Economic and Environmental Geology (자원환경지질)

The Korean Society of Economic and Environmental Geology (대한자원환경지질학회)
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A Study on the Geophysical Characteristics and Geological Structure of the Northeastern Part of the Ulleung Basin in the East Sea

동해 울릉분지 북동부지역의 지구물리학적 특성 및 지구조 연구

  • Kim, Chang-Hwan (Dokdo research center, East Sea Research Institute, Korea Ocean Research and Development Institute) ;
  • Park, Chan-Hong (East Sea Research Institute, Korea Ocean Research and Development Institute)
  • 김창환 (한국해양연구원 동해연구소 독도전문연구센터) ;
  • 박찬홍 (한국해양연구원 동해연구소)
  • Received : 2010.09.27
  • Accepted : 2010.12.14
  • Published : 2010.12.28
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Abstract

The geophysical characteristics and geological structure of the northeastern part of the Ulleung Basin were investigated from interpretation of geophysical data including gravity, magnetic, bathymetry data, and seismic data. Relative correction was applied to reduce errors between sets of gravity and magnetic data, obtained at different times and by different equipments. The northeastern margin of the Ulleung Basin is characterized by complicated morphology consisting of volcanic islands (Ulleungdo and Dokdo), the Dokdo seamounts, and a deep pathway (Korea Gap) with the maximum depth of -2500 m. Free-air anomalies generally reflect the topography effect. There are high anomalies over the volcanic islands and the Dokdo seamounts. Except local anomalous zones of volcanic edifices, the gradual increasing of the Bouguer anomalies from the Oki Bank toward the Ulleung Basin and the Korea Gap is related to higher mantle level and denser crust in the central of the Ulleung Basin. Complicated magnetic anomalies in the study area occur over volcanic islands and seamounts. The power spectrum analysis of the Bouguer anomalies indicates that the depth to the averaged Moho discontinuity is -16.1 km. The inversion of the Bouguer anomaly shows that the Moho depth under the Korea Gap is about -16~17 km and the Moho depths towards the Oki Bank and the northwestern part of Ulleung Island are gradually deeper. The inversion result suggests that the crust of the Ulleung Basin is thicker than normal oceanic crusts. The result of 20 gravity modeling is in good agreement with the results of the power spectrum analysis and the inversion of the Bouguer anomaly. Except the volcanic edifices, the main pattern of magnetization distribution shows lineation in NE-SW. The inversion results, the 2D gravity modeling, and the magnetization distribution support possible NE-SW spreading of the Ulleung Basin proposed by other papers.

본 연구에서는 울릉분지 북동부지역에서 획득한 중력, 자력, 수심자료 등 지구물리자료를 이용하여 이 지역의 지구물리학적 특성 및 지구조를 고찰하고자 하였다. 각각의 자료는 조사기간 및 사용 장비의 차이로 인하여 자료간의 오차가 나타나는데 상대적인 보정을 실시한 후 통합하였다. 울릉분지 북동부에 위치한 연구지역은 울릉도와 독도해산들, 그리고 한국해저간극으로 이루어져 있으며 최대수섬은 약 -2500 m를 보인다. 후리에어이상는 지형의 영향을 잘 반영하며 전체적으로는 울릉도와 독도 및 해산들에서 높은 값을 보인다. 부게이상은 해산들에 의한 국지적인 이상치를 보이지만 한국해저간극 및 울릉분지를 중심으로 고이상을 보이는데 이는 맨틀상승에 의한 영향이라 판단된다. 자기이상도를 살펴보면 화산체(섬과 해산들)들을 중심으로 복잡한 자기이상대를 나탄낸다. 연구지역 부게중력이상의 파워스펙트럼 분석으로부터 계산된 연구지역 모호면의 평균 깊이는 -16.1 km로 나타났다. 이 파워스펙트럼 분석을 이용하여 모호면 심도 역산을 수행하였다. 이 역산법으로 계산된 모호면의 심도는 한국해저간극지역에서 -16~17 km 정도이며 오끼뱅크 및 울릉도의 북서부쪽으로 갈수록 심도가 깊어지는 결과가 나타났다. 이 역산결과는 울릉분지의 해양지 각이 일반적인 해양지각에 비해 두껍다는 기존 결과와 일치한다. 2차원 중력 모델링 결과에서도 모호면의 심도가 해저면지진계 탐사측선이 지나가는 안용복해산과 독도 사이의 한국해저간극지역에서 얕은 것을 볼 수 있으며 오끼뱅크쪽으로 갈수록 깊어진다. 자화분포도에서는 울릉도와 독도 등 화산체에 의한 강한 자기이상대에 의해 나타나는 자화 분포대를 제외하면 주로 북동-남서방향의 선형배열이 나타난다. 섬도역산 결과, 2차원 중력모델링 및 자화분포 결과를 종합해보면 동해의 생성사 울릉분지의 가능성 있는 spreading center(해저면 확장중심) 위치가 한국해저간극에서부터 울릉분지까지 북동-남서 방향일 것이라는 기존 논문들의 주장과 부합된다고 판단된다.

Keywords

References

  1. Hayashida, A., Fukui, T. and Torii, M. (1991) Paleomagnetism of the Early Miocene Kani Group in Southwest Japan and its implication for the opening of the Japan Sea. Geophys. Res. Lett., v.18, p.1095-1098. https://doi.org/10.1029/91GL01349
  2. Hirata, N., Tokuyama, H. and Chung, T. (1989) An anomalously Thick Layering of the Crust of the Yamato Basin, Southeastern Sea of Japan : the Final Stage of Back-arc Spreading. In : G.G.R.Buchbinder, J. Ansorge & S. Crampin(Convenors), Fine Structure and Anistropy of the Lithosphere. Tectonophysics, v.165, p.304-314.
  3. Hsu, S.K., Sibuet, J.C. and Shyu, C.T. (1996) High-resolution detection of geologic boundaries from potential- field anomalies: An enhanced analytic signal technique. Geophysics, v.61, p.373-386. https://doi.org/10.1190/1.1443966
  4. Isezaki, N. and Uyeda, S. (1973) Geomagnetic Anomaly Pattern of the Japan Sea. Mar. Geophys. Res., v.2, p.51-59. https://doi.org/10.1007/BF00451870
  5. Jeon, J.S. (1995) A geophysical study on the geological structure of the southern part of the Gyeongsang Basin. Ph. D. Thesis, Univ. Yonsei, p.1-139.
  6. Jolivet, L. and Tamaki, K. (1992) Neogene Kinematics in the Japan Sea Region & Volcanic Activity of the Northeast Japan Arc. Proceedings of the Ocean Drilling Program, Science Result, 127/128(part 2), p.1311-1331.
  7. Jolivet, L., Huchon, P., Lepichon, X., Chamot-Rooke, N. and Thomas, J.C. (1991) Arc Deformation and Marginal Basin Opening: Japan Sea as a Case Study. J. Geophys. Res., v.96, p.4367-4384. https://doi.org/10.1029/90JB02455
  8. Kang, M.H., Han, H.C., Yun, H.S. and Lee, C.W. (2002) Geophysical charateristics of seamounts around Dok Island. The Sea, v.7, p.267-285.
  9. Kato, H., Isezaki, N., Park, C.H., Kim, C.H. and Nakanishi, M. (2007) Characteristics of crustal magnetic structures in the Tsushima (Ulleung) and Japan Basins from vector magnetic anomalies. Earth Planets and Space, v.59, p.887-895. https://doi.org/10.1186/BF03352751
  10. Kim, C.H. (2006) A study on Dokdo and adjacent seamounts in the northeastern part of the Ulleung Basin using geophysical data. Ph. D. Thesis, Univ. Yonsei, p.1-147
  11. Kim, C.H., Park, C.H., Ko, Y.T., Jung, E.Y., Kwak, J.Y., Yoo, S.H. and Min, K.D. (2007) The Study of Formation for Dokdo Seamounts at the Northeastern Part of the Ulleung Basin Using Gravity and Magnetic Data. Econ. Environ. Geol. Korea, v.40, p.153-170.
  12. Kim, C.H., Park, C.H., Jeong, E.Y., Ko, Y.T., Hwang, J.S. and Shim, T.M. (2009a) Flexural isostasy and loading sequence of the Dokdo seamounts on the Ulleung Basin in the East Sea (Sea of Japan). J. Asian Earth Sci., v.35, p.459-468. https://doi.org/10.1016/j.jseaes.2009.02.009
  13. Kim, C.H., Park, C.H., Jeong, E.Y., Hwang, J.S. and Ko, Y.T. (2009b) Evolution of the Dok Do seamounts, Ulleung Basin, East Sea: constraints based on reconstruction of virtual geomagnetic poles using paleomagnetic data. Geo-Mar. Lett., v.29, p.161-169. https://doi.org/10.1007/s00367-008-0131-5
  14. Kim, H.J., Han, S.J., Lee, G.H. and Huh, S. (1998) Seismic study of the Ulleung Basin crust and its implication for the opening of the East Sea (Japan Sea), Mar. Geophys. Res., v.20, p.219-237. https://doi.org/10.1023/A:1004573816915
  15. Kim, H.J, Lee, G.H., Jou, H.T., Cho, H.M., Yoo, H.S., Park, G.T. and Kim, J.S. (2007) Evolution of the eastern margin of Korea: Constraints on the opening of the East Sea (Japan Sea). Tectonophysics, v.436, p.37-55. https://doi.org/10.1016/j.tecto.2007.02.014
  16. Kim, H.J., Park, C.H., Hong, J.K., Jou, H.T., Chung, T.W., Zhigulef, V. and Anosov, G.I. (1994) A seismic experiment in the Ulleung Basin (Tsushima Basin), southwestern Japan Sea (East Sea of Korea). Geophys. Res. Lett., v.21, p.1975-1978. https://doi.org/10.1029/94GL01596
  17. Kim, K.H. (2000) K-Ar ages and Nd-Sr isotopes of Dokdo alkali volcanic rocks in the East Sea, South Korea. J. Geol. Soc. Korea, v.36, p.313-324.
  18. Kim, W.K., Kim, C.H., Park, C.H., Han, H.C., Kwon, M.S., Min, K.D., Kim, B.S. and Choi, Y.S. (2000) Structural Implications of Gravity Anomalies around Dok Island and its Surrounding Seamounts in the East Sea. Econ. Environ. Geol. Korea, v.33, p.537-545.
  19. Kim, Y.K., Lee, D.S. and Lee, K.H. (1987) Fractional Crystallizaion of the Volcanic Rocks from Dog Island, Korea. J. Geol. Soc. Korea, v.23, p.67-82.
  20. Kurashimo, E., Shinohara, M., Suyehiro, K., Kasahara, J. and Hirata, N. (1996) Seismic evidence for stretched continental crust in the Japan Sea. Geophys. Res. Lett., v.23, p.3067-3070. https://doi.org/10.1029/96GL02765
  21. Lallemand, S. and Jolivet, L., (1986) Japan Sea: a pullapart basin?. Earth Planet. Sci. Lett., v.76, p.375-389. https://doi.org/10.1016/0012-821X(86)90088-9
  22. Lee, G.H., Kim, H.J., Han, S.J. and Kim, D.C. (2001) Seismic stratigraphy of the deep Ulleung Basin in the East Sea (Japan Sea) back-arc basin. Mar. Petrol. Geol., v.18, p.615-634. https://doi.org/10.1016/S0264-8172(01)00016-2
  23. Lee, G.H., Kim, H.J., Suh, M.C. and Hong, J.K. (1999) Crustal Structure, Vol canism and Opening mode of the Ulleung Basin, East Sea(Sea of Japan). Tectonophy., v.308, p.503-525. https://doi.org/10.1016/S0040-1951(99)00113-4
  24. Min, K.D., Seo, J.H. and Kwon, B.D. (1987) Applied Geophysics. Usung Co., p.21-219.
  25. Nabighian, N.M. (1972) The analytic signal of two-dimensional magnetic bodies with polygonal cross-section: Its properties and use for automated anomaly interpretation. Geophysics, v.37, p.507-517. https://doi.org/10.1190/1.1440276
  26. Nabighian, N.M. (1974) Additional comments on the analytic signal of two-dimensional magnetic bodies with polygonal cross-section. Geophysics, v.39, p.85-92. https://doi.org/10.1190/1.1440416
  27. Otofuji, Y. and Matsuda, T. (1983) Paleomagnetic Evidence for the Clockwise Rotation of Southwest Japan arc. J. Geol. Soc. Japan, v.93, p.91-105.
  28. Otofuji, Y., Matsuda, T. and Nohda, S. (1985) Opening mode of the Japan Sea inferred from the paleomagnetism of the Japan Arc. Nature, v.317, p.603-604. https://doi.org/10.1038/317603a0
  29. Park., C.H., Kim, H.J., Yang, C.S., Suk, B.C. and Isezaki, N. (1996) Crustal structure of the Ulleung Basin, the East Sea(Japan Sea), from gravity and Ocean Bottom Seismometer data. J. Geol. Soc. Korea, v.32, p.276-290.
  30. Park, C.H. (1998) Crustal structure and evolution of the Ulleung Basin in the east sea of Korea(the Japan Sea) by deep penetrating seismic refraction, reflection, and potential field data. Ph. D. Thesis, Univ. Chiba, p.10-217.
  31. Park., C.H., Isezaki, N., Seama, N., Son, H.W. and Kim, J.W. (2002) Study on Deep Crustal Structure of the Ulleung Basin, the East Sea(Japan Sea), from Separating Shallow Components of Gravity Anomalies. J. Geol. Soc. Korea, v.38, p.519-535.
  32. Parker, R.L. and Huestis, S.P. (1974) The inversion of magnetic anomalies in the presence of topography. J. Geophys. Res., v.79, p.1587-1593. https://doi.org/10.1029/JB079i011p01587
  33. Roest, W.R., Verhoef, J. and Mark, P. (1992) Magnetic interpretation using the 3-D analytic signal. Geophysics, v.37, p.116-125.
  34. Schouten, H., Tivey, M.A., Fornari, D.J. and Cochran, J.R. (1999) Central anomaly magnetization high: constraints on the volcanic construction and architecture of seismic layer 2A at a fast-spreading mid-ocean ridge, the EPR at $9^{\circ}$30'-50'N. Earth Planet. Sci. Lett., v.169, p.37-50. https://doi.org/10.1016/S0012-821X(99)00063-1
  35. Sohn, Y.K. and Park, K.H. (1994) Geology and Evolution of Tok Island. J. Geol. Soc. Korea, v.30, p.242-261.
  36. Song, W.O. et al. (2000) The study of environments and ecosystem on land and at marine surrounding Dokdo. Korea Ocean Research and Development Institute, p.385-600.
  37. Tamaki, K. (1988) Geological structure of the Japan Sea and its tectonic implications. Bull. Geol. Surv. Japan, v.39, p.269-365.
  38. Tamaki, K., Suyehiro, K., Allan, J., Ingle, J.C. and Pisciotto, K.A. (1992) Tectonic synthesis and implications of Japan Sea ODP drilling. Proceedings of the Ocean Drilling Program, Science Result, 127/128(part 2), p.1333-1348.
  39. Thurston, J.B. and Brown, R.J. (1994) Automated sourceedge location with a new variable pass-band horizontal- gradient operator. Geophysics, v.59, p.546-554. https://doi.org/10.1190/1.1443615
  40. Uyeda, S. and Miyashiro, A. (1974) Plate tectonics and the Japanese island: a synthesis, Geol. Soc. Amer. Bull., v.85, p.1159-1170. https://doi.org/10.1130/0016-7606(1974)85<1159:PTATJI>2.0.CO;2
  41. Watts, A.B. (1978) An Analysis of Isostasy in the world's ocean 1. Hawaiian-Emperor Seamount chain. J. Geophys. Res., v.83, p.5989-6004. https://doi.org/10.1029/JB083iB12p05989
  42. Won, J.K. and Lee, M.W. (1984) The Volcanism and Petrology of alkali Volcanic rocks, Ulrung Island. J. Geol. Soc. Korea, v.20, p.296-305.