Browse > Article

Robust 1D inversion of large towed geo-electric array datasets used for hydrogeological studies  

Allen, David (Groundwater Imaging Pty. Ltd.)
Merrick, Noel (National Centre for Groundwater Management, University of Technology Sydney)
Publication Information
Geophysics and Geophysical Exploration / v.10, no.1, 2007 , pp. 50-59 More about this Journal
Abstract
The advent of towed geo-electrical array surveying on water and land has resulted in datasets of magnitude approaching that of airborne electromagnetic surveying and most suited to 1D inversion. Robustness and complete automation is essential if processing and reliable interpretation of such data is to be viable. Sharp boundaries such as river beds and the top of saline aquifers must be resolved so use of smoothness constraints must be minimised. Suitable inversion algorithms must intelligently handle low signal-to-noise ratio data if conductive basement, that attenuates signal, is not to be misrepresented. A noise-level aware inversion algorithm that operates with one elastic thickness layer per electrode configuration has been coded. The noise-level aware inversion identifies if conductive basement has attenuated signal levels so that they are below noise level, and models conductive basement where appropriate. Layers in the initial models are distributed to span the effective depths of each of the geo-electric array quadrupoles. The algorithm works optimally on data collected using geo-electric arrays with an approximately exponential distribution of quadrupole effective depths. Inversion of data from arrays with linear electrodes, used to reduce contact resistance, and capacitive-line antennae is plausible. This paper demonstrates the effectiveness of the algorithm using theoretical examples and an example from a salt interception scheme on the Murray River, Australia.
Keywords
geo-electric; inversion; resistivity; hydrogeology; rivers;
Citations & Related Records
연도 인용수 순위
  • Reference
1 Day-Lewis, F. D., White, E. A., Johnson, C. D., Belaval, M., and Lane, J. W., Jr, 2006, Continuous resistivity profiling to delineate submarine groundwater discharge - examples and limitations: The Leading Edge 25, 724-728. doi:10.1190/1.2210056   DOI   ScienceOn
2 Loke, M. H., and Lane, J.W., 2004, Inversion of data from electrical imaging surveys in water-covered areas: Exploration Geophysics 35, 266-271   DOI
3 MacInnes, S., and Raymond, M., 2001, TS2DIP - Smooth-Model Resistivity and IP Inversion with topography version 4.00, Zonge Engineering and Research Organization, Inc
4 Merrick, N. P., 1997, A new resolution index for resistivity electrode arrays: Exploration Geophysics 28, 106-109   DOI
5 O'Neill,D. J., and Merrick, N. P., 1984,A Digital Linear Filter for Resistivity Sounding with a Generalized Electrode Array: Geophysical Prospecting 32, 105-123. doi:10.1111/j.1365-2478.1984.tb00720.x   DOI   ScienceOn
6 Barrett, B., Hatch, M., Heinson, G., and Telfer, A., 2003, Salinity monitoring of the Murray River using a towed TEM array: 16th Geophysical Conference and Exhibition, Australian Society of Exploration Geophysicists, Extended Abstracts
7 Allen, D. A., and Merrick, N. P., 2006, Aquifer and watercourse interaction in the Murray-Darling Basin elucidated using electrical conductivity imaging: 18th Geophysical Conference and Exhibition, Australian Society of Exploration Geophysicists, Extended Abstracts
8 Allen, D. A., 2006, Electrical Conductivity Imaging of aquifers connected to watercourses, A thesis focussed in the Murray Darling Basin, Australia: PhD Thesis, University of Technology Sydney
9 Roy, A., and Apparao, A., 1971, Depth of investigation in direct current methods: Geophysics 36, 943-959. doi:10.1190/1.1440226   DOI
10 Auken, E., Foged, N., and Sorensen, K. I., 2002, Model recognition by 1-D laterally constrained inversion of resistivity data: 9th Meeting, Environmental and Engineering Geophysical Society-European Section, Proceedings, 241-244
11 Allen, D. A., and Merrick, N. P., 2005, Towed geo-electric arrays for analysis of surface water groundwater interaction: Proceedings of the Symposium on Applications of Geophysics to Engineering and Environmental Problems conference
12 Santos, A. M., 2004, 1-D laterally constrained inversion of EM34 profiling data: Journal of Applied Geophysics 56, 123-134. doi:10.1016/j.jappgeo.2004.04.005   DOI   ScienceOn