• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.225-230
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• 2007

A physical model experiment with GPR and 3-D resisitivity survey were conducted to investigate the geoelectrical response of hydrocarbon-impacted zone, so called smeared zone, on the geophysical data. The results from the experiment show that GPR signals were enhanced when LNAPL was present as a residual saturation in the water saturated system (${\varepsilon}_r$ = 21) due to less attenuation of the electromagnetic energy through the medium, compared to when the medium was saturated with only water (${\varepsilon}_r$ = 21). 3-D resistivity data obtained from the former gas station site demonstrate that the highly contaminated zones could be imaged with low resistivities attributed to the biodegradation of petroleum hydrocarbons at the aged, hydrocarbon-impacted sites. The study results also show that the geophysical methods, as a non-invasive sounding technique, can be a very useful tool for mapping hydrocarbon-contaminated zones.

• Journal of the Korean Geophysical Society
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• v.2 no.3
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• pp.217-224
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• 1999

Although faults can be found by geological surveys, the surface traces of faults are not easily discovered by traditional geological surveys due to alluvia. In and around faults and fracture zones, the electrical resistivity appears to be lower than that of the surroundings due to the content of groundwater and clay minerals. Therefore, electrical resistivity surveys are effective to search buried faults and fracture zones. The dipole-dipole array electrical resistivity surveys, which could show the two dimensional subsurface electrical resistivity structure, were carried out in two areas, Yongdang-ri, Woongsang-eup, Yangsan-si, Kyungsangnam-do and Malbang-ri, Woedong-eup, Kyungju-si, Kyungsangpook-do. The one was next to the Dongrae Fault and the other near the Ulsan Fault was close to the region in which debatable quaternary fault traces had been found recently. From each measured data set, the electrical resistivity cross-section was obtained using the inversion program the reliability of which was analyzed using analytic solutions. A low resistivity zone was found in the inverted cross-section from the Yongdang-ri area survey data, and two low resistivity zones were found in that from the Malbang-ri area survey data. They were almost vertical and were 15∼20 m wide. Accounting the shape and the very low resistivity values of those zones (<100 Ωm)in the inverted section, they were interpreted as fracture zones although they should be proven by trenching. The reliability of the interpretation might be improved by adding some more parallel resistivity survey lines and interpreting the results in 3 and/or adding other geophysical survey.