Magnetic anomalies are interpreted for subsurface geological information. Three-dimensional inversion of magnetic data is a challenging quantitative approach for interpreting the data. The rapid iterative migration technique could be a good and fast alternative for the inversion method. The focusing iterative migration that employs a focusing stabilizer can generate focused migration models which justify geological interfaces, adequately. This paper introduces a new algorithm using a relaxed steepest descent method and a sigmoid stabilizer for fast focusing migration of magnetic fields. The developed method can improve the computational efficiency of focusing iterative migration by reducing the required iterations. The better performance of the new method is demonstrated by two numerical models and a real case study. The magnetic anomaly over San Nicolas massive sulfide deposit in Mexico is used for the case study. Compared with the drilling information, the iterative migration methods produce robust migration models for the San Nicolas deposit.
