Automatic gravity modeling of sedimentary basins by means of polygonal source geometry and exponential density contrast variation: Two space domain based algorithms

Abstract

Two algorithms are developed in the space domain, using the principles of automatic modeling and inversion, to analyze the gravity anomalies of a sedimentary basin whose cross-section is approximated by a polygonal source geometry within which the density contrast varies according to a prescribed exponential function. Both algorithms perform forward modeling by a technique that combines both analytical and numerical methods because no closed form anomaly equation could be derivable in the space domain using an exponential density function. The proposed algorithms are automatic in the sense that they initiate the structure of a sedimentary basin from the observed gravity anomalies at plurality of observations on the profile and subsequently improve the structure, iteratively, based on the differences between the observed and modeled gravity anomalies within the specified convergence criteria. The proposed modeling algorithm uses simple forward difference approximation whereas inversion solves a system of normal equations to estimate the improvements in the depth parameters of a sedimentary basin. The applicability of each proposed technique is exemplified with a synthetic and a real world gravity anomaly. The advantage of the proposed algorithms is that the observed gravity anomalies need not be specified at equal station interval, which makes the algorithms more user-friendly.