Abstract：
Frequency-domain airborne electromagnetics is a proven geophysical exploration method. Presently, the interpretation is mainly based on resistivity–depth imaging and one-dimensional layered inversion; nevertheless, it is difficult to obtain satisfactory results for two- or three-dimensional complex earth structures using 1D methods. 3D forward modeling and inversion can be used but are hampered by computational limitations because of the large number of data. Thus, we developed a 2.5D frequency-domain airborne electromagnetic forward modeling and inversion algorithm. To eliminate the source singularities in the numerical simulations, we split the fields into primary and secondary fields. The primary fields are calculated using homogeneous or layered models with analytical solutions, and the secondary (scattered) fields are solved by the finite-element method. The linear system of equations is solved by using the large-scale sparse matrix parallel direct solver, which greatly improves the computational efficiency. The inversion algorithm was based on damping least-squares and singular value decomposition and combined the pseudo forward modeling and reciprocity principle to compute the Jacobian matrix. Synthetic and field data were used to test the effectiveness of the proposed method.
Li Wen-Ben,Zeng Zhao-Fa,Li Jing et al. 2.5D forward modeling and inversion of frequency-domain airborne electromagnetic data[J]. APPLIED GEOPHYSICS, 2016, 13(1): 37-47.
[1]
Auken, E., Chistiansen, A. V., Jacobsen, B. H., et al., 2005, Piece-wise 1D laterally constrained inversion of resistivity data: Geophysical Prospecting, 53, 497−506.
[2]
Brodie, R., and Sambridge, M., 2006, A holistic approach to inversion of frequency-domain airborne EM data: Geophysics, 71(6), G301−G312.
[3]
Brodie, R., and Sambridge, M., 2009, Holistic inversion of frequency-domain airborne electromagnetic data with minimal prior information: Exploration Geophysics, 40, 8−16.
[4]
Cai, J., Qi, Y. F., Yin, C. C., et al., 2014, Weighted Laterally-constrained inversion of frequency-domain airborne EM data: Chinese Journal of Geophysics, 57(1), 953−960.
[5]
Chen, J., and Raiche, A., 1998, Inverting AEM data using a damped eigenparameter method: Exploration Geophysics, 29, 128−132.
[6]
Cox, L. H., Wilson, G. A., and Zhdanov, M. S., 2010, 3D inversion of airborne electromagnetic data using a moving footprint: Exploration Geophysics, 41, 250−259.
[7]
Ellis, R. G., 1988, Inversion of airborne electromagnetic data: Exploration Geophysics, 29, 121−127.
[8]
Farquharson, C. G., Oldenburg, D. W., and Routh, P. S., 2003, Simultaneous 1-D inversion susceptibility and electrical conductivity: Geophysics, 68(6), 1857−1869.
[9]
Huang, H. P., and Fraser, D. C., 1996, The differential parameter method for multifrequency airborne resistivity mapping: Geophysics, 61(1), 100−109.
[10]
Huang, H. P., and Fraser, D. C., 2002, Dielectric permittivity and resistivity mapping using high frequency helicopter-borne EM data: Geophysics, 67(3), 727−738.
[11]
Huang, H. P., and Fraser, D. C., 2003, Inversion of helicopter electromagnetic data to a magnetic conductive layered earth: Geophysics, 68(4), 1211−1223.
[12]
Hu, X. Y., Peng R. H., Wu, G. J., et al., 2013, Mineral Exploration using CSAMT data: Application to Longmen region metallogenic belt, Guangdong Province, China: Geophysics, 78(3), B111−B119.
[13]
Leppin, M., 1992, Electromagnetic modeling of 3-D source over 2D inhomogeneities in the time domain: Geophysics, 57(8), 994−1003.
[14]
Li, X. K., 2011, A MPI Based Parallel Calculation Investigation on Two Dimensional Finite Element Modelling of AEM: PhD Thesis, China University of Geosciences, Beijing.
[15]
Li, W. J., 2008, Data Processing of Frequency Domain Airborne Electromagnetic Survey: PhD Thesis, China University of Geosciences, Beijing.
[16]
Liu, G. M., and Becker, A., 1992, Evaluation of terrain effects in AEM survey suing the boundary element method: Geophysics, 57(2), 272−278.
[17]
Liu, Y. H., and Yin, C. C., 2013, 3D inversion for frequency-domain HEM data: Chinese Journal of Geophysics, 56(12), 4278−4287.
[18]
Lugão, P. P., and Wannamaker, P. E., 1996, Calculating the two-dimensional magnetotelluric Jacobian in finite elements using reciprocity: Geophys. J. Int., 127, 806−810.
[19]
McGillivaray, P. R., Oldenburg, D. W., Ellis R. G., et al., 1994, Calculation of sensitivity for the frequency-domain electromagnetic problem: Geophys. J. Int., 116, 1−4.
[20]
Nabighian, M. N., 1991, Electromagnetic theory for geophysical applications Electromagnetic Methods in Applied Geophysical: Vol.1, Theory, Geological Publishing House, 164−165.
[21]
Newman, G. A., and Alumbaugh, D. L., 1995, Frequency domain modeling of airborne electromagnetic responses using staggered finite differences: Geophysical Prospecting, 43, 1021−1042.
[22]
Oldenburg, D. W., Haber, E., and Shekhtman R., 2013, Three Dimensional inversion of multisource time domain electromagnetic data: Geophysics, 78(1), 47−57.
[23]
Raiche, A., Annetts, D., and Sugeng, F., 2001, EM target response in complex hosts: Presented at ASEG 15th Geophysical Conference and Exhibition, Brisbane.
[24]
Sengpiel, K. P., 1988, Approximate inversion of airborne EM data from a multilayered ground: Geophysical Prospecting, 36(4), 446−459.
[25]
Streich, R., 2009, 3D finite-difference frequency-domain modeling of controlled-source electromagnetic data: Direct solution and optimization for high accuracy. Geophysics 74, F95-F105.
[26]
Tan, L., 2010, 2.5D numerical simulation software developing of Frequency domain AEM: MSc Thesis, China University of Geosciences, Beijing.
[27]
Tartaras, E., and Beamish, D., 2005, Laterally-constrained inversion of fixed-wing frequency-domain AEM data: Presented at 12th European Meeting of Environmental and Near Surface Geophysics, Helsinki.
[28]
Unsworth, M. J., Travis, B. J., and Chave, A. D., 1993, Electromagnetic induction by a finite electric dipole source over a 2-D earth: Geophysics, 58, 198−214.
[29]
Vallée, M. A., and Smith, R. S., 2009, Inversion of airborne time-domain electromagnetic data to a 1D structure using lateral constraints: Near Surface Geophysics, 7, 63−71.
[30]
Viezzoli, A., Auken, E., and Munday T., 2009, Spatially constrained inversion for quasi 3D modeling of airborne electromagnetic data-an application for environmental in the Lower Murray Region of South Australia: Exploration Geophysics, 40, 173−183.
[31]
Wang, W. P., Fang, Y. Y., and Zheng G. R, 2007, The exploration efficiency of the helicopter electromagnetic system in Longmen, Guangdong province: Geophysical & Geochemical exploration, 31(6), 546−550.
[32]
Wang, Y. H., 2013, The Research on HTEM 2.5D Forward Modeling and Curve Analysis: MSc Thesis, Chendu University of Technology.
[33]
Ward, S. H., and Hohmann, G. W., 1988, Electromagnetic theory for geophysical applications Electromagnetic Methods in Applied Geophysical: Vol.1, Theory, in Nabighian, M. N., Ed., Society of exploration geophysics, 131−311.
[34]
Wilson, G. A., Raiche, A. P., and Sugeng F., 2006, 2.5D inversion of airborne electromagnetic data: Exploration Geophysics, 37, 363−371.
[35]
Yin, C. C., and Hodgres, G., 2007, Simulated annealing for airborne EM inversion; Geophysics, 72(4), F189−F196.
[36]
Yin, C. C., Ren, X. Y., Liu, Y. H., et al., 2015a, Review on airborne electromagnetic inversion theory and applications, Geophysics, 80(4), W17-W31.
[37]
Yin, C. C., Zhang, B., Liu, Y. H., et al., 2015b, 2.5-D forward modeling of the time-domain airborne EM system in areas with topographic relief: Chinese J. Geophys. (in Chinese), 58(4), 1411-1424.
[38]
Yin, H. J., 2012, 2.5D forward of time-domain of airborne electromagnetic: MSc Thesis, China University of Geosciences, Beijing.
[39]
Yi, M. J., and Sasaki, Y., 2015, 2-D and 3-D joint inversion of loop-loop electromagnetic and electrical data for resistivity and magnetic susceptibility: Geophys. J. Int., 203, 1085-1095.
[40]
Zhou, D. Q., Tan, L., Tan, H. D., et al., 2010, Inversion of frequency domain helicopter-borne electromagnetic data with Marquardt’s method: Chinese Journal of Geophysics, 56(2), 421−427.
[41]
Zhou, J. J., 2011, Research on Airborne Transient Electromagnetic 2.5D Forward Modeling: MSc Thesis, Central South University.
[42]
Zienkiewicz, O. C., 1977, The Finite Element Method, third edition: McGraw-Hill.
2016, Vol. 13 
