Application of Mutiple Geophysical Methods in Investigating the Lava Tunnel of Manjanggul in Cheju Island

제주도 만장굴에 대한 복합 지구물리탐사 기법의 적용

  • Kwon, Byung-Doo (Department of Earth Sciences, Seoul National University) ;
  • Lee, Heui-Soon (Department of Sciences Education, Inchon-National University of Education) ;
  • Oh, Seok-Hoon (Department of Earth Sciences, Seoul National University) ;
  • Lee, Chun-Ki (Department of Earth Sciences, Seoul National University)
  • 권병두 (서울대학교 지구과학교육과) ;
  • 이희순 (인천교육대학교 과학교육과) ;
  • 오석훈 (서울대학교 지구과학교육과) ;
  • 이춘기 (서울대학교 지구과학교육과)
  • Received : 1998.10.09
  • Accepted : 1998.11.21
  • Published : 1998.12.31


Various geophysical methods have been applied to the survey of the lava tunnel of Manjanggul in Cheju Island to study the effectiveness of each method in investigating underground tunnels. The surveys employing gravity, magnetic, electrical, AMT and VLF methods were carried out along seven profiles across the Manjanggul; especially, all the five methods were used on one representative profile. Several aspects of different methods pertinent to their use in investigation of underground tunnels have been noted. The electrical method employing the dipole-dipole array appeared to be the most effective one among five methods. Therefore, we have tested the electrical method more carefully by using various electrode spacings, and obtained successful resistivity sections showing the existence of lava tunnels. The gravity method provided relatively successful responses associated with the tunnel although the gravity readings were contaminated by wind blowing during the survey. The gravity data were also useful for the quantitative modeling study. The magnetic data were also successful in delineating the tunnel qualitatively. The AMT data were not successful because the used frequency band was not appropriate in detecting very shallow target. The VLF data were severely influenced by the neighboring noise sources such as power lines and were not successful in detecting the tunnel responses. The comprehensive result of electrical, gravity and magnetic surveys suggests that undiscovered lava tunnels may exist adjacent to the Manjanggul.



Supported by : 한국학술진흥재단