Geometric and Frequency Soundings in Small-Loop Electromagnetic Surveys

소형 루프 전자탐사에서 기하학적 수직탐사와 주파수 수직탐사

  • Cho, In-Ky (Division of Geology and Geophysics, Kangwon National University) ;
  • Ahn, Kyoung-Chan (Division of Geology and Geophysics, Kangwon National University)
  • 조인기 (강원대학교 지질, 지구물리학부) ;
  • 안경찬 (강원대학교 지질, 지구물리학부)
  • Received : 2020.06.03
  • Accepted : 2020.11.09
  • Published : 2020.11.30


Small-loop EM techniques have been used in many geophysical investigations, including shallow engineering and environmental surveys. Even though geometric and frequency soundings have been widely used, there is a debate regarding the effectiveness of frequency sounding, especially when the coil spacing is small. In this study, we analyzed the effectiveness of geometric as well as frequency soundings via the one-dimensional modeling of small-loop EM surveys. The numerical results reveal that geometric sounding can effectively provide underground information. Conversely, the frequency soundings are only effective when the loop spacing is relatively large, that is, when the induction number is large. On the contrary, the frequency soundings fail to provide any information concerning the subsurface layers if the loop spacing is not large.