The paper is devoted to the problem of processing the airborne electromagnetic (AEM) data with a view to developing recommendations on parameterization of a geological medium for carrying out the geometric 3D-inversion of airborne data. The study is performed with the use of finite element 3D-modeling of transient EM fields induced by the helicopter AEM system in complex media followed by the 3D-inversion of airborne synthesized data. The geoelectrical models chosen for investigation are taken as typical of this class of airborne EM surveys: the rugged topography and the conductive inhomogeneous top layer, which overlaps the low-resistive layer containing target conductive bodies. It is shown that, if the variations of the top layer thickness do not exceed 30…35 m in performing 3D-inversion, as a minimum, at its first stage, the top layer can be recovered as equivalent with constant (but recovered) thickness, i.e. when the top layer is parameterized in the inverse problem, in the vector of the unknowns we can include only lateral borders of
3D-inhomogeneities, their conductivity, and layer thickness described by one parameter. It is also shown that, if, in the medium under study, the variations of the top layer thickness are more significant, its bottom border should be recovered in more detail, because otherwise the target objects located in the second layer with the responses of about 15…20 % of the measured signals can be missed, while, in the case of recovering the top layer parameters more accurately, these target objects can be discovered quite confidently.
1. Abd Allah S., Mogi T., Ito H., Jomori A., Yuuki Y., Fomenko E., Kiho K., Kaieda H., Suzuki K., Tsukuda K. Three-dimensional resistivity characterization of a coastal area: application of grounded electrical-source airborne transient electromagnetic (GREATEM) survey data from Kujukuri Beach, Japan. Journal of Applied Geophysics, 2013, vol. 99, pp. 1–11.
2. Andersen K.K., Kirkegaard C., Foged N., Christiansen A.V., Auken E. Artificial neural networks for removal of couplings in airborne transient electromagnetic data. Geophysical Prospecting, 2016, vol. 64, no. 3, pp. 741–752.
3. Dehiya R.S.A., Gupta P.K., Israil M. Interpretation of CSEM data using 2D block inversion algorithm. 22nd EM Induction Workshop, Weimar, Germany, 2014.
4. Grayver A.V. Parallel three-dimensional magnetotelluric inversion using adaptive finite-element method. Part I. Theory and synthetic study. Geophysical Journal International, 2015, vol. 202, no. 1, pp. 584–603.
5. Haber E., Schwarzbach C. Parallel inversion of large-scale airborne time-domain electromagnetic data with multiple OcTree meshes. Inverse Problems, 2014, vol. 30, no. 5.
6. Liu Y., Yin C. 3D inversion for multipulse airborne transient electromagnetic data. Geophysics, 2016, vol. 81, no. 6, pp. E401–E408.
7. McMillan M.S., Schwarzbach C., Haber E., Oldenburg D.W. 3D parametric hybrid inversion of time-domain airborne electromagnetic data. Geophysics, 2015, vol. 80, no. 6, pp. K25–K36.
8. McMillan M.S., Schwarzbach C., Haber E., Oldenburg D.W. Multiple body parametric inversion of frequency- and time-domain airborne electromagnetic. SEG Technical Program Expanded Abstracts, 2016, vol. 35, pp. 846–851.
9. Mogilatov V., Goldman M., Persova M., Soloveichik Y., Koshkina Y., Trubacheva O., Zlobinskiy A. Application of the marine circular electric dipole method in high latitude Arctic regions using drifting ice floes. Journal of Applied Geophysics, 2016, vol. 135, pp. 17–31.
10. Oldenburg D.W., Haber E., Shekhtman R. Three dimensional inversion of multisource time domain electromagnetic data. Geophysics, 2013, vol. 78, no. 1, pp. E47–E57.
11. Persova M.G., Soloveichik Y.G., Koshkina Y.I., Vagin D.V., Trubacheva O.S. Geometrical nonlinear 3D inversion of airborne time domain EM data. Near Surface Geoscience 2016: 1st Conference on Geophysics for Mineral Exploration and Mining, Barcelona, Spain, 2016.
12. Persova M.G., Soloveichik Y.G., Trigubovich G.M., Tokareva M.G. Methods and algorithms for reconstructing three-dimensional distributions of electric conductivity and polarization in the medium by finite-element 3D modeling using the data of electromagnetic sounding. Izvestiya. Physics of the Solid Earth, 2013, vol. 49, no. 3, pp. 329–343.
13. Persova M.G., Soloveichik Y.G., Trigubovich G.M., Vagin D.V., Domnikov P.A. Transient electromagnetic modelling of an isolated wire loop over a conductive medium. Geophysical Prospecting, 2014, vol. 62, no. 5, pp. 1193–1201.
14. Persova M.G., Soloveichik Y.G., Vagin D.V., Domnikov P.A., Kiselev D.S., Koshkina Y.I., Simon E.I. Multidimensional processing of the airborne EM data in the complex media. Engineering and Mining Geophysics 2018, Kazakhstan, Almaty, 2018.
15. Schenk O., G?artner K. Solving unsymmetric sparse systems of linear equations with PARDISO. Future Generation Computer Systems, 2004, vol. 20, no. 3, pp. 475–487.
16. Singh A.D.R., Gupta P.K., Israil M. Development of block inversion algorithm and its comparison with cell inversion schemes. 22nd EM Induction Workshop, Weimar, Germany, 2014.
17. Soloveichik Y.G., Persova M.G., Domnikov P.A., Koshkina Y.I., Vagin D.V. Finite-element solution to multidimensional multisource electromagnetic problems in the frequency domain using non-conforming meshes. Geophysical Journal International, 2018, vol. 212, no. 3, pp. 2159–2193.
18. Yang D., Oldenburg D.W. Three-dimensional inversion of airborne time-domain electromagnetic data with applications to a porphyry deposit. Geophysics, 2012, vol. 77, no. 2, pp. B23–B34.
19. Yang D., Oldenburg D.W., Haber E. 3-D inversion of airborne electromagnetic data parallelized and accelerated by local mesh and adaptive soundings. Geophysical Journal International, 2014, vol. 196, no. 3, pp. 1492–1507.
20. Persova M.G., Soloveichik Y.G., Vagin D.V., Kiselev D.S., Kondratyev N.V., Koshkina Y.I., Trubacheva O.S. Primenenie nekonformnykh setok s shestigrannymi yacheikami dlya 3D-modelirovaniya tekhnologii aeroelektrorazvedki [Application of non-conforming meshes with hexahedral cells for 3D modelling of airborne electromagnetic technologies]. Doklady Akademii nauk vysshei shkoly Rossiiskoi Federatsii – Proceedings of the Russian higher school Academy of sciences, 2018, no. 1 (38), pp. 64–79.
21. Persova M.G., Trubacheva O.S. O podkhode k resheniyu obratnoi zadachi vyzvannoi polyarizatsii pri vosstanovlenii granits anomal'nykh po polyarizuemosti ob"ektov [On an approach to solving induced polarization inverse problems under recovery of boundaries of an object with anomalous polarizability]. Doklady Akademii nauk vysshei shkoly Rossiiskoi Federatsii – Proceedings of the Russian higher school Academy of sciences, 2015, no. 3 (28), pp. 88–98.
22. Soloveichik Yu.G., Royak M.E., Persova M.G. Metod konechnykh elementov dlya resheniya skalyarnykh i vektornykh zadach [The finite element method for the solution of scalar and vector problems]. Novosibirsk, NSTU Publ., 2007. 896 p.
23. Soloveichik Yu.G., Tokareva M.G., Persova M.G. Reshenie trekhmernykh statsionarnykh zadach elektrorazvedki na neregulyarnykh parallelepipeidal'nykh setkakh [The solution of three-dimensional stationary problems EM survey on irregular parallelepipedal grids]. Vestnik Irkutskogo gosudarstvennogo tekhnicheskogo universiteta – Bulletin of Irkutsk State Technical University, 2004, no. 1 (17), pp. 22–33.
Kondratyev N.V., Kiselev D.S., Vagin D.V., Persova M.G., Soloveichik Yu.G. A study of equivalence of influences of varying thickness and conductivity in 3D-processing of airborne electromagnetic data in complex media. Nauchnyi vestnik Novosibirskogo gosudarstvennogo tekhnicheskogo universiteta – Science bulletin of the Novosibirsk state technical university, 2018, no. 4 (73), pp. 59–78. doi: 10.17212/1814-1196-2018-4-59-78.