Combined weighted inversion of electrical resistivity data arising from different array types

Athanasiou, Evangelia; Τσούρλος, Π.; Papazachos, C. B.; Τσοκασ, Γ. Ν.

doi:10.1016/j.jappgeo.2006.09.003

Cited by 62 publications

(42 citation statements)

References 17 publications

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“…As a result, a combination of the two techniques is usually applied. ERT (Tsourlos and Ogilvy 1999;Stummer et al 2004;Wilkinson et al 2006;Tsourlos et al 2006;Kemna et al 2006;Athanasiou et al 2007;Papadopoulos et al 2006Papadopoulos et al , 2007 is a usual and reliable approach to this problem. ERT profiles can be measured either in two dimensions, with the assumption that minor variation exists in bulk material values in the third (normally the y) dimension, or in three dimensions.…”

Section: Discussionmentioning

confidence: 99%

Coastal aquifer assessment based on geological and geophysical survey, northwestern Crete, Greece

et al. 2009

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Groundwater preservation comprises a major problem in water policy. The comprehension of the groundwater/hydraulic systems can provide the means to approach this problem. Generally, drilling is expensive and time-consuming. On the other hand, new techniques have been applied during the last few decades that provide useful information on the depth and quality of aquifers. Among them, transient electromagnetic method (TEM) is an appealing method that provides fast results with minimum field crew and solves several hydrogeological problems. Many portable systems for single-site measurements are commercially available. The TEM-Fast 48HPC was used for acquiring 106 soundings in the northwestern Crete in Greece for defining the hydrogeological characteristics of the study area, since there were no available data from boreholes. Detailed geological, hydrolithological and tectonic survey was applied prior to the geophysical measurements. All the data were integrated to produce a secure and reliable hydrogeological model for the study area prior to any future hydrowell. Specifically, geometrical and hydraulic data of the study area groundwater were acquired. Two unconnected aquifers were detected and their possible contamination due to saltwater intrusion was analyzed and eliminated. Moreover, a location for borehole construction and groundwater pumping based on the potential of the aquifer system was proposed. Finally, the contribution of TEM (and electrical resistivity tomography) geophysical methods in studying complex coastal aquifers is shown by this work.

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Section: Discussionmentioning

confidence: 99%

Coastal aquifer assessment based on geological and geophysical survey, northwestern Crete, Greece

et al. 2009

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“…Several authors consider methods for efficiently combining ERI arrays to improve subsurface resolution (e.g., Athanasiou et al 2007;Ishola et al 2015;Loke et al 2007). For any given set of electrodes, the total possible number of non-reciprocal electrode combinations is given below (Noel and Xu 1991;Stummer et al 2002) where n represents the number of electrodes present in the array.…”

Section: Background: Electrical Resistivity Imagingmentioning

confidence: 99%

Electrical Resistivity Imaging and the Saline Water Interface in High-Quality Coastal Aquifers

2018

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Population growth and changing climate continue to impact on the availability of natural resources. Urbanization of vulnerable coastal margins can place serious demands on shallow groundwater. Here, groundwater management requires definition of coastal hydrogeology, particularly the seawater interface. Electrical resistivity imaging (ERI) appears to be ideally suited for this purpose. We investigate challenges and drivers for successful electrical resistivity imaging with field and synthetic experiments. Two decades of seawater intrusion monitoring provide a basis for creating a geo-electrical model suitable for demonstrating the significance of acquisition and inversion parameters on resistivity imaging outcomes. A key observation is that resistivity imaging with combinations of electrode arrays that include dipole-dipole quadrupoles can be configured to illuminate consequential elements of coastal hydrogeology. We extend our analysis of ERI to include a diverse set of hydrogeological settings along more than 100 km of the coastal margin passing the city of Perth, Western Australia. Of particular importance are settings with: (1) a classic seawater wedge in an unconfined aquifer, (2) a shallow unconfined aquifer over an impermeable substrate, and (3) a shallow multi-tiered aquifer system over a conductive impermeable substrate. We also demonstrate a systematic increase in the landward extent of the seawater wedge at sites located progressively closer to the highly urbanized center of Perth. Based on field and synthetic ERI experiments from a broad range of hydrogeological settings, we tabulate current challenges and future directions for this technology. Our research contributes to resolving the globally significant challenge of managing seawater intrusion at vulnerable coastal margins.

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“…Moreover, DE LA VEGA et al (2003) used a combined inversion algorithm for different electrode array data sets with the combined inversion images outperforming the inversion results obtained from separate electrode arrays. ATHANASIOU et al (2007) introduced a weighting factor to the two-dimensional (2D) combined inversion algorithm, which prevented the dominance of one array type over another as the applied parameter allowed equal participation of the data from an individual array.…”

Section: Introductionmentioning

confidence: 99%

Combining Multiple Electrode Arrays for Two-Dimensional Electrical Resistivity Imaging Using the Unsupervised Classification Technique

Ishola

Nawawi

Abdullah

2014

Pure Appl. Geophys.

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This article describes the use of k-means clustering, an unsupervised image classification technique, to help interpret subsurface targets. The k-means algorithm is employed to combine and classify the two-dimensional (2D) inverse resistivity models obtained from three different electrode arrays. The algorithm is initialized through the selection of the number of clusters, number of iterations and other parameters such as stopping criteria. Automatically, it seeks to find groups of closely related resistivity values that belong to the same cluster and are more similar to each other than resistivity values belonging to other clusters. The approach is applied to both synthetic and field data. The 2D postinversions of the resistivity data were preprocessed by resampling and interpolating to the same coordinate. Following the preprocessing, the three images are combined into a single classified image. All the image preprocessing, manipulation and analysis are performed using the PCI Geomatics software package. The results of the clustering and classification are presented as classified images. An assessment of the performance of the individual and combined images for the synthetic models is carried out using an error matrix, mean absolute error and mean absolute percent error. The estimated errors show that images obtained from maximum values of the reconstructed resistivity for the different models give the best representation of the true models. Additionally, the overall accuracy and kappa values show good agreement between the combined classified images and true models. Depending on the model, the overall accuracy ranges from 86 to 99 %, while the kappa coefficient is in the range of 54-98 %. Classified images with kappa coefficients greater than 0.8 show strong agreement, while images with kappa coefficients greater than 0.5 but less than 0.8 give moderate agreement. For the field data, the k-mean classifier produces images that incorporate structural features of the three electrode array configurations. Consequently, some clusters that overwhelmingly correspond to the lithologic units of the investigated areas are better identified than the tomographic images of each data set considered separately, underscoring the relevance of the unsupervised classification technique in this study.

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Combined weighted inversion of electrical resistivity data arising from different array types

Cited by 62 publications

References 17 publications

Coastal aquifer assessment based on geological and geophysical survey, northwestern Crete, Greece

Coastal aquifer assessment based on geological and geophysical survey, northwestern Crete, Greece

Electrical Resistivity Imaging and the Saline Water Interface in High-Quality Coastal Aquifers

Combining Multiple Electrode Arrays for Two-Dimensional Electrical Resistivity Imaging Using the Unsupervised Classification Technique

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