hypothetical models and synthetic data and applied to two real data in field cases which vary in geological and lithological aspects. The first assessed location is Abu Roash Dome Area, southwest Cairo, Egypt, and the second location is the Mors Salt Dome, North Jutland, Denmark.