QS-FDTD Modeling of Dispersive Superparamagnetic Soils for Time-Domain Electromagnetic Method

Abstract

Time-domain electromagnetic (TDEM) method is extensively utilized in geophysical surveys for detection of groundwater and mineral deposits. However, the dispersive effect of superparamagnetic (SPM) soils significantly impacts performance of these systems. In modeling of the SPM soils, the distribution of magnetic particles in the soil is generally accounted with a log-uniform model in which time-relaxation constants are distributed uniformly in a finite time range. In this study, the effect of the SPM soils on the TDEM system performance is analyzed by a quasi-static finite-difference time-domain (QS-FDTD) method. The treatment of the magnetic dispersive SPM soil of the log-uniform model is performed by an auxiliary differential equation (ADE) technique (without any convolution) in the QS-FDTD method. The numerical results are validated for a homogeneous SPM half-space problem and a problem of a thin SPM upper layer with a buried conductive body. Afterward, a dispersive complex problem is also solved. The obtained results can be used to evaluate the TDEM performance for the complex magnetic dispersive problems.