Economic and Environmental Geology (자원환경지질)

The Korean Society of Economic and Environmental Geology (대한자원환경지질학회)
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Displacement of Geumwang Fault around the Pungam Basin Observed by Gravity and Aeromagnetic Field Interpretation

중력장 및 자기장 해석에 따른 풍암분지 일원 금왕단층의 지구조적인 변위

  • Received : 2024.05.29
  • Accepted : 2024.07.03
  • Published : 2024.08.30
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Abstract

To analyze the tectonic movements of the Geumwang Fault and its association with development of the Pungam Basin, the distributions of the gravity field and aeromagnetic field were interpreted. The low gravity zone (LGZ) around the Geumwang Fault shows an asymmetrical distribution, indicating sinistral (left-lateral) movement with the left side of the fault moving southeastward. The observed gravity anomaly suggests a displacement of approximately 9.3 km. The aeromagnetic distribution supports this horizontal displacement with very distinct magnetic characteristics. Using Euler deconvolution, the average depth of the Geumwang Fault was calculated to be about 1,000 meters, and it is estimated that the southwest side of the Pungam Basin is approximately 700 meters deeper than the northeast side. This strongly suggests that the Geumwang Fault has moved not only in a strike-slip but also in a dip direction. Such fault movement is characteristic of a hinge fault and has contributed to the formation of the basin through fault margin sag.

금왕단층의 지구조적인 운동과 풍암분지 발달의 연관성을 분석하기 위해 지상측정 중력장 및 항공측정 자기장 분포를 해석하였다. 금왕단층 일원의 낮은 중력이상대는 비대칭적인 분포를 보이며 단층의 좌측부가 남동쪽으로 이동한 좌수향 주향이동을 지시한다. 관측된 중력이상도에서 측정한 이동 변위는 약 9.3 km 정도이다. 항공 자기장 분포는 중력장 해석에서 나타난 약 9.3 km 정도의 수평 변위를 지지하는 매우 뚜렷한 자기장 특징을 보인다. 오일러 디콘볼루션(Euler deconvolution) 방식으로 계산한 금왕단층의 평균 깊이는 약 1,000 m이며, 풍암분지 남서쪽이 북동쪽과 비교하면 약 700 m 정도 더 깊을 것으로 판단된다. 이는 금왕단층이 주향이동뿐 아니라 경사 방향으로 움직였다는 것을 강력하게 시사하며, 이와 같은 단층의 변위는 힌지단층의 특징을 나타내며 단층경계함몰(fault margin sag)에 의한 분지 형성에 기여한 것으로 판단된다.

Keywords

Acknowledgement

이 연구는 한국연구재단 개인기초연구사업(RS-2023-00250472)과 기상청 주관 연구사업(RS-2022-KM220710)의 공동 지원으로 수행되었습니다.

References

  1. Bae, H.K. and Lee, H.K. (2014) Space-time patterns of fault activity of the Keumwang Fault developed in the Jincheon-Eumseonggun, Chungcheongbuk-do. J. Geol. Soc. Korea, v.50(6), p.735-752. https://doi.org/10.14770/jgsk.2014.50.6.735 
  2. Cheong, D.K. and Kim, K.H. (1999) Basin evolution and provenance of sediments of the Cretaceous Poongam sedimentary Basin. Jour. Petro. Soc. Korea, v.7(1), p.28-34. (in Korean with English abstract) 
  3. Choi, J.M. and Lee H.K. (2020) Evolution and space-time activity patterns of the Keumwang fault at Girin-myeon, Inje-gun, Gangwon-do. J. Geol. Soc. Korea, v.56(4), p.425-452. http://dx.doi.org/10.14770/jgsk.2020.56.4.425 
  4. Choi, P.Y. and Choi, Y.S. (2007) Stress Model of the Opening of the Cretaceous Eumseong Basin, KIGAM Bulletin, v.11(4), p.3-16 
  5. Choi, S., Kim, S.W., Choi, E.K., Lee, Y.C. and Ha, S. (2021a) Gravity field Interpretation and underground structure modelling as a method of setting horizontal and vertical Zoning of a active fault core. Econ. Environ. Geol., v.54(1), p.91-103. https://doi.org/10.9719/EEG.2021.54.1.91 
  6. Choi, S., Choi, E.K., Kim, S.W. and Lee, Y.C. (2021b) Expected segmentation of the Chugaryung fault system estimated by the gravity field interpretation. Econ. Environ. Geol., v.54(6), p.743-752. https://doi.org/10.9719/EEG.2021.54.6.743 
  7. Choi, S., Kim, S.-W., Choi, E.-K., Shin, Y. and Hong, T.-K. (2022) Analysis of the Causes of Clustered Scismicity Registered in Yeoncheon, the Middle Part of the Korean Peninsula through Gravity Field Interpretation and Modeling. Econ. Environ. Geol., v.55(6), p.633-648. https://doi.org/10.9719/EEG.2022.55.6.633 
  8. Choi, S., Kim, S.W., Yoon, J.S. and Choi, E.K. (2023) Tectonic evolution of the Yangsan Fault, SE-Korea, by gravity field interpretation. Geophys. J. Int., v.235, p.297-295. https://doi.org/10.1093/gji/ggad206 
  9. Choi, S., Kim, S.W., Choi, E.K. and Shin, Y. (2024) Displacement of Dongducheon and Wangsukcheon Fault Observed by Gravity Field Interpretation. Econ. Environ. Geol., v.57(1), p.73-81. https://doi.org/10.9719/EEG.2024.57.1.73 
  10. Choi, Y.S. (1996) Structural evolution of the Cretaceous Eumseong Basin, Korea. Ph.D. thesis, Seoul National University, 158p. (in Korean with English abstract) 
  11. Hong, N.R. and Lee, H.K. (2012) Structural features and ESR dating of the Keumwang Fault at Eumseong-gun, Chungcheongbuk-do. J. Geol. Soc. Korea, v.48(6), p.473-489. (in Korean with English abstract) 
  12. Hwang, H., McWilliams, M., Son, M. and Yang, K. (2007) Tectonic Implication of A-type Granites across the Yangsan Fault, Gigye and Gyeongju Areas, Southeast Korean Peninsula. Int. Geol. Rev., v.49(12), p.1094-1102. https://doi.org/10.2747/0020-6814.49.12.1094 
  13. Korea Institute of Geoscience and Mineral Resources (KIGAM) (2014) Regional Geophysical Anomaly Mapping. GP2013-010-2014(2). (in Korean with English abstract) 
  14. Kim, K.H. and Cheong, D.K. (1999) Sedimentary facies of the Cretaceous Poongam Sedimentary Basin in Hongcheon Area, Kangwon-do, Korea. J. Geol. Soc. Korea, v.35(4), p.279-296. (in Korean with English abstract) 
  15. Kim, M.J. and Lee, H.K. (2017) Quaternary activity patterns of the Keumwang Fault in the Wonju-si area, Gangwon-do. J. Geol. Soc. Korea, v.53(1), p.79-94 https://doi.org/10.14770/jgsk.2017.53.1.79 
  16. Lee, B.J. and Kim, B.C. (2003) Geology and structural development of the Cretaceous Gongju Basin, Korea. J. Geol. Soc. Korea, v.39(2), p.161-170. (in Korean with English abstract) 
  17. Lee, B.J., Kim, D.H., Choi, H.I., Ki, W.S. and Park, K.H. (1996) Explanatory note of the Daejeon sheet, Korea Institute of Geoscience and Mineral Resources. (in Korean with English abstract) 
  18. Lee, H.K. (1998) Structural analysis of the Cretaceous Pungam Basin. J. Geol. Soc. Korea, v.34(2), p.105-121. (in Korean with English abstract) 
  19. Lee, H.K. and Kim, H.S. (2005) Comparison of structural features of the fault zone developed at different protoliths: crystalline rocks and mudrocks. J. Struct. Geol., v.27, p.2099-2112. https://doi.org/10.1016/j.jsg.2005.06.012 
  20. Mann, P. (2007) Global catalogue, classification and tectonic origins of restraining- and releasing bends on active and ancient strike-slip fault systems. Geol. Soc. London, Spec. Publ. v.290, p.13-142. https://doi.org/10.1144/SP290.2 
  21. Nagy, D. (1966) The gravitational attraction of a right rectangular prism. Geophysics, v. 31(2), p. 362-371, https://doi.org/10.1190/1.1439779 
  22. Park, Y., Rim, H., Lim, M. and Shin, Y. (2019) The Magnetic Anomaly Map of Korea, Geophysics and Geophysical Exploration. v.22(1), p.29-36. (in Korean with English abstract) 
  23. Pasteka, R., Richter, F.P., Karcol, R., Brazda, K. and Hajach, M. (2009) Regularized derivatives of potential fields and their role in semi-automated interpretation methods. Geophys. Prospect., v.57, p.507-516. https://doi.org/10.1111/j.1365-2478.2008.00780.x 
  24. Ryang, W.H., Chough, S.K., Kim, J.S. and Shon, H. (1999) Three-dimensional configuretion of a pull-apart basin from high-resolution magnetotelluric profiling: Eumsung Basin (Cretaceous), Korea. Sediment. Geol., v.129, p.101-109. https://doi.org/10.1016/S0037-0738(99)00091-3 
  25. Reid, A.B., Allsop, J.M., Granser, H., Millet, A.J. and Somerton, I.W. (1990) Magnetic interpretation in three dimensions using Euler deconvolution. Geophysics, v.55, p.80-91. https://doi.org/10.1190/1.1442774 
  26. Shin, Y. (2006) Gravity anomaly and the distribution of granitoids in the southern part of the Korean Peninsula. J. Geo. Soc. Korea, v.42(3), p.383-396 (in Korean with English abstract) 
  27. Tamura, Y. (1982) A computer program for calculating the tide generating force. Publ. Int. Latitude Obs. Mizusawa, v.16(1), p.1-19. 
  28. Thomson, D. T. (1982) EULDPH: A new technique for making computer-assisted depth estimates from magnetic data. Geophysics, v.47, p.31-37. https://doi.org/10.1190/1.1441278 
  29. Tikhonov A.N., Glasko V.B., Litvinenko O.K. and Melichov V.P (1968) Analytic continuation of a potential in the direction of disturbing masses by the regularization method. Izvestiya Physics of the Solid Earth v.12(12), p.30-48 (in Russian; English translation: 738-747) 
  30. Weon, H.J. and Lee, H.K. (2018) ESR age and characteristic features of the Keumwang Fault developed in the Ssangjeong-ri, Eumseong-gun, Chungcheongbuk-do, Korea. J. Geol. Soc. Korea, v.54(4), p.335-357. https://doi.org/10.14770/jgsk.2018.54.4.335.