Abstract
Abstract Transient electromagnetic method (TEM) is often used in urban underground space exploration and field geological resource detection. Inversion is the most important step in data interpretation. Because of the volume effect of the TEM, the inversion results are usually multi-solvable. To reduce the multi-solvability of inversion, the constrained inversion of TEM has been studied using the least squares method. The inversion trials were performed using two three-layer theoretical geological models and one four-layer theoretical geological model. The results show that one-dimensional least squares constrained inversion is faster and more effective than unconstrained inversion. The induced electromotive force attenuation curves of the inversion model indicate that the same attenuation curve may be used for different geological conditions. Therefore, constrained inversion using known geological information can more accurately reflect the underground geological information.
Highlights
Geophysics methods have been widely used to detect the mineral resources [1,2,3,4,5], geological structures [6,7], and urban underground space construction [8,9,10,11]
transient electromagnetic method (TEM) involves applying a current to power supply electrodes or transmitting loops, which causes it to form an electromagnetic field in the surrounding space, and
It still shows that constrained inversion is better than unconstrained inversion
Summary
Geophysics methods have been widely used to detect the mineral resources [1,2,3,4,5], geological structures [6,7], and urban underground space construction [8,9,10,11]. As one of the geophysical exploration methods, the transient electromagnetic method (TEM), on the strength of its high efficiency, is widely used in advanced detection of tunnels, accurate positioning of underground pipelines, and detection of holes underground. The commonly used processing methods are calculating apparent resistivity [12,13,14,15], drawing multi-track curves of induced electromotive force (emf) [16] and onedimensional (1D) inversion [17,18,19]. The general inversion methods without geological information are marked by slow speed, low accuracy, and multi-solvability. Compared with other inversion methods, the least squares inversion is much simpler with a high inversion speed, adopted for the study of the TEM 1D constraint inversion
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