3D Full-wave Forward Modelling for Ground Transient EM Methods

The traditional convolution algorithm has been successfully applied to transient electromagnetic (EM) full-wave forward modeling. However, for calculating the magnetic induction dB/dt responses, we need the second order of derivative of the transmitting current in high-precision. This can be problematic and instable, especially when modeling the practical transmitting waveform. In this paper, we introduce the time-domain 3D unstructured finite-element method to implement the forward modeling for ground transient EM system. We simulate the full-wave responses of arbitrary transmitting waveforms by directly applying the instantaneous current for each time channel to the source term of the diffusion equation of the electrical field. This avoids the second order of derivative of the transmitting current and vastly improves the stability of the simulation. We check the accuracy of our algorithm against a ID semi-analytical solutions for a triangular wave and comparing our results with those from the convolution method for a half-space model with an abnormal body embedded.