Abstract：
Magnetic anomalies are often disturbed by the magnetization direction, so we can’t directly use the original magnetic anomaly to estimate the exact location and geometry of the source. The 2D analytic signal is insensitive to magnetization direction. In this paper, we present an automatic method based on the analytic signal horizontal and vertical derivatives to interpret the magnetic anomaly. We derive a linear equation using the analytic signal properties and we obtain the 2D magnetic body location parameters without giving a priori information. Then we compute the source structural index (expressing the geometry) by the estimated location parameters. The proposed method is demonstrated on synthetic magnetic anomalies with noise. For different models, the proposed technique can both successfully estimate the location parameters and the structural index of the sources and is insensitive to noise. Lastly, we apply it to real magnetic anomalies from China and obtain the distribution of unexploited iron ore. The inversion results are consistent with the parameters of known ore bodies.
MA Guo-Qing,DU Xiao-Juan,LI Li-Li et al. Interpretation of magnetic anomalies by horizontal and vertical derivatives of the analytic signal[J]. APPLIED GEOPHYSICS, 2012, 9(4): 468-474.
[1]
Bastani, M., and Pedersen, L. B., 2001, Automatic interpretation of magnetic dike parameters using the analytic signal technique: Geophysics, 66, 551 - 561.
[2]
Doo, W. D., Hsu, S. K., and Yeh, Y. C., 2007, A derivative-based interpretation approach to estimating source parameters of simple 2D magnetic sources from Euler deconvolution, the analytic-signal method and analytical expressions of the anomalies: Geophysical Prospecting, 55, 255 - 264.
[3]
Hsu, S. K., Coppens, D., and Shyu, C. T., 1998, Depth to magnetic source using the generalized analytic signal: Geophysics, 63, 1947 - 1957.
[4]
Huang, D., Gubbins, D., Clark, R. A., and Whaler, K. A., 1995, Combined study of Euler’s homogeneity equation for gravity and magnetic field.57th EAGE conference, Glasgow, UK, Extended Abstracts, 144.
[5]
Li, X., 2006, Understanding 3D analytic signal amplitude: Geophysics, 71, L13 - L16.
[6]
Li, X., 2008, Magnetic reduction-to-the-pole at low latitudes: observation and considerations: The leading edge, 990 - 1002.
[7]
Nabighian, M. N., 1972, The analytic signal of two-dimensional magnetic bodies with polygonal cross-section: its properties and use for automated anomaly interpretation: Geophysics, 37, 507 - 517.
[8]
Rao, D., Babu, H., and Narayan, P., 1981, Interpretation of magnetic anomalies due to dikes: The complex gradient method: Geophysics, 46, 1572 - 1578.
[9]
Reid, A. B., Allsop, J. M., Granser, H., Millet, A. J., and Somerton, I. W., 1990, Magnetic interpretation in three dimensions using Euler deconvolution: Geophysics, 55, 80 - 91.
[10]
Roest, W. R., Verhoef, J., and Pilkington, M., 1992, Magnetic interpretation using 3-D analytic signal. Geophysics, 57, 116 - 125.
[11]
Salem, A., Ravat, D., Gamey, T. J., and Ushijima, K., 2002, Analytic signal approach and its applicability in environmental magnetic investigations: Journal of Applied Geophysics, 49, 231 - 244.
[12]
Salem, A., and Ravat, D., 2003, A combined analytic signal and Euler method (AN-EUL) for automatic interpretation of magnetic data: Geophysics, 68(6), 1952 - 1961.
[13]
Salem, A., Ravat, D., Mushayandebvu, M. F., and Ushijima, K., 2004, Linearized least-squares method for interpretation of potential-field data from sources of simple geometry: Geophysics, 69, 783 - 788.
[14]
Salem, A., 2005, Interpretation of magnetic data using analytic signal derivatives: Geophysical Prospecting, 53, 75 - 82.
[15]
Thompson, D. T., 1982, EULDPH’-a new technique for making computer-assisted depth estimates from magnetic data: Geophysics, 47, 31 - 37.
2012, Vol. 9 
