In recent years, the anisotropic study has become a hot topic in the field of electromagnetics. Currently, inversion technologies of transient electromagnetic sounding data are mainly based on the case of an isotropic medium. However, the actual underground electrical structure tends to be complicated and anisotropic. It is often found that the isotropic inversion technologies do not lead to good results for field transient electromagnetic sounding data. We have developed an algorithm for calculating the transient electromagnetic response in a layered medium with azimuthal anisotropy. An occam inversion algorithm has also been implemented to invert the transient electromagnetic data induced by a grounded horizontal electric dipole in a layered medium with azimuthal anisotropy. Synthetic examples demonstrate the stability and validity of the inversion algorithm. Experimental results show different data for inverting have great influence on the inversion results.
KeywordsAzimuthal AnisotropyLayered MediumOccam InversionHorizontalelectric DipoleTransient Electromagnetic Data
Herwanger, J.V., Pain, C.C. and Binley, A. (2004) Anisotropic Resistivity Tomography. Geophysical Journal International, 158, 409-425. http://dx.doi.org/10.1111/j.1365-246X.2004.02314.x
Zhou, B., Greenhalgh, M. and Greenhalgh, S.A. (2009) 2.5-D/3-D Resistivity Modelling in Anisotropic Media Using Gaussian Quadrature Grids. Geophysical Journal International, 176, 63-80. http://dx.doi.org/10.1111/j.1365-246X.2008.03950.x
Wang, W. and Wu, X.P. (2010) Rapid Finite Element Resistivity Forward Modeling for 3D Arloitrary Anisotropic Structures. Progress in Geophysiscs, 25, 1365-1371.
Wang, W., Wu, X.P. and Spitzer, K. (2013) Three-Dimensional DC Anisotropic Resistivity Modelling Using Finite Elements on Unstructured Grids. Geophysical Journal International, 193, 734-746. http://dx.doi.org/10.1093/gji/ggs124
Abramovici, F. and Shoham, Y. (1977) Inversion of Anisotropic Magnetotelluric Data. Geophysical Journal of the Royal Astronomical Society, 50, 55-74. http://dx.doi.org/10.1111/j.1365-246X.1977.tb01324.x
Osella, A.M. and Martinelli, P. (1993) Magnetotelluric Response of Anisotropic 2D Structures. Geophysical Journal International, 115, 819-828. http://dx.doi.org/10.1111/j.1365-246X.1993.tb01494.x
Pek, J. and Verner, T. (1997) Finite-Difference Modelling of Magnetotelluric Fields in Two-Dimensional Anisotropic Media. Geophysical Journal International, 128, 505-521. http://dx.doi.org/10.1111/j.1365-246X.1997.tb05314.x
Li, Y.G. (2002) A Finite-Element Algorithm for Electromagnetic Induction in Two-Dimensional Anisotropic Conductivity Structures. Geophysical Journal International, 148, 389-401. http://dx.doi.org/10.1046/j.1365-246x.2002.01570.x
Pek, J. and. Santos, F.A.M. (2006) Magnetotelluric Inversion for Anisotropic Conductivities in Layered Media. Physics of the Earth and Planetary Interior, 158, 139-158. http://dx.doi.org/10.1016/j.pepi.2006.03.023
Qin, L.J., Yang, C.F. and Sun, C.C. (2012) A Magnetotelluric Inversion Method of the Whole Tensor Impedance Response to One-Dimensional Anisotropic Structure. Chinese Journal of Geophysics, 55, 693-701. (In Chinese)
Montahaei, M. and Oskooi, B. (2014) Magnetotelluric Inversion for Azimuthally Anisotropic Resistivities Employing Artificial Neural Networks. Acta Geophysica, 62, 12-43. http://dx.doi.org/10.2478/s11600-013-0164-7
Huo, G.P., Hu, X.Y. and Huang, Y.F. (2015) MT Modeling for Two-Dimensional Anisotropic Conductivity Structure with Topography and Examples of Comparative Analyses. Chinese Journal of Geophysics, 58, 4696-4708. (In Chinese)
Li, X.B. and Pedersen, L.B. (1991) The Electromagnetic Response of an Azimuthally Anisotropic Half-Space. Geophysics, 56, 1462-1473. http://dx.doi.org/10.1190/1.1443166
Li, X.B. and Pedersen, L.B. (1992) Controlled-Source Tensor Magnetotelluric Responses of a Layered Earth with Azimuthal Anisotropy. Geophysical Journal International, 111, 91-103. http://dx.doi.org/10.1111/j.1365-246x.1992.tb00557.x
Li, X.B., Oskooi, B. and Pedersen, L.B. (2000) Inversion of Controlled-Source Tensor Magnetotelluric Data for a Layered Earth with Azimuthal Anisotropy. Geophysics, 65, 452-464. http://dx.doi.org/10.1190/1.1444739
Yin, C. and Maurer, H.M. (2001) Electromagnetic Induction in a Layered Earth with Arbitrary Anisotropy. Geophysics, 66, 1405-1416. http://dx.doi.org/10.1190/1.1487086
Li, Y.G. and Dai, S.K. (2011) Finite Element Modelling of Marine Controlled-Source Electromagnetic Responses in Two-Dimensional Dipping Anisotropic Conductivity Structures. Geophysical Journal International, 185, 622-636. http://dx.doi.org/10.1111/j.1365-246X.2011.04974.x
Li, Y.G., Luo, M. and Pei, J.X. (2013) Adaptive Finite Element Modeling of Marine Controlled-Source Electromagnetic Fields in Two-Dimensional General Anisotropic Media. Journal of Ocean University of China, 12, 1-5. http://dx.doi.org/10.1007/s11802-013-2110-3
Cai, H.Z., Xiong, B. and Han, M. (2014) 3D Controlled-Source Electromagnetic Modeling in Anisotropic Medium Using Edge-Based Finite Element Method. Computers & Geosciences, 73, 164-176. http://dx.doi.org/10.1016/j.cageo.2014.09.008
Yin, C.C., Ben, F. and Liu, Y.H. (2014) MSCEM 3D Modeling for Arbitrarily Anisotropic Media. Chinese Journal of Geophysics, 57, 4110-4112. (In Chinese)
Yu, L., Evans, R.L. and Edwards, R.N. (1997) Transient Electromagnetic Responses in Seafloor with Triaxial Anisotropy. Geophysical Journal International, 129, 292-304. http://dx.doi.org/10.1111/j.1365-246X.1997.tb01582.x
Collins, J.L., Everett, M.E. and Johnson, B. (2006) Detection of Near-Surface Horizontal Anisotropy in a Weathered Metamorphic Schist at Llano Uplift (Texas) by Transient Electromagnetic Induction. Physics of the Earth and Planetary Interiors, 158, 159-173. http://dx.doi.org/10.1016/j.pepi.2006.05.008
Dennis, Z.R. and Cull, J.P. (2012) Transient Electromagnetic Surveys for the Measurement of Near-Surface Electrical Anisotropy. Journal of Applied Geophysics, 76, 64-73. http://dx.doi.org/10.1016/j.jappgeo.2011.10.014
Steven, C.C., Robert, L.P. and Catherine, G.C. (1987) Occam’s Inversion: A Practical Algorithm for Generating Smooth Models from Electromagnetic Sounding Data. Geophysics, 52, 289-300. http://dx.doi.org/10.1190/1.1442303
Wang, H.J. (2004) Digital Filter Algorithm of the Sine and Cosine Transform. Chinese Journal of Engineering Geophysics, 1, 329-335.
Gong, Q., Hu, X.Y. and Meng, Y.L. (2008) Linear Dimension forward Solution of CSAMT by Hankel Transformation Method. Coal Geology & Exploration, 36, 71-73.