3-D electromagnetic modeling and nonlinear inversion

We describe a new algorithm for 3-D electromagnetic inversion that uses global integral and local differential equations for both the forward and inverse problems. The coupled integral and differential equations are discretized by the finite element method and solved on a parallel computer using domain decomposition. The structure of the algorithm allows efficient solution of large 3-D inverse problems. Tests on both synthetic and field data show that the algorithm converges reliably and efficiently and gives high-resolution conductivity images.