3D finite-difference modeling algorithm and anomaly features of ZTEM
Wang Tao1, Tan Han-Dong1, Li Zhi-Qiang1, Wang Kun-Peng1, Hu Zhi-Ming1, and Zhang Xing-Dong1
1. Key Laboratory of Geo-detection Ministry of Education and School of Geophysics and Information Technology, China University of Geosciences, Beijing 100083, China.
Abstract：
The Z-Axis tipper electromagnetic (ZTEM) technique is based on a frequency-domain airborne electromagnetic system that measures the natural magnetic field. A survey area was divided into several blocks by using the Maxwell’s equations, and the magnetic components at the center of each edge of the grid cell are evaluated by applying the staggered-grid finite-difference method. The tipper and its divergence are derived to complete the 3D ZTEM forward modeling algorithm. A synthetic model is then used to compare the responses with those of 2D finite-element forward modeling to verify the accuracy of the algorithm. ZTEM offers high horizontal resolution to both simple and complex distributions of conductivity. This work is the theoretical foundation for the interpretation of ZTEM data and the study of 3D ZTEM inversion.
. 3D finite-difference modeling algorithm and anomaly features of ZTEM[J]. APPLIED GEOPHYSICS, 2016, 13(3): 553-560.
[1]
Chen, Q. L., Hu, W. B., Li, J. M., and Yan, L. J., 2007, Characteristics of tipper response of buried sphere: Journal of Oil and Gas Technology (in Chinese), 29(3), 75−78.
[2]
Farquharson, C. G., Oldenburg, D. W., and Haber, E., 2002, An algorithm for the three-dimensional inversion of magnetotelluric data: In Proceedings of the 72nd Annual International Meeting, SEG, Expanded Abstracts, 649−652.
[3]
Holtham, E., and Oldenburg, D. W., 2010a, Three-dimensional inversion of ZTEM data: Geophysical Journal International, 182, 168−182.
[4]
Holtham, E., and Oldenburg, D. W., 2010b, Three-dimensional inversion of MT and ZTEM data: 80th Annual International Meeting, SEG, Expanded Abstracts, 655−659.
[5]
Hu, W. B., Su, Z. L., Chen, Q. L., Yan, L. J., and Zheng, R. S., 1997, Character of tipper data and application: Oil Geophysical Prospecting (in Chinese), 32(2), 202−213.
[6]
Labson, V. F., Becker, A., Morrison, H. F., and Conti, U., 1985, Geophysical exploration with audio-frequency natural magnetic fields: Geophysics, 50(4), 656−664.
[7]
Lin, C. H., Tan, H. D., and Tong, T., 2008, Three dimensional conjugate gradient inversion of magnetotelluric sounding data, Applied Geophysics, 5(4), 314−321.
[8]
Lin, C. H., Tan, H. D., and Tong, T., 2011a, Three-dimensional conjugate gradient inversion of tipper data: Chinese Journal of Geophysics, 54(4), 1106−1113.
[9]
Lin, C. H., Tan, H. D., and Tong, T., 2011b, Three-dimensional conjugate gradient inversion of magnetotelluric full information data: Applied Geophysics, 8(1), 1−10.
[10]
Lo, B., and Zang, M., 2008, Numerical modeling of ZTEM (airborne AFMAG) responses to guide exploration strategies: 78th Annual International Meeting, SEG, Expanded Abstracts, 27(1), 1098−1102.
[11]
Mackie, R. L., Madden, T. R., and Wannamaker, P. E., 1993, Three-dimensional magnetotelluric modeling using difference equations-Theory and comparisons to integral equation solutions: Geophysics, 58(2), 215−226
[12]
Mackie, R. L., Smith, J. T., and Madden, T. R., 1994, Three-dimensional electromagnetic modeling using finite difference equations: The magnetotelluric example: Radio Science, 29(4), 923−935.
[13]
Sattel, D., and Witherly, K., 2012, The modeling of ZTEM data with 2D and 3D algorithms: 82th Ann International Meeting, SEG, Expanded Abstracts, 1−5.
[14]
Tan, H. D., Wei, W. B., Deng, M, and Jin, S., 2004, General use formula in MT tensor impedance: Oil Geophysical Prospecting (in Chinese), 39(1), 114−116.
[15]
Tan, H. D., Yu, Q. F., Booker J., and Wei, W. B., 2003, Magnetotelluric three-dimensional modeling using the staggered-grid finite difference method: Chinese Journal of Geophysics (in Chinese), 46(5), 705−711.
[16]
Tong, X. Z., Liu, J. X., Liu, Y., Gan, J. X., and Zhang, L.W., 2011, Calculating tipper response in two-dimensional magnetotelluric using finite element method. Journal of Jilin University (Earth Science Edition) (in Chinese), 42(Sup.1), 349−354.
[17]
Vozoff, K., 1972, The magnetotelluric method in the exploration of sedimentary basins: Geophysics, 37(1), 98−141.
[18]
Wang, W. P., and Wang, S. T., 2011, Frequency-domain aero-electromagnetic method and its application: Geology Press, Beijing, 2−6.
[19]
Ward, S. H., 1959, AFMAG-airborne and ground: Geophysics, 24(4), 761−789.
[20]
Yu, N., Hu, X. Y., Wang, X. B., and Li, J., 2014, Two-dimensional magnetotelluric tipper and apparent tipper: simulation and application: Journal of Southwest Jiaotong University (in Chinese), 49(2), 268−275.
2016, Vol. 13 
