A Parallel Goal-oriented Adaptive Finite Element Method For 2D Marine EM

We present a parallel goal-oriented adaptive finite element algorithm that can be used to rapidly compute highly accurate solutions for 2.5D controlled-source electromagnetic (CSEM) and 2D magnetotelluric (MT) modeling problems. The use of an unstructured triangular modeling grid allows for efficient use of mesh nodes for discretizing arbitrarily complex domains. A goal-oriented error estimator based on the dual residual weighting method computed through hierarchical bases provides robust error estimation that is used to guide an iterative adaptive mesh refinement process. Our formulation of the error estimator considers the relative error in the strike aligned fields and their spatial gradients, and therefore results in a more efficient use of mesh nodes than previous error estimators based on absolute field errors. This algorithm has been parallelized over frequencies, transmitters, receivers and wavenumbers, enabling it to achieve accurate solutions in run-times of seconds to tens of seconds for realistic models and data parameters when run on cluster computers of up to a thousand processors. Application of this new algorithm to a complex model that includes strong seafloor topography variations and multiple thin stacked reservoirs demonstrates the performance and scalability on a large cluster computer.