1887
  1. Home
  2. A-Z Publications
  3. Near Surface Geophysics
  4. Volume 3, Issue 3
  5. Article
Volume 3 Number 3
  • ISSN: 1569-4445
  • E-ISSN: 1873-0604

Abstract

ABSTRACT

This paper aims to investigate the magnetic resonance signal generated by shallow aquifers and its influence on the interpretation of magnetic resonance sounding (MRS) data. To improve the accuracy of MRS modelling in the presence of shallow aquifers, an enhanced mathematical model, which takes into account the higher harmonics of the transmitted pulse and a non‐zero frequency offset between the Larmor frequency and the pulse frequency, is used. It is shown that in the presence of shallow aquifers, the magnetic resonance signal is complex even when the subsurface has a low electrical conductivity. At large pulse moments, water in shallow aquifers may generate a signal comparable in amplitude to a signal generated by water in deeper aquifers. Two types of error related to a shallow aquifer may occur. For a one‐aquifer system, interpretation using the simplified model may reveal an artefact that appears to be a deeper aquifer, although in reality it is non‐existent (a phantom aquifer). For a multi‐aquifer system, the signal from a shallow aquifer may offset the signal from a deeper aquifer, thus reducing the depth of investigation in comparison with a simple one‐aquifer formation (offset of a deep aquifer).

It is shown numerically that the depth resolution of the MRS method could be significantly improved by considering not only the amplitude but also the phase of the MRS signal. However, taking into account the non‐linearity of the spin system for a large flip angle, the mathematical model for the inversion of complex signals needs to be further improved or at least checked for consistency before inversion.

For verification of the numerical results, a re‐interpretation of MRS field data reported in the literature is presented.

© European Association of Geoscientists and Engineers © 2005 European Association of Geoscientists and Engineers
Loading

Article metrics loading...

/content/journals/10.3997/1873-0604.2005008
2005-02-01
2024-04-23

  • From This Site

    /content/journals/10.3997/1873-0604.2005008
    dcterms_title,dcterms_subject,pub_keyword
    -contentType:Journal -contentType:Contributor -contentType:Concept -contentType:Institution
    10
    5
Loading full text...

Full text loading...

References

  1. BraunM., HertrichM. and YaramanciU.2003. SNMR investigations with variable parameters and loop geometries – a comprehensive study. Proceedings of the 2nd International Workshop on the Magnetic Resonance Sounding Method Applied to Non‐invasive Groundwater Investigations, Orléans, France, pp. 137–140. ISBN 2‐7159‐0936‐5
     [Google Scholar]
  2. LegchenkoA.2004a.Magnetic resonance sounding: enhanced modeling of a phase shift. Applied Magnetic Resonance25, 621–636.
     [Google Scholar]
  3. LegchenkoA.2004b. Applicability of the linear model to interpretation of magnetic resonance soundings. Proceedings of the 10th EEGS‐ES meeting, Utrecht, The Netherlands (CD ROM edition).
     [Google Scholar]
  4. LegchenkoA., BaltassatJ.‐M. and VouillamozJ.‐M.2003. A complex geophysical approach to the problem of groundwater investigation. Proceedings of SAGEEP Annual Meeting, San Antonio, USA, pp. 739–757.
     [Google Scholar]
  5. LegchenkoA.V. and ShushakovO.A.1998. Inversion of surface NMR data. Geophysics63, 75–84.
     [Google Scholar]
  6. LegchenkoA. and VallaP.2002. A review of the basic principles for proton magnetic resonance sounding measurements. Journal of Applied Geophysics50, 3–19.
     [Google Scholar]
  7. LubczynskiM.W. and RoyJ.2003. Hydrogeological interpretation and potential of the new magnetic resonance sounding (MRS) method. Journal of Hydrology283, 19–40.
     [Google Scholar]
  8. LubczynskiM.W. and RoyJ.2004. Magnetic resonance sounding (MRS) – new method for ground water assessment. Journal of Ground Water42(1), 291–303.
     [Google Scholar]
  9. MansfieldP., MaudsleyA.A., MorrisP.G. and PykettI.L.1979. Selective pulses in NMR imaging: reply to criticism. Journal of Magnetic Resonance33, 261–274.
     [Google Scholar]
  10. PlataJ.L. and RubioF.2003. Is MRS methodology ready to fulfil hydrogeologists demands?Proceedings of the 2nd International Workshop on the Magnetic Resonance Sounding Method Applied to Non‐invasive Groundwater Investigations, Orleans, France, pp. 17–20. ISBN 27159‐0936‐5
     [Google Scholar]
  11. RoyJ. and LubczynskiM.2003. The case of an MRS‐elusive second aquifer. Proceedings of the 2nd International Workshop on the Magnetic Resonance Sounding Method Applied to Non‐invasive Groundwater Investigations, Orléans, France, pp. 105–108. ISBN 27159‐0936‐5
     [Google Scholar]
  12. ShushakovO.A.1996. Groundwater NMR in conductive water. Geophysics61, 998–1006.
     [Google Scholar]
  13. TrushkinD.V., ShushakovO.A. and LegchenkoA.V.1994. The potential of a noise‐reducing antenna for surface NMR ground water surveys in the earth’s magnetic field. Geophysical Prospecting42, 855–862.
     [Google Scholar]
  14. TrushkinD.V., ShushakovO.A. and LegchenkoA.V.1995. Surface NMR applied to an electroconductive medium. Geophysical Prospecting43, 623–633.
     [Google Scholar]
  15. WeichmanP.B., LunD.R., RitzwollerM.H. and LavelyE.M.2002. Study of surface nuclear magnetic resonance inverse problems. Journal of Applied Geophysics50, 131–147.
     [Google Scholar]
  16. YaramanciU., LangeG. and HertrichM.2002. Aquifer characterization using surface NMR jointly with other geophysical techniques at the Nauen/Berlin test site. Journal of Applied Geophysics50, 47–65.
     [Google Scholar]
http://instance.metastore.ingenta.com/content/journals/10.3997/1873-0604.2005008
Loading
Improved modelling of the magnetic resonance signal in the presence of shallow aquifers
Near Surface Geophysics 3, 121 (2005); https://doi.org/10.3997/1873-0604.2005008
/content/journals/10.3997/1873-0604.2005008
/content/journals/10.3997/1873-0604.2005008
Loading

Data & Media loading...

  • Article Type: Research Article

Most Cited This Month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error