In this paper, an independently developed device system called Surface Electromagnetic Prospecting (SEP) system was introduced through a CSAMT test at Dongguashan copper mine, east of Tonglin, Anhui province. In this area exists a strong electromagnetic interference including mineral and other human interferences, so there is a big challenge for electromagnetic exploration field work. In order to test the anti-interference ability of our system and ensure the quality of data, we applied both spectral analysis and temporal filter methods to improve the signal-to-noise ratio. After data processing, we obtained better results in our geophysical models and showed that the SEP system is able to obtain stable and reliable data in a complex and noisy environment. Consequently, the anti-interference capability of the SEP system is capable to undertake complicated exploration tasks.

In underwater electromagnetic communications, geophysical electromagnetic exploration, and other fields, the conduction current in the medium is much larger than the displacement current. In this case, the electromagnetic waves follow the diffusion field equation. For the simulated region truncation of the diffusion field, traditional perfectly matched layers for the wave equation in media that are dominated by displacement currents are not applicable. In this paper, a new perfectly matched layer metric for the diffusion field is proposed, and its parametric form is given, which is completely different from the conventional perfectly matched layer formation. The parametric form is related to the frequency and conductivity of the medium and is suitable for wide frequency band and media with large conductivity ranges. The spatial distribution of characteristic parameters and the method to find the optimal characteristic parameters are introduced. The numerical experiments for one-, two-, and three-dimensional radiation or scattering problems verify the validity and precision of the perfectly matched layer through a comparison with traditional methods or analytic solutions. Through the truncation performance of different models, it is concluded that the proposed perfectly matched layer metric is stable and can provide a good truncation performance for the diffusion field.

Airborne transient electromagnetic (ATEM) technology is a technique often used in mineral exploration and geological mapping. Due to inductive polarization (IP) phenomena, the ATEM response curve often shows a negative response or declines rapidly to the attenuation curve. Traditional resistivity inversion techniques do not explain the IP response of a signal well, so the negative response is usually removed during data processing, resulting in a reduced correctness and authenticity of the findings. In this paper, in the parameter inversion based on the Cole–Cole model, the Jacobian matrix chain analysis method is used to calculate, and the current waveform calculation is also considered in the inversion. The results show that compared with the perturbation method, the analysis technique can greatly reduce the calculation time and improve the inversion efficiency. In the single-point one-dimensional inversion and lateral constraint quasi-two-dimensional inversion, the Cole–Cole four-parameter forward response has strong inversion accuracy, which can successfully invert the actual exploration content and the Cole–Cole four-parameter response. Some measured sounding data in the Qingchengzi survey area of Liaoning Province, China have a negative response to IP, and the resistivity scheme cannot be used alone for inversion, but the real underground resistivity structure can be obtained through the method studied in this paper, and good exploration results can be obtained.

In geophysical inversion issues, the Jacobian matrix computation takes the greatest time, and it is the most significant factor limiting the inversion’s calculation speed. We think that the correctness of the inverse problem is determined by the difference between the inversion data and the real data, not the precision of the gradient solution in each iteration. Based on this, we present an approximate computation approach for the Jacobian matrix that may rapidly solve the inverse issue by estimating the gradient information. In this research, the approximate gradient information is solved in each iteration process, and the approximate gradient is utilized for computation; nevertheless, the poor fitting of the evaluation data is correctly evaluated, and the inversion model that fits the criteria is achieved. We employed this approach of estimating the Jacobian matrix to invert the 3D airborne transient electromagnetic method (ATEM) on synthetic data, and it was able to significantly minimize the time necessary for the inversion while maintaining inversion accuracy. When the model mesh is more precise, this technique outperforms the previous way of finding the exact Jacobian matrix in terms of acceleration.