Abstract
<p> <p id="x-x-sp0080"> Electrical resistivity <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/tomography" title="Learn more about Tomography from ScienceDirect's AI-generated Topic Pages"> tomography </a> (ERT) surveys are widely used in geological, environmental and engineering studies. However, the effectiveness of surface <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/landsat-satellite" title="Learn more about Landsat Satellite from ScienceDirect's AI-generated Topic Pages"> ERT </a> surveys is limited by decreasing resolution with depth and near the ends of the survey line. Increasing the array length will increase depth of investigation, but may not be possible at urban sites where access is limited. One novel method of addressing these limitations while maintaining lateral coverage is to install an array of deep electrodes. Referred to here as the Multi-Electrode Resistivity Implant Technique (MERIT), self-driving pointed electrodes are implanted at depth below each surface electrode in an array, using direct-push technology. Optimal sequences of readings have been identified with the “Compare R” method of Wilkinson. Numerical, laboratory, and field case studies are applied to examine the effectiveness of the MERIT method, particularly for use in covered <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/karst" title="Learn more about Karst from ScienceDirect's AI-generated Topic Pages"> karst </a> terrain. In the field case studies, resistivity images are compared against subsurface structure defined from borings, GPR surveys, and knowledge of prior land use. In karst terrain where limestone has a clay overburden, traditional surface resistivity methods suffer from lack of current penetration through the shallow clay layer. In these settings, the MERIT method is found to improve resolution of features between the surface and buried array, as well as increasing depth of penetration and enhancing imaging capabilities at the array ends. The method functions similar to a cross-borehole array between horizontal <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/boreholes" title="Learn more about Boreholes from ScienceDirect's AI-generated Topic Pages"> boreholes </a> , and suffers from limitations common to borehole arrays. Inversion artifacts are common at depths close to the buried array, and because some readings involve high geometric factors, inversions are more susceptible to noise than traditional surface arrays. Results are improved by using errors from reciprocal measurements to weight the data during the inversion. </p></p>
Original language | American English |
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Journal | Journal of Applied Geophysics |
Volume | 135 |
DOIs | |
State | Published - Dec 1 2016 |
Keywords
- Resistivity inversion
- Tomography
- Optimized arrays
- Sinkhole karst features
- MERIT
Disciplines
- Earth Sciences