A Land-Based Controlled-Source Single-Component Electromagnetic Exploration Method With Finite Scalar Reference Stations

Traditional scalar controlled-source audio-frequency magnetotellurics (CSAMTs) typically calculate Cagniard apparent resistivity based on the amplitude ratio of the horizontal electric field component parallel to the source ( E_{x} ) to the horizontal magnetic field component perpendicular to the source ( H_{y} ). However, when conducting surveys in areas with magnetic metal installations and dense electromagnetic noise, the H_{y} component is more prone to severe data distortion compared to the E_{x} component. In the far-field of a horizontal electric dipole in a uniform medium model, E_{x} is also more sensitive to underground medium resistivity than H_{y} . Recording only E_{x} can enhance the interference resistance and exploration efficiency of the observation system. However, despite the more concise definition of E_{x} apparent resistivity compared to Cagniard apparent resistivity, its susceptibility to source effects is pronounced. Therefore, we have developed a land-based single-component electromagnetic exploration method with finite scalar reference stations. We simulated source effects using several 2-D models and analyzed their impact on E_{x} and Cagniard apparent resistivity. To mitigate source effects associated with using only the Ex component for exploration, we strategically placed a finite number of discrete scalar reference stations to simultaneously measure E_{x} and H_{y} . An improved far-field formula for E_{x} apparent resistivity was derived based on reference observations. Scalar reference stations were positioned in interference-weak areas to ensure data reliability, especi