The Efficient Hybrid Mixed Spectral Element Method With Surface Current Boundary Condition for Modeling 2.5-D Fractures and Faults

Fast electromagnetic (EM) simulation of thin layers, such as geological fractures and faults, is still a challenge since the local mesh refinement near such structures dramatically increases the number of degrees of freedom (DoFs), thus large computational resources are required for modeling their interactions with electromagnetic fields. Therefore, significant attention has been paid to overcome the problem. In this work, we propose the 2.5 dimensional hybrid mixed spectral element method with a surface current boundary condition (the 2.5-D hybrid MSEM-SCBC) to accelerate the simulation and utilize it for the low-frequency solutions of electromagnetic field in subsurface sensing. By introducing SCBC to model the EM field diffraction, the geological fractures and faults are represented geometrically by zero-thickness sheets instead of finite thickness thin layers to avoid local mesh refinement, and to significantly decrease DoFs and computational costs. Numerical results demonstrate that the proposed method is efficient and accurate in simulation of 2.5-D subsurface sensing problems.