地空频率倾子测深法及一维正演特征分析

为了充分利用地空频率域电磁法的三分量磁场信息，参照大地电磁法倾子测量技术，提出了一种地空频率倾子测深方法。首先，从水平电偶极子在一维层状介质中的全空间磁场公式出发，推导了地空频率倾子两个分量T_x、T_y的表达式，并通过快速汉克尔变换实现地空频率域倾子响应的一维正演；然后，对典型层状模型进行一维正演模拟，分析地空频率域倾子响应特征。通过分析均匀半空间模型和一维层状模型的正演结果，得到如下结论：①倾子响应整体沿场源方向及其垂直方向对称，同时存在场源畸变和过渡带畸变效应；②随收发距增大，倾子响应形态基本保持不变，幅值快速减小；③飞行高度变化时，倾子虚部幅值保持不变，实部幅值快速减小；④通过测量不同频率的倾子响应能够有效研究地下介质电阻率的垂向变化；⑤地空频率倾子测深法应在远区观测，可尽量避开畸变效应区，并合理选择T_x和T_y分量进行解释。文中模拟分析证明了该方法的理论可行性和有效性，为地空电磁法提出一种可能的发展方向。

Ground-airborne frequency tipper sounding method and charactersitics analysis of its one-dimensional forward modeling

To fully utilize the three-component magnetic field information of the ground-airborne frequency-domain electromagnetic method, this paper proposes a ground-airborne frequency tipper sounding method by referring to the magnetotelluric tipper measurement technology. Starting from the full-space magnetic field formula of the horizontal electric dipole in the one-dimensional (1D) layered medium, we derive the expressions of the two components T_x and T_y of the ground-airborne frequency-domain tipper, and the 1D forward modeling of a typical layered model is conducted to analyze the response characteristics of the ground-airborne frequency tipper. Through the analysis on the forward modeling results of the uniform half-space model and 1D layered model, the following conclusions are drawn:① The tipper response is symmetric along the field source direction and vertical direction as a whole, and the distortion effect of the field source and the transition zone exists si-multaneously; ② With the increase in transmitter-receiver distance, the tipper response form basically remains unchanged, and the amplitude decreases rapidly; ③ The amplitude of the imaginary part of the tipper remains unchanged while the amplitude of the real part drops rapidly as the flight height changes; ④ The vertical variation of the resistivity of underground media can be effectively studied by measuring the tipper response of different frequencies; ⑤ The ground-airborne frequency tipper sounding method should be applied at a long distance to avoid the distortion effect area as far as possible, and components T_x and T_y should be rationally selected for interpretation. The theoretical feasibility and effectiveness of this method are proved by simulation analysis, and this method could be a possible development way for the ground-airborne electromagnetic method.