电场扩散深度法估计固定翼航空瞬变电磁的探测深度

Using Electric Diffusion Depth Approach to Estimate the Investigation Depth of Fixed-wing Airborne TEM

在固定翼航空瞬变电磁系统研制中，系统的探测深度是一项关键的技术指标，需要采用可靠的方法计算它，为系统设计与论证服务。提出一种电场扩散深度法，其估算的系统探测深度大小不受目标层厚度及电性的影响，将系统的探测深度定义为观测响应值高于3倍噪声水平的条件下，地下介质中感应电场幅度的最大值对应的深度。模拟了电场在均匀半空间模型和层状模型中的扩散过程，并根据模型响应大小分析了不同噪声水平和发射磁矩下的系统探测深度，绘制了模型的电导率、噪声水平与探测深度之间的关系曲线，给出了提高系统探测深度的建议。研究思路可用于其它估算电磁法的探测深度，研究结论对固定翼瞬变电磁系统设计有理论指导意义。

In the development of fixed-wing airborne transient electromagnetic system, the investigation depth of the system is a key technical indicator, which needs reliable calculation method using to serve for system design and demonstration. The diffusion depth of electric field method is presented in this paper whose estimates are unaffected by the thickness of the target layer and the resistivity2 In the method, the investigation depth of the system is defined as the corresponding depth of the maximum value of induced electric field amplitude in the earth medium on the condition that the depth the observed response value is higher than the three times noise level. Using the definition, the diffusion process of the electric field in a uniform half-space model or a layered model is simulated and the investigation depths, based on the response of the model, are estimated according to different noise levels and emission moments. The relationship curves between the conductivity of the models, noise level and the system investigation depth are plotted, the suggestion about how to improve the investigation depth is given in the paper. The research ideas can also be used to estimate the investigation depth of the other electromagnetic method, and the conclusion in this paper has the theoretical significance for the fixed-wing transient electromagnetic system design.