# Influence of Source Shape on Semi-Airborne Transient Electromagnetic Surveys
## 4 Discussion  
We employed synthetic modeling to analyze how the source geometry influences the SATEM response. A typical curved source configuration was designed to calculate the  
Figure 14: Delay time profile of \(B_{2}\) (A/m) at different offsets for 3D model. Panels (**a–c**) represent curved source response, and panels (**d–f**) illustrate linear source response. Figure 15: Delay time profile of \(\mathrm{dB_{z}/dt}\) (V/m\({}^{2}\)) at different offsets for 3D model. Panels (**a–c**) represent curved source response, and panels (**d–f**) are for linear source response. SATEM electric and magnetic field responses, and its influence on SATEM measurements was systematically evaluated through comparison with the theoretical linear source model response. Initially, we calculated the SATEM electric and magnetic field responses for homogeneous half-space models with both linear and curved sources. The electric and magnetic field distributions of the linear source exhibit straightforward patterns, facilitating a clear comparative analysis of the curved source's influence on SATEM's electromagnetic response. The results demonstrate that upon current termination in the transmitter, the induced currents concentrate predominantly near conductive regions, with electric and magnetic fields displaying spatial distributions that reflect the source geometry. As time progresses, the current diffuses downward, and the influence of the source geometry diminishes. Consequently, the source geometry primarily affects early-time electromagnetic responses in proximity to the source while exerting minimal influence on late-time responses at large offsets. Subsequently, we calculated the SATEM electric and magnetic field responses for a 3D model containing a low-resistivity anomaly. Comparative analysis reveals that 3D conductive anomalies at certain burial depths predominantly affect late-time responses. Notably, the influences of the source geometry and 3D conductive structures on electromagnetic field distributions operate independently of each other. Based on fieldwork design, this paper proposes a curved source that bends along the horizontal plane and investigates its impact on SATEM responses. During actual field exploration, the shape of the transmitting source is constrained by terrain and road conditions, resulting in various curved configurations. Different source shapes produce varying effects on SATEM responses. The source may exhibit significant curvature [29], leading to more pronounced impacts on SATEM responses. Furthermore, terrain undulations can cause the transmitting source to bend in 3D space, creating more complex influences on SATEM responses. Future systematic studies on how different types of transmitting sources affect SATEM responses will enhance our understanding of observational data collected under diverse field terrain conditions. Due to instrumentation limitations, this study only addresses the impact of the source geometry on the vertical component of the magnetic field. [PERSON] et al. [15], through an analysis of ground-based three-component magnetic field response characteristics, concluded that horizontal magnetic field components are more advantageous for 3D target localization. [PERSON] et al. [21] also discussed improvements in the inversion results through three-component observations. In the future, as three-component magnetic field observation equipment becomes more widely available, the influence of the source geometry on horizontal magnetic field components warrants further investigation. Geophysical methods require an inversion interpretation of observational data [7; 8; 9; 29; 30; 31; 32]. The shape of the transmitting source significantly impacts observational data, particularly causing severe distortion in early-time data within small offset regions. Since electromagnetic field information attenuates with offset distance and observation time, the data amplitude is larger in early-time small offset regions and smaller in late-time large offset regions.