• Proceedings of the KSEEG Conference
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• 2000.04b
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• pp.168-170
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• 2000

• Proceedings of the KSEEG Conference
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• 2001.04a
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• pp.83-87
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• 2001

• Proceedings of the KSEEG Conference
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• 2001.04a
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• pp.69-73
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• 2001

• Proceedings of the KSEEG Conference
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• 2001.04a
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• pp.74-77
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• 2001

• Proceedings of the KSEEG Conference
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• 1999.04a
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• pp.321-325
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• 1999

• Geophysics and Geophysical Exploration
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• v.5 no.3
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• pp.199-205
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• 2002

In the resistivity method, the potential difference between two grounded electrodes is measured and this can be positive or negative. The apparent resistivity and the potential difference have the same polarity. Since the electric field is the gradient of the potential, the polarity of the potential difference depends on the direction of the electric field. If the direction of the vector connecting two grounded electrodes is the same to that of the electric field, the measured potential difference and the apparent resistivity become positive. If the opposite is the case, they become negative. In general, the primary electric field and the vector connecting two potential electrodes have the same direction in a surface resistivity method. In this case, the measured potential difference is always positive because the primary electric field is greater than the secondary field. Therefore, the apparent resistivity is always positive if noise is free and topography is flat. The secondary field component, however, can be greater than the primary field component along the vector connecting two potential electrodes in the cross-hole resistivity method. Furthermore, if the secondary electric field and the vector connecting two potential electrodes have an opposite direction, the apparent resistivity become negative. Consequently, the apparent resistivity may be negative in the region where the primary electric field component along the vector connecting two potential electrodes is very small.

• Journal of the Korean Geophysical Society
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• v.7 no.3
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• pp.171-183
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• 2004

Electrical resistivity survey is widely used to investigate the stability of center-core type fill dam against the seepage phenomenon. In this study, we analyze the resistivity information obtained on a earth fill dam and compare it with the geotechnical SPT result. The analysis shows that the zones showing low resistivity value generally have low N value. However, some zones with high resistivity pattern do not accompany the increase of N value, and even showing low N value. These results imply that the direct identification of resistivity value to the real status of the core material of fill dam is impossible, and a highly resistive zone may be in serious status due to the effect increasing the resistivity value by the piping condition. Therefore, multiple exploration should be planned to reduce the uncertainty in application of geophysical methods to dam safety evaluation.

• Geophysics and Geophysical Exploration
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• v.24 no.3
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• pp.98-112
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• 2021

We followed and extended the algorithm originally made by Das (1995) to calculate the electric potential and field induced by electric current in arbitrary anisotropic layered structure. We confirmed all the theoretical contents and coded the corresponding program to acquire the electric potential and field. Further we extended to forward estimation of apparent resistivity to be attained by electrical resistivity survey on anisotropic layered structure with differing the electrode spacing and azimuth of anisotropy. The effects of anisotropy were reviewed by considering some examples.

• Proceedings of the KSEEG Conference
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• 2002.04a
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• pp.110-112
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• 2002

• Journal of the Korean Geophysical Society
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• v.1 no.1
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• pp.51-58
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• 1998

A numerical program has been developed to model 2-D resistivity responses for a pole-pole array configuration in cross-hole resistivity measurements. Apparent resistivity and secondary potential were computed using the program for a cylindrical inhomogeneity in an uniform host medium excited by a point source of current in a borehole. Surprisingly apparent resistivity in the receiver hole turns out to be lower than the one of surrounding medium regardless of the conductivity of cylindrical inhomogeneity. Using only cross-hole data, therefore, it is impossible to interpret the conductivity of inhomogeneity. To overcome this problem, 3-D measurement and interpretation are necessary. If 3-D data acquisition is impossible, inline data should be used to get the information about the conductivity of inhomogeneity.