Amplitude inversion of the 2D analytic signal of magnetic anomalies through the differential evolution algorithm

Abstract

In this work, analytic signal amplitude (ASA) inversion of total field magnetic anomalies (TMA) has been achieved by differential evolution (DE) which is a population-based evolutionary metaheuristic algorithm. Using an elitist strategy, applicability and effectiveness of the proposed inversion algorithm have been evaluated through the anomalies due to both hypothetical model bodies and real isolated geological structures. Some parameter tuning studies relying mainly on choosing the optimum control parameters of the algorithm have also been performed to enhance the performance of the proposed metaheuristic. Since ASAs of magnetic anomalies are independent of both ambient field direction and the direction of magnetization of the causative sources in two-dimensional (2D) case, inversions of synthetic noise-free and noisy single model anomalies have produced satisfactory solutions showing the practical applicability of the algorithm. Moreover, hypothetical studies using multiple model bodies have clearly showed that DE algorithm is able to cope with complicated anomalies and some interferences from neighbouring sources. The proposed algorithm has been then used to invert a small- (120 m) and a large-scale (40 km) magnetic profile anomalies of an iron deposit (Kesikkopru-Bala, Turkey) and a deep-seated magnetized structure (Sea of Marmara, Turkey), respectively to determine depths, geometries and exact origins of the source bodies. Inversion studies have yielded geologically reasonable solutions which are also in good accordance with the results of normalized full gradient (NFG) and Euler deconvolution (EUD) techniques. Thus, we propose the use of DE for not only the amplitude inversion of 2D analytical signal of magnetic profile anomalies having induced or remanent magnetization effects but also the low-dimensional data inversions in geophysics.