1887
Volume 45, Issue 4
  • ISSN: 0812-3985
  • E-ISSN: 1834-7533

Abstract

[

Acquisition of magnetic gradient tensor data is likely to become routine in the near future. New methods for inverting gradient tensor surveys to obtain source parameters have been developed for several elementary, but useful, models. These include point dipole (sphere), vertical line of dipoles (narrow vertical pipe), line of dipoles (horizontal cylinder), thin dipping sheet, and contact models. A key simplification is the use of eigenvalues and associated eigenvectors of the tensor. The normalised source strength (NSS), calculated from the eigenvalues, is a particularly useful rotational invariant that peaks directly over 3D compact sources, 2D compact sources, thin sheets and contacts, and is independent of magnetisation direction. In combination the NSS and its vector gradient determine source locations uniquely. NSS analysis can be extended to other useful models, such as vertical pipes, by calculating eigenvalues of the vertical derivative of the gradient tensor. Inversion based on the vector gradient of the NSS over the Tallawang magnetite deposit obtained good agreement between the inferred geometry of the tabular magnetite skarn body and drill hole intersections. Besides the geological applications, the algorithms for the dipole model are readily applicable to the detection, location and characterisation (DLC) of magnetic objects, such as naval mines, unexploded ordnance, shipwrecks, archaeological artefacts, and buried drums.

,

New methods for inverting gradient tensor surveys, based on eigenanalysis and the normalised source strength derived from the eigenvalues, have been developed for point dipole (sphere), vertical line of dipoles (narrow vertical pipe), line of dipoles (horizontal cylinder), thin dipping sheet, and contact models.

]
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2014-12-01
2026-01-18

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References

  1. Anton, H., and Rorres, C., 2000, Elementary linear algebra: applications version, 8th edition: Wiley.
  2. Beiki M Pedersen L. B. 2010 Eigenvector analysis of gravity gradient tensor to locate geologic bodies: Geophysics 75 I37 I49 10.1190/1.3484098
    https://doi.org/10.1190/1.3484098 [Google Scholar]
  3. Beiki M. Pedersen L. B. Nazi H. 2011 Interpretation of aeromagnetic data using eigenvector analysis of pseudogravity gradient tensor: Geophysics 76 L1 L10 10.1190/1.3555343
    https://doi.org/10.1190/1.3555343 [Google Scholar]
  4. Beiki M. Clark D. A. Austin J. R. Foss C. A. 2012 Estimating source location using normalized magnetic source strength calculated from magnetic gradient tensor data: Geophysics in press.
    [Google Scholar]
  5. Blakely, R. J., 1996, Potential theory in gravity and magnetic applications: Cambridge University Press.
  6. Bracken, R. E., and Brown, P. J., 2006, Concepts and procedures required for successful reduction of tensor magnetic gradiometer data obtained from an unexploded ordnance detection demonstration at Yuma Proving Grounds, Arizona, US: Geological Survey Open-File Report (United States), 2006–1027, 53 pp.
  7. Christensen A. Rajagopalan S. 2000 The magnetic vector and gradient tensor in mineral and oil exploration: Preview 84 77
    [Google Scholar]
  8. Chwala, A., Stolz, R., Zakosarenko, V., Fritzsch, L., Shulz, M., Rompel, A., Polome, L., Meyer, M., and Meyer, H. G., 2012, Full tensor SQUID gradiometer for airborne exploration. Australian Society of Exploration Geophysicists, 22nd International Geophysical Conference and Exhibition, 26–29 February 2012 - Brisbane, Australia, CD-ROM, 4 pp.
  9. Clark, D. A., 2010, Method and apparatus for detection using magnetic gradient tensor. US Patent Application Pub. No.: US 2010/0211337 Al, Pub. date: Aug. 19, 2010.
  10. Clark, D. A., 2012a, New methods for interpretation of magnetic gradient tensor data. Australian Society of Exploration Geophysicists, 22nd International Geophysical Conference and Exhibition, 26–29 February 2012 - Brisbane, Australia, CD-ROM, 11 pp.
  11. Clark, D. A., 2012b, Interpretation of the magnetic gradient tensor and normalized source strength applied to the Tallawang magnetite skarn deposit, New South Wales, Australia. Society of Exploration Geophysicists Annual Meeting, Las Vegas.
  12. Clark D. A. Schmidt P. W. Coward D. A. Huddleston M. P. 1998 Remote determination of magnetic properties and improved drill targeting of magnetic anomaly sources by Differential Vector Magnetometry (DVM): Exploration Geophysics 29 312 319 10.1071/EG998312
    https://doi.org/10.1071/EG998312 [Google Scholar]
  13. Clark, D. A., Young, J. A., and Schmidt, P. W., 2009, Magnetic tensor gradiometry in the marine environment: correction of electric and magnetic field and gradient measurements in a conductive medium and improved methods for magnetic target location using the magnetic gradient tensor. MARELEC (Marine Electromagnetics) Conference, July 2009, Stockholm, CD-ROM, 10 pp.
  14. Clem T. R. Froelich M. C. Overway D. J. Purpura J. W. Wiegert R. F. Koch R. H. Lathrop D. K. Rozen J. Eraker J. H. Schmidt J. M. 1997 Advances in sensor development and demonstration of superconducting gradiometers for mobile operation: IEEE Transactions on Applied Superconductivity 7 3287 3293 10.1109/77.622056
    https://doi.org/10.1109/77.622056 [Google Scholar]
  15. Clem T. R. Overway D. J. Purpura J. W. Bono J. T. Koch R. H. Rozen J. Keeefe G. A. Willen S. Mohling R. A. 2001 High-Tc SQUID gradiometer for mobile magnetic anomaly detection: IEEE Transactions on Applied Superconductivity 11 871 875 10.1109/77.919483
    https://doi.org/10.1109/77.919483 [Google Scholar]
  16. Emerson D. W. Clark D. A. Saul S. J. 1985 Magnetic exploration models incorporating remanence, demagnetization and anisotropy: HP 41C handheld computer algorithms: Exploration Geophysics 16 1 122 10.1071/EG985001
    https://doi.org/10.1071/EG985001 [Google Scholar]
  17. Fitzgerald D. Holstein H. 2006 Innovative data processing methods for gradient airborne geophysical data sets: The Leading Edge 25 87 94 10.1190/1.2164762
    https://doi.org/10.1190/1.2164762 [Google Scholar]
  18. Fitzgerald, D., Argast, D., Paterson, R., and Holstein, H., 2009, Full tensor magnetic gradiometery processing and interpretation developments. 11th SAGA Technical Meeting and Exhibition, 16–18 September 2009, Swaziland, 265–272.
  19. Fitzgerald D. Argast D. Paterson R. Holstein H. 2010 Progress on interpreting dykes from full tensor magnetic gradiometry: SEG Expanded Abstracts 29 1162 1166 10.1190/1.3513050
    https://doi.org/10.1190/1.3513050 [Google Scholar]
  20. Foss C. 2006 The improvements in source resolution that can be expected from inversion of magnetic field tensor data: The Leading Edge 25 81 84 10.1190/1.2164761
    https://doi.org/10.1190/1.2164761 [Google Scholar]
  21. Heath, P., 2007, Analysis of potential field gradient data: forward modelling, inversion and near-surface exploration: Ph.D. thesis, University of Adelaide.
  22. Holstein, H., Fitzgerald, D., Willis, C. P., and Foss, C., 2011, Magnetic gradient tensor eigenanalysis for dyke location. 73rd EAEG Conference and Exhibition, 23–27 May 2011, Vienna.
  23. Humphrey K. P. Horton T. J. Keene M. N. 2005 Detection of mobile targets from a moving platform using an actively shielded, adaptively balanced SQUID gradiometer: IEEE Transactions on Applied Superconductivity 15 753 756 10.1109/TASC.2005.850038
    https://doi.org/10.1109/TASC.2005.850038 [Google Scholar]
  24. Ku C. C. Sharp J. A. 1983 Werner deconvolution for automated magnetic interpretation and its refinement using Marquardt’s inverse modelling: Geophysics 48 754 774
    [Google Scholar]
  25. Leslie, K. E., Bick, M., Binks, R. A., Tilbrook, D. L., Clark, D. A., Schmidt, P. W., Cusack, P. J., Thorn, R. G., Blay, K. R., and Sullivan, P. R., 2005, Performance issues for a spinning gradiometer. 10th International Superconductive Electronics Conference (ISEC 2005), Noordwijkerhout, The Netherlands, 2005. ISEC Extended Abstracts (Univ. Twente) O-O.01.
  26. Leslie, K. E., Blay, K., Clark, D., Schmidt, P., Tilbrook, D., Bick, M., and Foley, C., 2007, Helicopter trial of magnetic tensor gradiometer. ASEG 19th International Conference, December 2007, Perth, Western Australia, CD-ROM, 4 pp.
  27. Li X. 2006 Understanding the 3D analytic signal amplitude: Geophysics 71 L13 L16
    [Google Scholar]
  28. Lima, E. A., Irimia, A., and Wikswo, J. P., 2006, The magnetic inverse problem, in J. Clarke and A.I. Braginski, eds., The SQUID Handbook, Vol. II Applications of SQUIDs and SQUID Systems: Wiley-VCH, pp. 139–267.
  29. McRae, W., Veryaskin, A. V., Greager, D., Ju, L., Blair, D., Chin, E.-J., Dumas, J.-C., and Lee, B., 2004, String magnetic gradiometer system: recent airborne trials: 74th Ann. Mtg. Soc. Explor. Geophys., Expanded Abstracts 23, 790–793.
  30. 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 37 501 517
    [Google Scholar]
  31. Nara T. Suzuki S. Ando S. 2006 A closed-form formula for magnetic dipole localization by measurement of its magnetic field and spatial gradients: IEEE Transactions on Magnetics 42 3291 3293 10.1109/TMAG.2006.879151
    https://doi.org/10.1109/TMAG.2006.879151 [Google Scholar]
  32. Pedersen L. B. Rasmussen T. M. 1990 The gradient tensor of potential field anomalies: some implications on data collection and data processing of maps: Geophysics 55 1558 1566
    [Google Scholar]
  33. Schmidt, P. W., 2006, Inversion using Euler deconvolution of the magnetic gradient tensor. Australian Earth Sciences Congress, Melbourne, Australia, Extended Abstracts, 3 pp.
  34. Schmidt P. W. Clark D. A. 2006 The magnetic gradient tensor: its properties and uses in source characterization: The Leading Edge 25 75 78 10.1190/1.2164759
    https://doi.org/10.1190/1.2164759 [Google Scholar]
  35. Schmidt P. Clark D. Leslie K. Bick M. Tilbrook D. Foley C. 2004 GETMAG – A SQUID magnetic tensor gradiometer for mineral and oil exploration: Exploration Geophysics 35 297 305 10.1071/EG04297
    https://doi.org/10.1071/EG04297 [Google Scholar]
  36. Stolz R. Fritzsch L. Meyer H.-G. 1999 LTS SQUID sensor with a new configuration: Superconductor Science and Technology 12 806 808 10.1088/0953‑2048/12/11/334
    https://doi.org/10.1088/0953-2048/12/11/334 [Google Scholar]
  37. Stolz R. Zakosarenko V. Schulz M. Chwala A. Fritzsch L. Meyer H.-G. Köstlin E. O. 2006 a Magnetic full-tensor SQUID gradiometer system for geophysical applications: The Leading Edge 25 178 180 10.1190/1.2172308
    https://doi.org/10.1190/1.2172308 [Google Scholar]
  38. Stolz R. Chwala A. Zakosarenko V. Schulz M. Fritzsch L. Meyer H.-G. 2006 b SQUID technology for geophysical exploration: SEG Expanded Abstracts 25 894 898 10.1190/1.2370400
    https://doi.org/10.1190/1.2370400 [Google Scholar]
  39. Sunderland A. Golden H. McRae W. Veryaskin A. Ju L. Blair D. 2009 Results from a novel direct magnetic gradiometer: Exploration Geophysics 40 222 226 10.1071/EG08121
    https://doi.org/10.1071/EG08121 [Google Scholar]
  40. Tilbrook D. L. 2004 The design of a new concept HTSC axial gradiometer: Physica C: Superconductivity 407 1 9 10.1016/j.physc.2004.04.025
    https://doi.org/10.1016/j.physc.2004.04.025 [Google Scholar]
  41. Tilbrook, D. L., Clark, D. A., and Blay, K. R., 2006, Data extraction and calibration of a superconducting rotating magnetic tensor gradiometer. Applied Superconductivity Conference, 27 August – 1 September 2006, Seattle, USA.
  42. Veryaskin A. V. 2001 Magnetic gradiometry: a new method for magnetic gradient measurement: Sensors and Actuators A: Physical 91 233 235 10.1016/S0924‑4247(01)00489‑7
    https://doi.org/10.1016/S0924-4247(01)00489-7 [Google Scholar]
  43. Wiegert R. Oeschger J. Tuovila E. 2007 Demonstration of a novel man-portable magnetic STAR technology for real time localization of unexploded ordnance : Proceedings of MTS/IEEE Oceans 2007 1 7 10.1109/OCEANS.2007.4449229
    https://doi.org/10.1109/OCEANS.2007.4449229 [Google Scholar]
  44. Wilson, H., 1985, Analysis of the magnetic gradient tensor. Defence Research Establishment Pacific, Canada, Technical Memorandum, 85–13, 47.
  45. Wynn W. M. 1995 Magnetic dipole localization using the gradient rate tensor measured by a five-axis magnetic gradiometer with known velocity: Proceedings of the Society for Photo-Instrumentation Engineers 2496 357 367 10.1117/12.211331
    https://doi.org/10.1117/12.211331 [Google Scholar]
  46. Wynn W. M. 1997 Magnetic dipole localization with a gradiometer: obtaining unique solutions. IGARSS ’97, Remote Sensing – A Scientific Vision for Sustainable Development, Geoscience and Remote Sensing, 3–8 August 1997: IEEE International 4 1483 1485 10.1109/IGARSS.1997.608906
    https://doi.org/10.1109/IGARSS.1997.608906 [Google Scholar]
  47. Wynn, W. M., 1999, Detection, localization, and characterization of static magnetic-dipole sources, in C. E. Baum, ed., Detection and identification of visually obscured targets: Taylor & Francis, pp. 337–374.
  48. Wynn W. M. Frahm C. P. Carroll P. J. Clark R. H. Wellhoner J. Wynn M. J. 1975 Advanced super-conducting gradiometer/magnetometer arrays and a novel signal processing technique: IEEE Transactions on Magnetics 11 701 707 10.1109/TMAG.1975.1058672
    https://doi.org/10.1109/TMAG.1975.1058672 [Google Scholar]
  49. Young, J. A., Keenan, S. T., Clark, D. A., Leslie, K. E., Sullivan, P., Fairman, P., Williams, C., Foley, C. P., and Billings, S. D., 2010, A superconducting magnetic tensor gradiometer for underwater UXO detection. 21st International Geophysical Conference & Exhibition (ASEG-PESA 2010), Sydney (extended abstract), CD-ROM, 4 pp.
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Corrigendum to: New methods for interpretation of magnetic vector and gradient tensor data I: eigenvector analysis and the normalised source strength
Exploration Geophysics 45, 267 (2014); https://doi.org/10.1071/EG12020_CO
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  • Article Type: Research Article
Keyword(s): dipole localisation, eigenvalues, eigenvectors, magnetic field vector, magnetic gradient tensor, magnetisation, normalised source strength.

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