Three-dimensional inverse modelling of magnetic anomaly sources based on a genetic algorithm

• Published in: Physics of the earth and planetary interiors 2016-04, Vol.253, p.74-87
• Main Authors: Montesinos, Fuensanta G., Blanco-Montenegro, Isabel, Arnoso, José
• Format: Article
• Language: English
• Subjects: Canary Islands; Estimates; Genetic algorithm; Genetic algorithms; Inverse problem; Inversions; Magnetic anomalies; Magnetization; Mathematical analysis; Mathematical models; Modelling; Potential fields; Three dimensional models
• ISSN: 0031-9201; 1872-7395
• DOI: 10.1016/j.pepi.2016.02.004

•A genetic algorithm scheme is applied to the 3-D inversion of magnetic anomalies.•The approach is valid for uniformly-magnetized sources and isolated anomalies.•The efficiency of the methodology is illustrated with two synthetic examples.•Modelling of aeromagnetic data in Gran Canaria reveals an intrusive body to the NW. We present a modelling method to estimate the 3-D geometry and location of homogeneously magnetized sources from magnetic anomaly data. As input information, the procedure needs the parameters defining the magnetization vector (intensity, inclination and declination) and the Earth’s magnetic field direction. When these two vectors are expected to be different in direction, we propose to estimate the magnetization direction from the magnetic map. Then, using this information, we apply an inversion approach based on a genetic algorithm which finds the geometry of the sources by seeking the optimum solution from an initial population of models in successive iterations through an evolutionary process. The evolution consists of three genetic operators (selection, crossover and mutation), which act on each generation, and a smoothing operator, which looks for the best fit to the observed data and a solution consisting of plausible compact sources. The method allows the use of non-gridded, non-planar and inaccurate anomaly data and non-regular subsurface partitions. In addition, neither constraints for the depth to the top of the sources nor an initial model are necessary, although previous models can be incorporated into the process. We show the results of a test using two complex synthetic anomalies to demonstrate the efficiency of our inversion method. The application to real data is illustrated with aeromagnetic data of the volcanic island of Gran Canaria (Canary Islands).