An adaptive sharp boundary inversion scheme is developed to improve resolution with feasibility for transient electromagnetic (TEM) data inversion. By using weighted minimum gradient support (WMGS) constraint, this method focuses the resistivity change areas on layer boundary locations. Prior information describing roughness can be added into the constraint to improve resolution. Furthermore, even though no prior information about layer boundaries is available, it can still reconstruct models with geo-electrical interfaces. Synthetic models prove that this method has a better performance in presenting layer boundaries than smooth-model inversion. Field data of a TEM test line are inverted using this method, which makes the basement layer visualized easily.
2. Fitterman, D. V. and M. T. Stewart, "Transient electromagnetic sounding for groundwater," Geophysics, Vol. 51, No. 4, 995-1005, 1986.
3. Tantum, S. L. and L. M. Collins, "A comparison of algorithms for subsurface target detection and identification using time-domain electromagnetic induction data," IEEE Transactions on Geoscience and Remote Sensing, Vol. 39, No. 6, 1299-1306, 2001.
4. Nabighian, M. and J. Corbett, "Electromagnetic methods in applied geophysics, Vol. 1: Theory," SEG, 1988.
5. Rodi, W. and R. L. Mackie, "Nonlinear conjugate gradients algorithm for 2-D magnetotelluric inversion," Geophysics, Vol. 66, No. 1, 174-187, 2001.
6. Tikhonov, A. N. and V. I. Arsenin, "Solutions of ill-posed problems," Mathematics of Computation, Vol. 14, Winston, Washington, DC, 1977.
7. Constable, S. C., R. L. Parker, and C. G. Constable, "Occam’s inversion: A practical algorithm for generating smooth models from electromagnetic sounding data," Geophysics, Vol. 52, No. 3, 289-300, 1987.
8. Qian, W., T. J. Gamey, J. S. Holladay, R. Lewis, and D. Abernathy, "Inversion of airborne electromagnetic data using an Occam technique to resolve a variable number of layers," Symposium on the Application of Geophysics to Engineering and Environmental Problems, 735-743, Society of Exploration Geophysicists, January 1997.
9. Vallée, M. A. and R. S. Smith, "Application of Occam’s inversion to airborne time-domain electromagnetics," The Leading Edge, Vol. 28, No. 3, 284-287, 2009.
10. Smith, J. T. and J. R. Booker, "Rapid inversion of two- and three-dimensional magnetotelluric data," Geophys. Res., 3905-3922, 1991.
11. Marquardt, D. W., "An algorithm for least-squares estimation of nonlinear parameters," Journal of the Society for Industrial and Applied Mathematics, Vol. 11, No. 2, 431-441, 1963.
12. Auken, E. and A. V. Christiansen, "Layered and laterally constrained 2D inversion of resistivity data," Geophysics, Vol. 69, No. 3, 752-761, 2004.
13. Portniaguine, O. and M. S. Zhdanov, "Focusing geophysical inversion images," Geophysics, Vol. 64, No. 3, 874-887, 1999.
14. Zhdanov, M. S., R. Ellis, and S. Mukherjee, "Three-dimensional regularized focusing inversion of gravity gradient tensor component data," Geophysics, Vol. 69, No. 4, 925-937, 2004.
15. Loke, M. H., I. Acworth, and T. Dahlin, "A comparison of smooth and blocky inversion methods in 2D electrical imaging surveys," Exploration Geophysics, Vol. 34, No. 3, 182-187, 2003.
16. Wu, X., et al., "Contrast test of the transient electromagnetic system (CASTEM) at the Dawangzhuang iron mine in Anhui province," Chinese J. Geophys., Vol. 59, No. 12, 4448-4456, 2016, doi: 10.6038/cjg20161207.
17. Anderson, W. L., "A hybrid fast Hankel transform algorithm for electromagnetic modeling," Geophysics, Vol. 54, No. 2, 263-266, 1989.
18. Johansen, H. K. and K. Sørensen, "Fast Hankel transforms," Geophysical Prospecting, Vol. 27, No. 4, 876-901, 1979.
19. Cakoni, F. and D. Colton, Qualitative Methods in Inverse Scattering Theory: An Introduction, Springer Science & Business Media, 2005.
20. Hansen, P. C., "Analysis of discrete ill-posed problems by means of the L-curve," SIAM Review, Vol. 34, No. 4, 561-580, 1992.