# Influence of Source Shape on Semi-Airborne Transient Electromagnetic Surveys
## 3 Results
### 3D Model
#### 3.2.2 Magnetic Fields in the Air  
Figure 12 illustrates the \(B_{z}\) distribution in the plane within the airborne receiving area at various time instants, where Figure 12a-c represent the curved source responses, and Figure 12d-f depict the linear source responses. A comparative analysis of Figures 5 and 12 reveals that the 3D conductive body predominantly influences the \(B_{z}\) response at 0.01 s. The distributions shown in Figure 12c,f exhibit remarkable similarity, both clearly displaying anomalies attributable to the 3D conductive structure, while a subtle oblique distribution of the magnetic field is observed in the proximal region. The magnetic field distributions at \(10^{-5}\) s and \(2.5\times 10^{-4}\) s closely resemble those of the homogeneous half-space model, with the influence of the source geometry being distinctly visible in regions of small offset,  
Figure 11: Electric field (V/m) in oyz plane for the 3D model at different time instants. Panels (**a–c**) represent the curved source response, while panels (**d–f**) illustrate the linear source response.  
whereas the impact of the 3D conductive structure on the magnetic field remains negligible at these earlier times.  
Figure 13 presents the \(dB_{z}/dt\) distribution in the plane within the airborne receiving area at various time instants, where Figure 13a-c represent the curved source responses, and Figure 13d-f depict the linear source responses. In comparison with \(B_{z}\), the \(dB_{z}/dt\) component exhibits analogous characteristics: the source geometry predominantly affects \(dB_{z}/dt\) at small offsets, while the 3D conductive structure influences \(dB_{z}/dt\) at large offsets at the later time of 0.01 s.  
To further elucidate these relationships, we present the delay time profiles of the magnetic field responses along different offset lines. Figure 14 displays the delay time profiles of \(B_{z}\) responses at various offsets. Figure 14a-c correspond to the curved source responses at 200 m, 500 m, and 800 m, respectively, while Figure 14d-f correspond to the linear source responses at the same respective offsets. Similarly, Figure 15 presents the delay time profiles of \(dB_{z}/dt\) responses at various offsets. Figure 15a-c correspond to curved  
Figure 12: \(B_{z}\) (A/m) in the plane within this airborne receiving area for the 3D model at different time instants. Panels (**a-c**) represent the curved source response, while panels (**d-f**) illustrate the linear source response.  
Figure 13: \(dB_{z}/dt\) (V/m\({}^{2}\)) in the plane within this airborne receiving area for the 3D model at different time instants. Panels (**a-c**) represent the curved source response, while panels (**d–f**) illustrate the linear source response.  
source responses at 200 m, 500 m, and 800 m, respectively, while Figure 15d-f correspond to linear source responses at the same respective offsets. These multichannel profiles illustrate the temporal evolution of the magnetic field from early times (10\({}^{-5}\) s) to late times (0.01 s). A comparative analysis of Figures 14 and 15 with Figures 9 and 10 clearly demonstrates that the source geometry primarily induces distortion in the early-time magnetic field responses along the measurement profile, whereas the 3D conductive structure predominantly causes an enhancement of the late-time magnetic field responses along the same profile.