• Geophysics and Geophysical Exploration
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• v.5 no.4
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• pp.250-256
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• 2002

Resistivity tomography has become an important tool to image underground resistivity distribution. This method has been widely applied to site investigation for engineering and environmental purpose. In resistivity tomography, various electrode arrays can be used and each array has both merits and demerits. For example, the pole-pole array has high signal to noise ratio (S/N ratio), but its resolution is too low. The dipole-dipole array has low S/N ratio, but its resolution is very high. The Pole-dipole may has intermediate Snf ratio and resolution. The modified Pole-dipole array, recently proposed, shows reasonable S/N ratio and resolution, which are comparable to the pole-dipole array. These electrode arrays except the pole-pole array, however, have the problem that the apparent resistivity can diverge at some special electrode Positions. Also, the Pole-Pole array may not reflect the doe resistivity of an anomalous body. In this study, we propose a new electrode array, mixed array, where pole-dipole and modified pole-dipole ways are selectively used with the relative positions of current and potential electrodes. The mixed array has the same level of S/N ratio and resolution as the pole-dipole array and the apparent resistivity does not diverge in the receiver hole. Furthermore, the apparent resistivity using the array can reflect the true resistivity of the anomalous body.

• Journal of the Korean earth science society
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• v.30 no.6
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• pp.699-708
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• 2009

Recently as the interest in the development of domestic ore deposits has increased, we can easily find some studies on exploration geophysics-based ore-deposit survey in literature. Based on the fact that mineralized zone are generally more conductive than surrounding media, electrical resistivity survey among several geophysical surveys has been applied to investigate metallic ore deposits. Most of them are grounded on 2-D survey. However, 2-D inversion may lead to some misinterpretation for 3-D geological structures. In this study, we investigate the feasibility of the 3-D electrical resistivity survey to 3-D vein-type ore deposits. We first simulate 2-D dipole-dipole survey data for survey lines normal to the strike and 3-D pole-pole survey data, and then perform 3-D inversion. For 3-D ore-body structures, we assume a width-varying dyke, a wedge-shaped, and a fault model. The 3-D inversion results are compared to 2-D inversion results. By comparing 3-D inversion results for 2-D dipole-dipole survey data to 3-D inversion results for 3-D pole-pole survey data, we could note that the 2-D dipole-dipole survey data yield better inversion results than the 3-D pole-pole data, which is due to the main characteristic of the pole-pole array. From these results, we are convinced that if we have certain information on the direction of the strike, it would be desirable to apply 2-D dipole-diple survey for the survey lines normal to the strike. However, in most cases, we do not have any information on the direction of the strike, because we already developed the ore deposit with the outcrops and the remaining ore deposits are buried under the surface. In that case, performing 3-D pole-pole electrical resistivity survey would be a reasonable choice to obtain more accurate interpretation on ore body structure in spite of low resolution of pole-pole array.

• Geophysics and Geophysical Exploration
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• v.4 no.3
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• pp.59-69
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• 2001

Five kinds of modified electrode arrays were proposed to overcome the weak points of the commonly used arrays using dipole and/or pole in two-dimensional resistivity surveys. The modified pole-pole array was suggested to overcome the inefficiency caused by distant earthing in pole-pole array. Four kinds of modified arrays using dipole were designed to enhance the signal-to-noise ratio of the conventional dipole-dipole and pole-dipole arrays through boosting up the measured potential difference. In the numerical experiments using the two-dimensional modeling and inversion, the effects of the ambient electrical noise and the resolving power were examined and the results showed the validity of the modified arrays proposed in this study.

• Proceedings of the KSEEG Conference
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• 2002.04a
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• pp.113-114
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• 2002

• Geophysics and Geophysical Exploration
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• v.13 no.4
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• pp.364-369
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• 2010

Resistivity data should be edited before the inversion because resistivity data are contaminated by a lot of noise. Generally, outlier or data violating pants-leg effect in dipole-dipole array were used to be rejected in the apparent resistivity pseudo-section. For more precise data editing, normalized voltage curves are used. In this study, we analyzed the behavior of normalized voltage curves for pole-pole, pole-dipole and dipole-dipole arrays in the presence of threedimensional inhomogeneities, and finally re-examined the validity of normalized voltage curves in the editing process of resistivity data.

• 한국지구물리탐사학회:학술대회논문집
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• 2000.09a
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• pp.19-40
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• 2000

We applied both SP monitoring and pole-pole array resistivity surveys and SP survey and dipole-dipole array resistivity survey to leakage problems in several embankments and dike, respectively, to estimate and detect the zone of leakage. The embankment is generally affected by tidal variation and has low resistivity characteristics due to the high saturation of seawater. According to this situation, SP monitoring and resistivity survey using pole-pole electrode array, which is relatively more effective to the conductive media, were carried out to delineate the leakage zones of sea water through the embankment. We checked out electrical conductivity(EC) and temperature variations along the inner part of the embankment to detect the zone of seawater leakage and found that the measured EC value agreed to that of seawater in the leakage zone and the temperature was lower than that of the vicinity of leakage zone. SP monitoring results were coincide with tidal variations at each embankment. Based on the survey results, it is concluded that both SP monitoring and the pole-pole array resistivity method are quite effective for investigation of seawater leakage zones in the embankment.

• 한국지구물리탐사학회:학술대회논문집
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• 2000.09a
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• pp.112-131
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• 2000

In spite of its many strong points, pole-pole electrode configuration is not often used for ground electrical resistivity survey except for bore hole survey as normal logging and for archaeological investigation. Above all, poor spatial resolution of pole-pole survey may be responsible for this. But recent experiences so far gained by the present authers lead them to think that pole-pole survey can be at least a viable means of reconnaissance survey in near-surface conductive environment and an effective interpretational scheme may augment its resolution. As well known, a response of any other electrode configuration is a linear combination of pole-pole responses. Based on this principle of linear superposition and the principle of reciprocity, the other 'responses' can be derived with simple additions and subtractions of pole-pole responses. Though such responses are not always correct due to the adverse effects of noises, combined with the potential decay curves, they can be helpful to interprete better pole-pole survey data especially in connection of the resolution. This can be comparable to the use of the first or second derivatives of gravity and magnetic intensity surveys.

• The Journal of Engineering Geology
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• v.16 no.3 s.49
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• pp.255-263
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• 2006

In an electrical tomographic survey using an inclined borehole with a pole-dipole array, we must consider several factors: a singular point associated with zero potential difference, a spatial discrepancy between electrode and nodal point in a model due to a inclined borehole, and a variation of geometric factors in connection with a irregular topography. Singular points which are represented by the normal distance from current source to the ground surface can be represented by serveral regions due to a irregular topography of ground surface. The method of element division can be applied to the region in which the borehole is curved, inclined or the distance between the electrodes is shorter than that of nodal points, because the coordinate of each electrode cannot be assigned directly to the nodal point if several electrodes are in an element. Test on a three-dimensional (3-D) synthetic model produces good images of conductive target and shoves stable convergence.

• Geophysics and Geophysical Exploration
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• v.9 no.1
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• pp.44-49
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• 2006

In this study, the resolution capabilities of electrical resistivity tomography (ERT) in the monitoring of $CO_2$ injection are investigated. The pole-pole and bipole-bipole electrode configuration types are used between two uncased boreholes straddling the $CO_2$ plume. Forward responses for an initial pre-injection model and three models for subsequent stages of $CO_2$ injection are calculated for the two different electrode configuration types, noise is added and the theoretical data are inverted with both L1- and L2-norm optimisation. The results show that $CO_2$ volumes over a certain threshold can be detected with confidence. The L1-norm proved superior to the L2-norm in most instances. Normalisation of the inverted models with the pre-injection inverse model gives good images of the regions of changing resistivity, and an integrated measure of the total change in resistivity proves to be a valid measure of the total injected volume.

• The Journal of Engineering Geology
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• v.17 no.2 s.52
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• pp.271-277
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• 2007

To find out the anomalous zone in cut slope composed of phyllite and shist, we performed resistivity tomography using a pole-dipole way. The electrical distribution that propagates from a current source in lower part of slope is measured by a potential electrode in upper part of slope. Apparent resistivity data are inverted with an iterative regularized inversion method to reconstruct 3D resistivity image. By comparing with the resistivity images in relation to each section, the images of anomalous zone correspond to their positions represented in cut slope. Therefore, the application of resistivity tomography in cut slope is useful to recognize the extension of anomalous zone.