## 5 Numerical Examples  
### Buried Thrust Fault Model  
To validate the imaging workflow shown in Figure 7, a buried thrust fault model is employed first. The schematic diagram of the model and the resistivity of the strata are shown in Figure 8. The geological model primarily consists of two main structures: a shallow ductile rock layer fold and a deep blind thrust fault. A grounded wire, 4 km in length, is used as the transmitter. The coordinates of the two endpoints of the transmitter are (\(-\)2 km, 0 m, 0 m) and (2 km, 0 m, 0 m), respectively. The receiver line, parallel to the transmitter, is 3 km long, with endpoints at (\(-\)1.5 km, 100 m, 0 m) and (1.5 km, 100 m, 0 m). The model includes three low-resistivity layers with resistivities of 100 \(\Omega\cdot\)m, 50 \(\Omega\cdot\)m, and 20 \(\Omega\cdot\)m. Based on the qualitative relationship between the differential pulse width and detection depth, and through extensive experiments, differential pulses with pulse widths of 0.4 ms, 2 ms, and 5 ms are selected as the transmitted waveforms. Figure 9 presents the computational results for square waves with pulse widths of 0.4 ms, 2 ms, and 5 ms. Figure 9a,d,g show bz with low-resistivity anomalies, while Figure 9b,e,h show bz without anomalies. Figure 9c,f,i show the corresponding relative anomaly contours. From the relative anomaly contours, it can be observed that the shallow electromagnetic anomalies for square waves with different pulse widths are more pronounced. Although increasing the pulse width enhances the deep subsurface electromagnetic anomalies, they remain relatively weak. Figure 10 presents the computational results for differential pulses with pulse widths of 0.4 ms, 2 ms, and 5 ms. It can be observed that it is also difficult to directly identify electromagnetic anomalies from the diffusion fields (Figure 10a,d,g). Therefore, relative anomalies are used for illustration (Figure 10c,f,i). When the pulse width is 0.4 ms, Figure 10c clearly reveals the shallow anomalous features of the ductile rock layer fold. As the pulse width increases to 2 ms, the shallow anomalous features of the ductile rock layer fold gradually weaken, while the deeper anomalous features become more prominent (Figure 10f). When the pulse width increases to 5 ms, the anomalous features of the buried thrust fault become more distinct, while the anomalies associated with the ductile rock layer fold become weaker (Figure 10i). By exciting the TEM field with differential pulses of varying pulse widths, electromagnetic anomalies from geological bodies at different depths can be obtained. Comparing Figures 9 and 10, it is observed that the early amplitude of the diffusion fields excited by square waves and differential pulses with the same pulse width is nearly identical, while the amplitude of the square wave diffusion field is stronger in the later stage. However, as shown by the relative anomaly contour plots, the relative anomalies  
Figure 8: Buried thrust fault model. induced by the differential pulse are more pronounced, with an improvement of 53.7% over the square wave (Figures 9c and 10c). The following sections will further compare the virtual wavefields and migration imaging results of square waves and differential pulses with different pulse widths. To simulate field data and perform imaging of electrical interfaces, 5% random noise was first added to the diffusion field, followed by the application of wavelet transform methods to remove the noise interference from the diffusion field.