Sea-effect Correction of 3D Magnetotelluric Responses

doi:None

All Issue

2008 Vol.45, Issue 5 Preview Page Next Page

Sea-effect Correction of 3D Magnetotelluric Responses 3차원 MT 탐사 자료의 바다효과 보정: 남명진, 한누리, 최지향, 이태종, 김희준, 송윤호
Myung Jin Nam, Nuree Han, Jihyang Choi, Tae Jong Lee, Hee Joon Kim, and Yoonho Song

31 October 2008. pp. 463-473

PDF

Abstract

In order to investigate geothermal energey resources, Korea Institute of Geoscience and Mineral Resources (KIGAM) have coducted magnetotellurics (MT) surveys for years in Pohang and Jeju, Korea. Since the survey sites are close to sea, low-frequency MT data measured in Pohang and Jeju are not free from sea effects. Subsequently, inversion of MT data may result in misinterpretation of the subsurface if sea effects are not considered properly. The sea effects can be considered in the interpretation of MT data in two different ways: incorporating sea into an earth model in inversion and compensating sea effects from MT data before conducting inversion. The first approach may suffer from numerical difficulties due to the presence of electrically conductive sea. Using the second method, we can invert distorted MT data using currently available inversion algorithms that were designed for a model without sea. This paper presents a method to compensate sea effects on MT data by correcting both electric and magnetic fields distorted by sea effects. We validate the correction scheme using synthetic models with one or two-layered hosts. Nonlinear least-squares inversion of corrected MT data successfully recovers major features of the synthetic model.

Keywords

Inversion

Sea effect

Correction

MT 탐사가 포항과 제주도 등지에서 지열에너지 개발을 위해 한국지질자원연구원의 주도 하에 최근 활발하게 진행되고 있다. MT 탐사에서는 비교적 낮은 주파수 대역을 이용하므로 포항이나 제주도와 같이 바다에 인접한 지역에서 획득한 MT 탐사 자료는 바다효과로부터 자유로울 수 없다. 따라서 MT 자료의 역산에서 이러한 바다효과를 고려하지 않는다면 역산 결과는 잘못된 해석을 초래할 가능성이 높다. 바다효과가 포함된 MT 자료를 해석하는 방법으로는 바다를 역산 과정에 포함하는 방법과 바다효과를 MT 자료에서 제거하는 방법을 생각할 수 있다. 바다를 포함하는 역산은 육지와 바다의 전기비저항의 현저한 차이로 인해 모델링의 수렴성에 관한 어려움이 있다. 이 연구에서는 MT 자료에서 바다효과를 제거하는 방법을 제시하고, 섬모델에 대해 계산한 MT 자료를 보정하여 바다효과 보정의 효용성을 확인하였다. 뿐만 아니라 바다효과를 보정한 MT 자료의 역산을 통해 지하 매질의 전기비저항 구조를 성공적으로 구현할 수 있음을 확인하였다.

키워드

3차원

역산

바다효과

보정

References

송윤호, 조인기, 김정호, 정승환, 전정수, 1992, 제주도에서의 MT 탐사, 전기, 전자탐사 연구, 연구보고서 KR-92-1G-5, 한국자원연구소, 31-69.
송윤호, 이창범, 박덕원, 김형찬, 이철우, 이성곤, 박인화, 이태종, 심병완, 조병욱, 염병우, 이승구, 기원서, 현혜자, 손정술, 황세호, 오재호, 이윤수, 박찬, 정용복, 김통권, 이진수, 고동찬, 안은영, 윤욱, 2005, 심부 지열 에너지 개발 사업, 한국지질자원연구원 기본사업 연차보고서, AA2003001-2005(3), 과학기술부, p. 147.
이춘기, 권병두, 이희순, 조인기, 오석훈, 송윤호, 이태종, 2007a, 한반도 횡단 자기지전류 탐사에 의한 상부 지각의 지전기적 구조, 한국지구과학회지, 28, No. 2, pp. 187-201. 이춘기, 이희순, 권병두, 조인기, 오석훈, 송윤호, 이태종, 2007b, 자기지전류 탐사 자료에 나타나는 옥천대의 전기적 이방성 구조, 한국지구과학회지, 28, No. 2, pp. 227-239.
이태종, 송윤호, Uchida, T., 2005a, 심부지열자원개발을위한 MT 탐사자료의2차원역산해석,물리탐사, 8, pp. 145-155.
이태종, 송윤호, Uchida, T., 2005b, 포항 지열개발 지역 MT 탐사자료의 2차원 및 3차원 해석, 한국지구시스템공학회지, 42, pp. 297-307.
Bapat, V. J., Segawa, J., Honkura, Y., and Tarits, P., 1993, “Numerical estimations of the sea effect on the distribution of induction arrows in the Japanese island arc,” Physics of the Earth Planet. Inter. and Planetary Interiors, 81, pp. 215-229.
Berdichevsky, M. N., and Dmitriev, V. I., 2002, Magnetotellurics in the context of the theory of ill-posed problems, Soc. Expl. Geophys.
Chouteau, M., and Bouchard, K., 1988, “Two-dimensional terrain correction in magnetotelluric surveys,” Geophysics, 53, pp. 854-862.
deGroot-Hedlin, C., 1991, “Removal of static shift in two dimensions by regularized inversion,” Geophysics, 56, pp. 2102-2106.
Fox, R. C., Hohmann, G. W., Killpack, T. J., and Rijo, L., 1980, “Topographic effects in resistivity and inducedpolarization surveys,” Geophysics, 45, pp. 75-93.
Goldstein, N. E., 1988, “Subregional and detailed exploration for geothermal-hydrothermal resources,” Geotherm. Sci. and Tech., 1, pp. 303-431.
Holcombe, H. T., and Jiracek, G. R., 1984, “Three-dimensional terrain corrections in resistivity surveys,” Geophysics, 49, 439-452.
Honkura, Y., Niblett, B. R., and Kurtz, R. D., 1976, “Changes in magnetic and telluric fields in a seismically active region of eastern Canada,” Tectonophysics, 34, 219-230.
Jiracek, G. R., Redding, R. P., and Kosima, R. K., 1989, “Application of the Rayleigh-FFT technique to magnetotelluric modiling and correction,” Phys. Earth. Planet. Int., 53, 365-375.
Key, K. W., Constable, S. C., and Weiss, C. J., 2004, “Mapping 3D salt using 2D marine magnetotelluric method: Case study from Gemini Prospect, Gulf of Mexico,” 74th Ann. Internat. Mtg, Soc. Expl. Geophys., Expanded Abstract, 596-599.
Lee, T. J., Song, Y. and Uchida, T., 2007, “Three-dimensional magnetotelluric surveys for geothermal development in Pohang, Korea,” Exploration Geophysics, 38, 44-49.
Loke, M. H. and Barker, R. D., 1996, “Practical technique for 3D resistivity surveys and data inversion,” Geophysical Prospecting, 44, 499-523.
Monteiro Santos, F. A., Nolasco, M., Almeida, E., Pous, J., Marcuello, A., and Queralt, P., 1999, Correction of the ocean and coast effects on the magnetotelluric impedance tensor, The 2nd Int. Sympo.: Second International Symposium on 3-D EM (3DEM-2), 309-312.
Monteiro Santos, F. A., Trota, A., Soares, A., Luzio, R., Lourenco, N., Matos, L., Almeida, E., Gaspar, J., and Miranda, J. M., 2006, “An audio-magnetotelluric investigation in Terceria Island (Azores),” Journal of Applied Geophysics, 59, 314-323.
Nam, M. J., Kim, H. J., Song, Y., Lee, T. J., Son, J. -S., and Suh, J. H., 2007, “3D magnetotelluric modeling including surface topography,” Geophysical Prospecting, 55, 277-287.
Nam, M. J., Kim, H. J., Song, Y., Lee, T. J., and Suh, J. H., 2008, “Three-dimensional topographic corrections of magnetotelluric data,” Geophysical Journal International, 174, 464-474.
Oh, S., Yang, J., Lee, D. K., Kim, S.-K., Mogi, T., Nakada, M., Song Y., 2003, “Study on deep structure of the Korean peninsula by GDS and teleseismic data,” Proceedings, 2003 Korea-Japan Joint Seminar on Geophysical Techniques for Geothermal Exploration and Subsurface Imaging, 68-76.
Orange, A. A., 1989, “Magnetotelluric exploration for hydrocarbons,” Proc. IEEE, 77, 287-317.
Sasaki, Y., 2004, “Three-dimensional inversion of static-shifted magnetotelluric data,” Earth Planets Space, 56, 239-248.
Solon, K. D., Jones, A. G., Nelson, K. D., Unsworth, M. J., Kidd, W. F., Wei, W., Tan, H., Jin, S., Deng, M., Booker, J. R., Li, S., and Bedrosian, P., 2005, “Structure of the crust in the vicinity of the Banggong-Nujiang
suture in central Tibet from INDEPTH magnetotelluric data,” J. Geophys. Res., 110, B10102.
Unsworth, M., Soyer, W., Tuncer, V., Wagner, A., and Barnes, D., 2007, “Hydrogeologic assessment of the Amchitka Island nuclear test site (Alaska) with magnetotellurics,” Geophysics, 72, No. 3, B47-B57.
Vozoff, K., 1991, The magnetotelluric method, in Misac N. Nabighian, Ed., Electromagnetic methods in applied geophysics, Soc. Expl. Geophys, Vol. II.
Wannamaker, P. E., Booker, J. R., Filloux, J. H., Jones, A. G., Jiracek, G. Rl, Chave, A. D., Tarits, P., Waff, H. S., Egbert, G. G., Young, C. T., Stodt, J. A., Martinez, M., Law, L. KL., Yukutake, T., Segawa, J. S., White, A., and Green, A., W., Jr., 1989, “Magnetotelluric observations across the Juan de Fuca subduction system in the EMSLAB project,” J. Geophys. Res., 94B10, 14111-14125.
Weidelt, P., 1972, “The inverse problem of geomagnetic induction,” J. Geophys., 38, 257-289.
Zhdanov, M. S., Wan, L., Constable, S., and Key, K., 2004, “New development in 3D marine MT modeling and inversion for off-shore petroleum exploration,” 74th Ann. Internat. Mtg, Soc. Expl. Geophys., Expanded Abstract, 588-591.
Zonge, K. L., and Hughes, L. J., 1991, Controlled Source Audio-Frequency Magnetotellurics, in Mixac N. Nabighian, Ed., Electromagnetic methods in applied geophysics, Soc. Expl. Geophys., Vol. II.

Information

Publisher :The Korean Society of Mineral and Energy Resources Engineers
Publisher(Ko) :한국자원공학회
Journal Title :Journal of the Korean Society for Geosystem Engineering
Journal Title(Ko) :한국지구시스템공학회지
Volume : 45
No :5
Pages :463-473

[1] 송윤호, 조인기, 김정호, 정승환, 전정수, 1992, 제주도에서의 MT 탐사, 전기, 전자탐사 연구, 연구보고서 KR-92-1G-5, 한국자원연구소, 31-69.

[2] 송윤호, 이창범, 박덕원, 김형찬, 이철우, 이성곤, 박인화, 이태종, 심병완, 조병욱, 염병우, 이승구, 기원서, 현혜자, 손정술, 황세호, 오재호, 이윤수, 박찬, 정용복, 김통권, 이진수, 고동찬, 안은영, 윤욱, 2005, 심부 지열 에너지 개발 사업, 한국지질자원연구원 기본사업 연차보고서, AA2003001-2005(3), 과학기술부, p. 147.

[3] 이춘기, 권병두, 이희순, 조인기, 오석훈, 송윤호, 이태종, 2007a, 한반도 횡단 자기지전류 탐사에 의한 상부 지각의 지전기적 구조, 한국지구과학회지, 28, No. 2, pp. 187-201. 이춘기, 이희순, 권병두, 조인기, 오석훈, 송윤호, 이태종, 2007b, 자기지전류 탐사 자료에 나타나는 옥천대의 전기적 이방성 구조, 한국지구과학회지, 28, No. 2, pp. 227-239.

[4] 이태종, 송윤호, Uchida, T., 2005a, 심부지열자원개발을위한 MT 탐사자료의2차원역산해석,물리탐사, 8, pp. 145-155.

[5] 이태종, 송윤호, Uchida, T., 2005b, 포항 지열개발 지역 MT 탐사자료의 2차원 및 3차원 해석, 한국지구시스템공학회지, 42, pp. 297-307.

[6] Bapat, V. J., Segawa, J., Honkura, Y., and Tarits, P., 1993, “Numerical estimations of the sea effect on the distribution of induction arrows in the Japanese island arc,” Physics of the Earth Planet. Inter. and Planetary Interiors, 81, pp. 215-229.

[7] Berdichevsky, M. N., and Dmitriev, V. I., 2002, Magnetotellurics in the context of the theory of ill-posed problems, Soc. Expl. Geophys.

[8] Chouteau, M., and Bouchard, K., 1988, “Two-dimensional terrain correction in magnetotelluric surveys,” Geophysics, 53, pp. 854-862.

[9] deGroot-Hedlin, C., 1991, “Removal of static shift in two dimensions by regularized inversion,” Geophysics, 56, pp. 2102-2106.

[10] Fox, R. C., Hohmann, G. W., Killpack, T. J., and Rijo, L., 1980, “Topographic effects in resistivity and inducedpolarization surveys,” Geophysics, 45, pp. 75-93.

[11] Goldstein, N. E., 1988, “Subregional and detailed exploration for geothermal-hydrothermal resources,” Geotherm. Sci. and Tech., 1, pp. 303-431.

[12] Holcombe, H. T., and Jiracek, G. R., 1984, “Three-dimensional terrain corrections in resistivity surveys,” Geophysics, 49, 439-452.

[13] Honkura, Y., Niblett, B. R., and Kurtz, R. D., 1976, “Changes in magnetic and telluric fields in a seismically active region of eastern Canada,” Tectonophysics, 34, 219-230.

[14] Jiracek, G. R., Redding, R. P., and Kosima, R. K., 1989, “Application of the Rayleigh-FFT technique to magnetotelluric modiling and correction,” Phys. Earth. Planet. Int., 53, 365-375.

[15] Key, K. W., Constable, S. C., and Weiss, C. J., 2004, “Mapping 3D salt using 2D marine magnetotelluric method: Case study from Gemini Prospect, Gulf of Mexico,” 74th Ann. Internat. Mtg, Soc. Expl. Geophys., Expanded Abstract, 596-599.

[16] Lee, T. J., Song, Y. and Uchida, T., 2007, “Three-dimensional magnetotelluric surveys for geothermal development in Pohang, Korea,” Exploration Geophysics, 38, 44-49.

[17] Loke, M. H. and Barker, R. D., 1996, “Practical technique for 3D resistivity surveys and data inversion,” Geophysical Prospecting, 44, 499-523.

[18] Monteiro Santos, F. A., Nolasco, M., Almeida, E., Pous, J., Marcuello, A., and Queralt, P., 1999, Correction of the ocean and coast effects on the magnetotelluric impedance tensor, The 2nd Int. Sympo.: Second International Symposium on 3-D EM (3DEM-2), 309-312.

[19] Monteiro Santos, F. A., Trota, A., Soares, A., Luzio, R., Lourenco, N., Matos, L., Almeida, E., Gaspar, J., and Miranda, J. M., 2006, “An audio-magnetotelluric investigation in Terceria Island (Azores),” Journal of Applied Geophysics, 59, 314-323.

[20] Nam, M. J., Kim, H. J., Song, Y., Lee, T. J., Son, J. -S., and Suh, J. H., 2007, “3D magnetotelluric modeling including surface topography,” Geophysical Prospecting, 55, 277-287.

[21] Nam, M. J., Kim, H. J., Song, Y., Lee, T. J., and Suh, J. H., 2008, “Three-dimensional topographic corrections of magnetotelluric data,” Geophysical Journal International, 174, 464-474.

[22] Oh, S., Yang, J., Lee, D. K., Kim, S.-K., Mogi, T., Nakada, M., Song Y., 2003, “Study on deep structure of the Korean peninsula by GDS and teleseismic data,” Proceedings, 2003 Korea-Japan Joint Seminar on Geophysical Techniques for Geothermal Exploration and Subsurface Imaging, 68-76.

[23] Orange, A. A., 1989, “Magnetotelluric exploration for hydrocarbons,” Proc. IEEE, 77, 287-317.

[24] Sasaki, Y., 2004, “Three-dimensional inversion of static-shifted magnetotelluric data,” Earth Planets Space, 56, 239-248.

[25] Solon, K. D., Jones, A. G., Nelson, K. D., Unsworth, M. J., Kidd, W. F., Wei, W., Tan, H., Jin, S., Deng, M., Booker, J. R., Li, S., and Bedrosian, P., 2005, “Structure of the crust in the vicinity of the Banggong-Nujiang

[26] suture in central Tibet from INDEPTH magnetotelluric data,” J. Geophys. Res., 110, B10102.

[27] Unsworth, M., Soyer, W., Tuncer, V., Wagner, A., and Barnes, D., 2007, “Hydrogeologic assessment of the Amchitka Island nuclear test site (Alaska) with magnetotellurics,” Geophysics, 72, No. 3, B47-B57.

[28] Vozoff, K., 1991, The magnetotelluric method, in Misac N. Nabighian, Ed., Electromagnetic methods in applied geophysics, Soc. Expl. Geophys, Vol. II.

[29] Wannamaker, P. E., Booker, J. R., Filloux, J. H., Jones, A. G., Jiracek, G. Rl, Chave, A. D., Tarits, P., Waff, H. S., Egbert, G. G., Young, C. T., Stodt, J. A., Martinez, M., Law, L. KL., Yukutake, T., Segawa, J. S., White, A., and Green, A., W., Jr., 1989, “Magnetotelluric observations across the Juan de Fuca subduction system in the EMSLAB project,” J. Geophys. Res., 94B10, 14111-14125.

[30] Weidelt, P., 1972, “The inverse problem of geomagnetic induction,” J. Geophys., 38, 257-289.

[31] Zhdanov, M. S., Wan, L., Constable, S., and Key, K., 2004, “New development in 3D marine MT modeling and inversion for off-shore petroleum exploration,” 74th Ann. Internat. Mtg, Soc. Expl. Geophys., Expanded Abstract, 588-591.

[32] Zonge, K. L., and Hughes, L. J., 1991, Controlled Source Audio-Frequency Magnetotellurics, in Mixac N. Nabighian, Ed., Electromagnetic methods in applied geophysics, Soc. Expl. Geophys., Vol. II.

Journal of the Korean Society of Mineral and Energy Resources Engineers ISSN:2288-0291(Print) 2288-2790(Online) 한국자원공학회지

All Issue