2.5-D Modeling in Time Spectral Resistivity Method with a Electric Dipole Source

摘要

A 2.5-D forward algorithm is developed to model responses of polarizable geologic bodies in time spectrum. We derive a new couple of equations with an electric dipole source directly from frequency-domain Maxwell equations. Following previous secondary-field algorithms, the problem is solved by finite element method with triangle mesh and the electromagnetic field responses are gained in the frequency-wavenumber domain. Inverse Fourier transform and inverse Laplace transform are performed for the results in the time and spatial domain. The Cole-Cole model is also introduced to consider induced-polarization (IP). A 2.5-D code is performed in MATLAB and verified by 1-D numerical integration. A typical model of a geologic body is built and the results show that the IP effect can be distinguished during middle and later time. This code is a good tool to evaluate IP anomaly and useful for 2.5-D inversion in future.