Analysis of Magnetotelluric Response Functions at the Cam Thuy Site, Northern Vietnam

Мұқаба

Дәйексөз келтіру

Толық мәтін

Ашық рұқсат Ашық рұқсат
Рұқсат жабық Рұқсат берілді
Рұқсат жабық Рұқсат ақылы немесе тек жазылушылар үшін

Аннотация

During magnetotelluric studies in North Vietnam, an effect where the impedance phases Zxy and Zyx simultaneously left their quadrants was detected at one of the sounding sites, CTH, in the Cam Thuy District, Thanh Hoa Province. Investigation of this phenomenon has shown that it is accompanied by negative (bottom-up directed) components of the Umov–Poynting vector of electromagnetic energy flux density in the entire range of the recorded periods of magnetotelluric variations. This direction of the energy flux remains unchanged when the initial coordinate system is rotated by angles of 45° and 60°. Another characteristic feature of this phenomenon is an unusual behavior of the apparent resistivity curves: the apparent resistivity values increase starting from a period of 200 s up to a period of 104 s, and this increase occurs practically along the asymptote. The analysis of the polarization of the magnetotelluric field and the asymmetry parameter (skew angle) β of the phase tensor has shown that the section exhibits significant three-dimensional distortions as manifested by β values ranging from 20° to 90°.

Толық мәтін

Рұқсат жабық

Авторлар туралы

S. Starzhinskii

V.I. Il’ichev Pacific Oceanological Institute, Far Eastern Branch, Russian Academy of Sciences

Хат алмасуға жауапты Автор.
Email: ss_stars@poi.dvo.ru
Ресей, Vladivostok

Әдебиет тізімі

  1. Алексеев Д.А., Пальшин Н.А., Варенцов Ив. М. Дисперсионные магнитотеллурические соотношения в двумерной модели берегового эффекта // Физика Земли. 2009. № 2. С. 84–87.
  2. Бердичевский М.Н., Дмитриев В.И. Модели и методы магнитотеллурики. М.: Научный мир. 2009. 680 с.
  3. Голд Б., Рэйдер Ч. Цифровая обработка сигналов. М.: Советское радио. 1973. 368 с.
  4. Гольдштейн Л.Д., Зернов И.В. Электромагнитные поля и волны. М.: Советское радио. 1971. 662 с.
  5. Корн Г., Корн Т. Справочник по математике. М.: Наука. 1974. 831 с.
  6. Никифоров В.М., Варенцов И.М., Шкабарня Г.Н., Каплун В.Б., Жуковин А.Ю., Куонг Д.Х. Магнитотеллурические исследования северного Вьетнама в длиннопериодном диапазоне (10 < Т < 20 000 c) // Геология и геофизика. 2020. V. 61. № 9. С. 1266–1288.
  7. Отнес Р., Эноксон Л. Прикладной анализ временных рядов. М.: Мир. 1982. 428 с.
  8. Рабинер Л., Гоулд Б. Теория и применение цифровой обработки сигналов. М: Мир. 1978. 848 с.
  9. Старжинский С.С., Никифоров В.М. Результаты электромагнитных зондирований с помощью подводного кабеля JASC // Физика Земли. 2011. №3. С. 72–82.
  10. Caldwell T.G., Bibby H.M., Brown C. The magnetotelluric phase tensor // Geophys. J. Int. 2004. V. 158. № 2. P. 457–469. https://doi.org/10.1111/j.1365-246X.2004.02281.x
  11. Bibby H. M., Caldwell1 T. G., Brown C. Determinable and non-determinable parameters of galvanic distortion in magnetotellurics // Geophys. J. Int. 2005. V. 163. P. 915–930. doi: 10.1111/j.1365-246X.2005.02779.x
  12. Bonvalot S., Balmino G., Briais A., Kuhn M., Peyrefitte A., Vales N., Biancale R., Gabalda G., Reinquin F., Sarrailh M. World Gravity Map. Commission for the Geological Map of the World. 2012. Paris. BGI-CGMW-CNES-IRD.
  13. Duong T.N., Lai H.P., Pham N.D., Chen C.H., Dinh V.T. Relation between seismicity and active faults in Thanh Hoa province detected by local seismic network // Vietnam Journal of Earth Sciences. 2021. V. 43(2). P. 199–219. https://doi.org/10.15625/2615-9783/15931
  14. Egbert G.D., Kelbert A. Computational recipes for electromagnetics inverse problems // Geophys. J. Int. 2012. V. 189. P. 251–267. doi: 10.1111/j.1365-246X.2011.05347.x
  15. Haghighi T.L, Montahaei M., Oskooi B. MT data inversion and sensitivity analysis to image electrical structure of Zagros collision zone // Journal of Applied Geophysics. 2018. V. 148. P. 23–32.
  16. Hau B.V., Kim Y, Thanh N.X., Hai T.T., Yi K. Neoproterozoic deposition and Triassic metamorphism of metasedimentary rocks in the Nam Co Complex, Song Ma Suture Zone, NW Vietnam // Geosciences Journal. 2018. V. 22. № 4. P. 549–568. http://dx.doi.org/10.1007/s12303-018-0026-z
  17. Heise W., Pous J. Anomalous phases exceeding 90° in magnetotellurics: anisotropic
  18. model studies and a field example // Geophys. J. Int. 2003. V. 155. № 1. P. 308–318. https://doi.org/10.1046/j.1365-246X.2003.02050.x
  19. Key K., Constable S. Coast effect distortion of marine magnetotelluric data: Insights from a pilot study offshore northeastern Japan // Physics of the Earth and Planetary Interiors. 2011. V. 184. P. 194–207.
  20. Liddell M., Unsworth M., Pek J. Magnetotelluric imaging of anisotropic crust near Fort McMurray, Alberta: implications for engineered geothermal system development // Geophys. J. Int. 2016. V. 205. P. 1365–1381. https://doi.org/10.1093/gji/ggw089
  21. Lilley F.E.M., Weaver J.T. Phases greater then 90° in MT data: Analysis using dimensionality tools // Journal of Applied Geophysics. 2010. V. 70. P. 9–16. doi: 10.1016/J.JAPPGEO.2009.08.007
  22. Lezaeta P., Haak V. Beyond magnetotelluric decomposition: Induction, current channeling, and magnetotelluric phases over 90° // Journ. Geoph. Res. 2003. V. 186 (B6). № 36. 2305. https://doi.org/10.1029/2001JB000990
  23. Piña-Varas P., Dentith M. Magnetotelluric data from the Southeastern Capricorn Orogen, Western Australia: an example of widespread out-of-quadrant phase responses associated with strong 3-D resistivity contrasts // Geophys. J. Int. 2018. V. 212, Issue 2. P.1022–1032. https://doi.org/10.1093/gji/ggx459
  24. Selway K., Thiel S. Key K. A simple 2-D explanation for negative phases in TE magnetotelluric data // Geophys. J. Int. 2012. V. 188. P. 945–958. doi.org/10.1111/j.1365-246X.2011.05312.x
  25. Shao G., Xiao Q. Model for phase rolling out of quadrant magnetotelluric data – an example from north to the Hexi corridor [J] // Progress in Geophysics (in Chinese). 2016. V. 31. № 4. P. 1480–1491. doi: 10.6038/pg20160410
  26. Su C.-M., Wen S., Tang C.-C., Yeh Y.-L., Chau-Huei Chen C.-H. The variation of crustal structure along the Song Ma Shear Zone, Northern Vietnam // Tectonophysics. 2018. V. 734–735. P. 119–129. https://doi.org/10.1016/j.tecto.2018.04.005
  27. Vadoodi R., Rasmussen T.M., Smirnov M., Bauer B. Towards an understanding of mineral systems – Contributions from magnetotelluric data from the Fennoscandian Shield in northern Sweden // Tectonophysics. 2021. V. 808. Art. 228816
  28. Vozoff K. The magnetotelluric method in the exploration of sedimentary basins // Geophysics. 1972. V. 37. P. 98–141.
  29. Wang S., Constable S., Reyes-Ortega V., Rychert C.A. A newly distinguished marine magnetotelluric coast effect sensitive to the lithosphere–asthenosphere boundary // Geophys. J. Int. 2019. V. 218. P. 978–987 doi: 10.1093/gji/ggz202
  30. Wen S., Yeh Y.-L., Tang C.-C., Phong L.H., Toan D.V., Chen C.-H. The tectonic structure of the Song MA fault zone, Vietnam // Journal of Asian Earth Sciences. 2015. V. 107. P. 26–34. http://dx.doi.org/10.1016/j.jseas.2015.03.046
  31. Worzewski T, Jegen M., Swidinsky A. Approximations for the 2-D coast effect on marine magnetotelluric data // Geophys. J. Int. 2012. V. 189. P. 357–368. doi: 10.1111/j.1365-246X.2012.5385.x
  32. Yu G., Xiao Q., Li M. Anisotropic model study for the phase roll out of quadrant data in magnetotellurics: with examples of upper-lower structure // Chinese Journal of Geophysics (in Chinese). 2019. V. 62. № 2. P. 763–778. doi: 10.6038/cjg2019L0661
  33. Zhang R.Y., Lo C.-H., Chung S.-L. Grove M, Omori S., Iizuka Y., Liou J.G., Tri T.V. Origin and Tectonic Implication of Ophiolite and Eclogite in the Song Ma Suture Zone between the South China and Indochina Blocks // J. metamorphic Geol. 2013. V. 31. P. 49–62. doi: 10.1111/jmg.12012
  34. Zorin N., Aleksanova E., Shimizu H., Yakovlev D. Validity of the dispersion relations in magnetotellurics: Part I – theory // Earth, Planets and Space. 2020а. V. 72. https://doi.org/10.1186/s40623-020-1133-4
  35. Zorin N., Alekseev D., Epishkin D., Shimizu H., Denis Yakovlev D., Zaytsev S. Validity of the dispersion relations in magnetotellurics. Part II: synthetic and field data // Earth, Planets and Space. 2020б. V. 72.139. https://doi.org/10.1186/s40623-020-01273-4

Қосымша файлдар

Қосымша файлдар
Әрекет
1. JATS XML
Жүктеу
2. Fig. 1. Tectonic structure of the study area superimposed on the map of global gravity field model anomalies in the Bouguer WGM2012 reduction according to [Bonvalot et al., 2012] and the position of the CTH measurement point. Thick black lines show regional faults, thin lines show local faults. Blue lines outline the depths in km (blue numbers) to the crystalline basement according to the interpretation of the regional gravity field by [Duong et al., 2021]. The dotted line passing through the measurement point indicates the preferential direction of the electric field.

Жүктеу (1MB)
Метадеректер
3. Fig. 2. Polarization of electric (black line) and magnetic field variations (gray line) at the CTH site after bandpass filtering with passbands of 10-40 s (a) and 10-1000 s (b).

Жүктеу (291KB)
Метадеректер
4. Fig. 3. Amplitude (a) and phase (b) curves of apparent impedance at the CTH point obtained by processing MT variations and their standard deviations. The numbers in the graph (b) number the phase quadrants.

Жүктеу (397KB)
Метадеректер
5. Fig. 4. Interpretation parameters of the phase tensor at the CTH point: (a) - asymmetry of the phase tensor; (b) - orientation of the major axis of the phase tensor ellipse; (c) - ellipticity of the phase tensor ellipse.

Жүктеу (256KB)
Метадеректер
6. Fig. 5. Vertical component of the average energy flux in the spectral domain after bandpass filtering of the original implementation with a filter bandwidth of 5-1000 s.

Жүктеу (223KB)
Метадеректер

© Russian Academy of Sciences, 2024