Numerical Simulation Study on Influencing Factors and Response Patterns of Loop Source Semi-Airborne Transient Electromagnetic

Abstract

Semi-airborne transient electromagnetic method (SATEM), as an efficient geophysical exploration technique, combines the deep detection capability of ground-based transient electromagnetic methods with the high-efficiency data acquisition advantages of airborne electromagnetic methods. It is particularly suitable for areas with complex terrain, such as lakes, swamps, and mountainous regions. This paper focuses on loop-source SATEM as the research subject. Based on a one-dimensional forward modeling approach, we investigate the influence mechanisms of key factors—including transmitter current intensity, loop-source size, formation resistivity, and flight altitude—on transient electromagnetic signals. The study employs the Finite Volume Method for numerical simulation of a homogeneous half-space model. By constructing multiple sets of comparative experiments, we quantitatively analyze the spatiotemporal evolution characteristics of vertical magnetic field response curves under different parameter combinations. The results indicate that optimal signals can be acquired when the aircraft flies at lower altitudes, transmitter current intensity is maximized as much as possible, exploration is conducted in regions of low formation resistivity, and the most reasonable transmitter side length is selected.