Economic and Environmental Geology (자원환경지질)

The Korean Society of Economic and Environmental Geology (대한자원환경지질학회)
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Case Study of Fault Based on Drainage System Analysis in the Namdae Stream, Uljin Area

울진 남대천 유역의 수계분석을 통한 단층 규명 사례 연구

  • Han, Jong-Gyu (Geological Research Division, Korea Institute of Geoscience and Mineral Resources) ;
  • Choi, Sung-Ja (Geoinformatic Engineering, University of Science & Technology)
  • 한종규 (한국지질자원연구원 국토지질연구본부) ;
  • 최성자 (과학기술연합대학원대학교 지리정보시스템공학과)
  • Received : 2011.08.19
  • Accepted : 2011.10.19
  • Published : 2011.10.28
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Abstract

A DEM (digital elevation model) is produced using a digital topographic map and is now a commonly used tool in geologic surveys. This study aimed to clarify the relationship between knickpoints and faults in the Namdae stream by analyzing a DEM of the area. The Namdae drainage basin was divided into three subbasins (S1, S2 and S3) and their knickpoints developed for the middle to mid-upper regions were extracted from the DEM. The relative steepness Ks and concavity depending on the incision rate was higher in S1 than in S2 and S3 regions. We assumed that the incision rate caused by active erosion resulted from several faults crossing the basins rather than differences in rock types. There are 77 knickpoints in the Namdae drainage area, including the low-ranking branch, and 24 of thses are on the main river system (S1, S2, S3). Of these 77 knickpoints, 27 (38%) are matched by faults, and from the three basins, 13 (54%) correspond with faults, indicating that the knickpoints are connected closely with the faults. For example the average Ks (relative steepness), was 38.8, but in the overlapping area of the Samdang and Doocheon faults the Ks value was 42.99~43.39. We suggest that the faults resulted in geomorphic deformation such as the high-Ksn knickpoints. There was little evdence of relationship between the knickpoints and rock boundaries, with 54% of the knickpoints distributed on the S1, S2, and S3 subbasins. We concluded that the drainage basin knickpoints are the result of fault movement and are a type of geomorphologic deformation that could be useful for surveying Quaternary faults or fault extension.

지형정보가 전산화됨으로서 수치표고모델 및 위성영상사진 등이 지질조사에 활용되고 있다. 이 연구에서는 남대천 유역의 하천 수계 천이점을 추출하여 단층운동과의 연관성을 규명하고자 하였다. 경상북도 울진군에 위치하고 있는 남대천 유역은 S1, S2, S3 등 세 개의 소유역으로 구분되며, 수치표고모델로 추출된 천이점들은 거의 모두 소유역의 중류 및 중상류에 분포하고 있다. S1 구역에서는 하각률과 관련 있는 지형경사도 Ks와 하천 수계의 요형도 값이 S2 나 S3 보다 높은 값을 보이고 있다. 이는 삭박작용이 활발하여 하각률이 높은 것에 기인되는 것으로 암상 차에 의한 것보다는 다수의 단층에 의한 것으로 해석된다. 하위지류를 포함한 남대천 유역의 천이점은 모두 77개이며, 이 중 주요 수계 S1, S2, S3에 발달하고 있는 천이점은 24개소이다. 77개소 중 이중 단층과 일치하고 있는 천이점은 27개소 (38%)이며, 주요 수계 상에서 단층과 일치되는 천이점은 13개 지점 (54%)이다. 그러므로 주요 수계와 단층과는 밀접한 관계가 있음을 알 수 있다. 즉, 조사지역의 상대 경사도 값 Ks의 평균은 38.8이다. 그러나 두천단층과 삼당단층이 중첩되는 부분에서는 해발고도를 고려하더라고, 상대적 경사도 $K_s$은 42.99~43.39로 다른 전이점보다 매우 높은 값을 보이므로, 천이점 형성은 단층과 유관한 지형변위임을 지시한다. 또한 천이점의 분포와 지질 경계부를 비교해볼 때, 천이점은 암상 경계부와도 무관하게 발달하고 있으나, 단층분포와 연관성이 있음을 알 수 있다. 결론적으로, 수계의 천 이점 발달은 단층 운동에 의하여 형성될 수 있는 지형변위로 판단된다. 수계 분석을 통해 천이점이 단층에 의한 지형 변위로 볼 수 있으며, 제 4기 단층을 규명하거나 단층 연장을 규명할 수 있는 수단으로 활용 될 수 있다.

Keywords

Acknowledgement

Grant : 활성단층지도 및 지진위험지도 제작, 원전부지 인근신기지구조 및 해안단구 검증조사연구

Supported by : 한국지질자원연구원

References

  1. Lee, C.H., Kim, Y.J. and Choi, B.R. (1993) Korea geological map(1:50,000), Explanatory text of the geological map of Chukpyon and Imwonjin sheet, KIGAM(Korea Institute of Geoscience & Mineral Resources), p38.
  2. KHNP(Korea hydro & Nuclear Power Co. Ltd.) (2008) Preliminary Safety Analysis Report (PSAR) for New Unit 1 and 2 at Uljin.
  3. Burbank, D.W. and Anderson, R.S. (2001) Tectonic Geomorphology. Blkackwell Science, 274p.
  4. Brocklehurst, S.H. and Whipple, K.X. (2002) Glacial erosion and relief production in the Eastern Sierra Nevada, California: Geomorphology, v.42, p.1-24. https://doi.org/10.1016/S0169-555X(01)00069-1
  5. Crosby, B.T. and Whipple, K.X. (2006) Kickpoint initiation and distribution within fluvial networks: 236 waterfalls in the Waipaoa Rivier, North Island, New Zealand: Geomorphology, v.82, p.16-38. https://doi.org/10.1016/j.geomorph.2005.08.023
  6. Duvall, A., Kirby, E. and Burbank, D. (2004) Tectonic and lithologic controls on bedrock channel profiles and processes in coastal California: Journal of Geophysical Research, v.109, n.f03002, doi:10.1029/2003JF000086.
  7. Flint, J.J. (1974) Stream gradient as a function of order, magnitude, and discharge: Water resources Research, v.10, n.5, p.969-973. https://doi.org/10.1029/WR010i005p00969
  8. Hack, J.T. (1973) Stream profile analysis and stream-gradient index: U.S. Geological Survey Journal of Research, v.1, n.4, p.421-429.
  9. Hayakawa, Y.S. and Oguchi, T. (2006) DEM-based identification of knickzones and its application to Japanese mountain rivers: Geomorphology, v.78, p.90-106. https://doi.org/10.1016/j.geomorph.2006.01.018
  10. Horton, R.E. (1945) Erosional development of streams and their drainage basin: hydro-physical approach to quantitative morphology: Geological Society of America Bulletin, v.56, n.3, p.275-370. https://doi.org/10.1130/0016-7606(1945)56[275:EDOSAT]2.0.CO;2
  11. Howard, A.D. and Kerby, G. (1983) Channel changes in badlands: Geological Society of America Bulletin, v.94, p.739-752, doi: 10.1130/00167606(1983)94<739:CCIB >2.0.CO;2.
  12. Keller A.E. and Pinter N. (1996) Active Tectonics-Earthquakes, Uplift, and Landscape. Prentice Hall, New Jersey, 338p.
  13. Kirby, E. and Whipple, K.X. (2001) Quantifying differential rock-uplift rates via stream profile analysis: Geology, v.29, n.5, p.415-418. https://doi.org/10.1130/0091-7613(2001)029<0415:QDRURV>2.0.CO;2
  14. Kirby, E., Whipple, K.X., Tang, W. and Chen, Z. (2003) Distribution of active rock uplift along the eastern margin of the Tibetan Plateau: Inferences from bedrock channel longitudinal profiles: Journal of Geophysical Research, v.108, n.B4.
  15. Lee, C.S. and Tsai, L.L (2010) A quantitative analysis for geomorphic indices of longitudinal river profile: a case study of the Choushui River, central Taiwan: Environmental Earth Science, v.59, p.1549-1558. https://doi.org/10.1007/s12665-009-0140-3
  16. Rantitsch, G., Pischinger, G. and Kurz, W. (2009) Stream profile analysis of the Koralm Range (Eastern Alps): Swiss Journal of Geoscience, v.102, p.31-41. https://doi.org/10.1007/s00015-009-1305-5
  17. Snyder, N.P., Whipple, K.X, Tucker, G.E. and Merritts, D.J. (2000) Landscape response to tectonic forcing: DEM analysis of stream profiles in the Mendocino triple junction region, northern California: Geological Society of America Bulletin, v.112, n.8, p.1250-1263. https://doi.org/10.1130/0016-7606(2000)112<1250:LRTTFD>2.0.CO;2
  18. Strahler, A.N (1952) Hypsometric (area-altitude) analysis of erosional topography: Geological Society of America Bulletin, v.63, n.11, p.1117-1142. https://doi.org/10.1130/0016-7606(1952)63[1117:HAAOET]2.0.CO;2
  19. Strahler, A.N. (1957) Quantitative analysis of watershed geomorphology: Transactions of the American Geophysical Union, v.8, n.6, p.913-920.
  20. The Research Group for Active Faults of Japan (RGAF) (1991) Maps of Active Faults in Japn with an Explanatory Text. University of Tokyo Press, 437p.
  21. Whipple, K.X. and Tucker, G.E. (1999) Dynamics of the stream-power river incision model: Implications for height limits of mountain ranges, landscape response timescales, and research needs: Journal of Geophysical Research, v.104, n.b8, p.17,661-17,674. https://doi.org/10.1029/1999JB900120
  22. Wobus, C.W., Hodges, K.V. and Whipple, K.X (2003) Has focused denudation sustained active thrusting at the Himalayan topographic front?: Geology, v.31, p.861- 864. https://doi.org/10.1130/G19730.1
  23. Wobus, C., Whipple, K.X., Kirby, E., Snyder, N., Johnson, J., Spyropolou, K., Crosby, B. and Sheehan, D. (2006) Tectonics from topography: Procedures, promise, and pitfalls, in Willett, S.D., Hovius, N., Brandon, M.T., and Fisher, D.M., eds., Tectonics, Climate, and Landscape Evolution: Geological Society of America Special Paper 398, Penrose Conference Series, p.55-74.