• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.107-112
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• 2007

To establish the reinforce region and technique through the embankment dike after identifying the region of seawater inflow, we carried out small-loop electromagnetic (EM) survey, electrical resistivity survey and refraction seismic method. We also analyzed the distribution of electrical conductivity in reservoir with depth every two month and monitored water level variations with tidal variation in four observation wells located at seaside and reservoir side in order to analyze the relationship with survey results. From both the cross-correlation between tidal and water level variation at four wells and the distribution of electrical conductivity in reservoir with depth, the major portion of seawater inflow are identified through the embankment dike. From electromagnetic and electrical resistivity survey results, it was found that the seawater inflow were happened through several small regions at seaside and became wider near reservoir side. The 2-D inversion sections of refraction seismic method showed that the pebble-bearing sand layer is spread over the whole region with two to four width. From the this study, small-loop EM, electrical resistivity and refraction seismic surveys accompany with the distribution of electrical conductivity in reservoir with depth and the monitoring results for water level variations are revealed to be effective to identify seawater inflow pathway through embankment dike and to establish the reinforce region and technique through the embankment dike.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.517-523
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• 2007

Geophysical surveys(seismic refraction, electrical resistivity, and ground penetrating radar) were performed to delineate the weathering zone associated with vadose water in Chojeong area and investigate the fault related fracture zones. On the basis of seismic velocity structures, weathering layer for the southwestern part is interpreted to be deeper than for the northeastern part. The depth to bedrock(i.e., thickness of weathered zone) from seismic refraction data attempted to be correlated with drill-core data and groundwater level. As for the investigation of geological discontinuities such as fault related fracture zone, seismic refraction, electrical resistivity, and ground penetrating data are compositely employed in terms of velocity and resistivity structures for mapping of surface boundary of the discontinuities up to shallow depth. Surface boundaries of fracture zone are well indicated in seismic velocity and electrical resistivity structures. Accurate estimation of weathered zone and fracture zone can be successfully available for mapping of attitude of vadose water layer.

• Journal of the Korean Geophysical Society
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• v.4 no.1
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• pp.11-20
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• 2001

Seismic refraction and electrical resistivity surveys were conducted in Bangeosan Maaebul site located in Haman, Kyungnam, in order to present geophysical safety analysis method for masonry cultural properties. Seismic refraction exploration revealed that the ground was composed of three layers in term of seismic wave velocity; the upper, medium, and lower layers. The low velocity ranging from 308 to 366 m/sec in upper layer suggests weathered soil, the intermediate velocity from 1906 to 2090 m/sec in the medium layer indicates weathered rocks, and the high velocity from 5061 to 5650 m/sec in the lower layer implies extremely hard rocks. Our seismic result suggests that the upper and medium layer around the Maaebul should be reinforced to support the construct. The result of electric resistivity survey shows that there exists a low resistivity zone, ranging from 131 to 226 Ohm-m, at the right side of the Maaebul with the direction of NE-NNE. This area is the weakness zone as it plays role of the underground water passage in rainy season.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.446-449
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• 2004

High resolution geophysical imaging to delineate costal aquifer and seawater- freshwater interface has been applied in Baesu-eup, Yeonggwang-gun, Jeolla province Electrical resistivity information from vertical electrical sounding and 2-D electrical resistivity survey is key parameter to map equivalent Nacl concentration map over the survey area. Seismic velocity from refraction tomographic survey, on the other hand, gives more reliable information on the subsurface stratagraphy than electrical resistivity methods which frequently suffer from low resolution due to masking effect. We imaged high-resolution 3-D structure of costal aquifer by correlating the electrical resistivity with seismic velocity, and mapped equivalent NaCl concentration map using resistivity and hydro-geological information from well logging.

• Journal of the Korean Geophysical Society
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• v.2 no.1
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• pp.75-88
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• 1999

A recent major subject of geophysical exploration is research into 3-D subsurface imaging with a composite information from the various geophysical data. In an attempt to interpret Schlumberger sounding data for the study area in 2-D and 3-D view, resistivity imaging was firstly performed and then pseudo-3-D resistivity volume was reconstructed by interpolating several 1-D resistivity plots. Electrical resistivity discontinuities such as fracture zone were successfully clarified in pseudo-3-D resistivity volume. The low resistivity zone mainly associated with fracture zone appears to develop down to granitic basement in the central part of the study area. Seismic velocity near the lineament is estimated to be approximately as small as 3,000 m/s, and weathering-layer for the southeastern part is interpreted to be deeper than for the northwestern part. Geophysical attributes such as electrical resistivity, seismic velocity, radioactivity for the Chojeong Area were analysed by utilizing a GIS software Arc/Info. The major fault boundaries and fracture zones were resolved through image enhancement of composite section (electrical resistivity and seismic refraction data) and were interpreted to develop in the southeastern part of the area, as characterized by low electrical resistivity and low seismic velocity. However, radioactivity attribute was found to be less sensitive to geological discontinuities, compared to resistivity and seismic velocity attributes.

• Journal of the Korean Geophysical Society
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• v.5 no.4
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• pp.329-336
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• 2002

Electrical resistivity dipole-dipole, seismic refraction, and seismic reflection methods were performed to delineate the boundaries the Yongdong basin(Cretaceous) in terms of physical properties and to ultimately identify the margin architectures of the faults or unconformities. Higer resistivities (approximately >2000 ohm-m) most likely originate from the basement of the basin, contrasting with the lower resistivities from infilled sedimentary rocks. Faults at the eastern margin and unconformities at the western boundary are characterized as high-slope($70^{\circ}$) and gentle-slope($30^{\circ}$) gradients in the resistivity sections, respectively Such features for the boundaries are also suggested by the lower values of seismic velocity and resistivity for the western margin.

• Journal of Industrial Technology
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• v.20 no.A
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• pp.285-293
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• 2000

In 1970's, the analysis of shallow substructure was the interests of geological engineering and environmental problems. And seismic refraction method was applied to detect those structures. From 1980's, digital electric industry is rapidly developed and high resolution prospecting equipment is supplied. And seismic reflection method is applied to achieve various data gathering and data analysis. In this study, geophysical prospecting method is applied to calculate the basic data of limestone yield production. Seismic shallow reflection method is used to detect the depth of bedrock and electrical resistivity method is used to detect of limestone layer boundary.

• The Journal of Engineering Geology
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• v.19 no.1
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• pp.1-8
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• 2009

Geophysical surveys were conducted on an upper part of a natural slope located at Daejeon University. Electrical resistivity and seismic refraction measurements were carried out to obtain information on a weathered zone and internal structure at shallow depth, while AMT measurement a bed rock and geological structure at deep depth. With all the techniques applied, these results show a good correlation between electrical resistivity images and refraction velocity distributions for the characterization of a weathering and geological structure at depth. In particular, AMT survey seems to be the powerful tool for detecting a distribution of a bed rock with deep depth. The combined geophysical investigation produced a detailed image of a subsurface structure and improved well in the interpretation.

• Journal of the Korean Geophysical Society
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• v.3 no.1
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• pp.57-66
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• 2000

The location and geometry of the Ulsan Fault play important roles in interpreting tectonic evolution of the southeastern part of the Korean Peninsula. Dipole-dipole electrical resistivity surveys and seismic refraction surveys were carried out in the Yaksoo area, Ulsan in order to measure the thickness of the alluvium covering the Ulsan Fault and to find associated fracture zones and possibly the location of its major fault plane. The collected data were analyzed and interpreted. Some results reported previously by others were also used in this interpretation. No low resistivity anomalies were found in the cross-sectional resistivity image of the survey line located in the east of the Dong River. In contrast, well-developed continuous low resistivity anomalies were detected in the west of the Dong River. This strongly suggests that the major fault plane of the Ulsan Fault is located under or in the west part of the Dong River. Two refraction boundaries corresponding to the underground water level and the bottom of the alluvium were found by refraction surveys carried out on the limited part of the east survey line. The thickness of the alluvium was found to be about 30 m. Small faults in the basement rock identified by reflection surveys were not detected by both resistivity and refraction seismic surveys. This might be explained by assuming that low resistivity anomaly is more closely related to the clay contents than the water contents. On the other hand, it may be resulted by the limited resolution of the resistivity and refraction surveys. Detailed study is required to clarify the reason. Resistivity survey is frequently considered to be a good exploration method to detect subsurface faults. However, it appears to be less useful than reflection seismic survey in this work. In dipole-dipole resistivity survey, the number of separation should be increased to survey deeper subsurface with the same resolution. However, signal to noise ratio decreases as the number of separation increases. In this survey area, the signal to noise ratio of up to sixteen separations was good enough based on the statistical properties of measurements.

• Journal of the Korean Geotechnical Society
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• v.38 no.10
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• pp.49-60
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• 2022

Underground urbanization appears to be a promising solution in response to the shortage of construction sites in the above-ground space. In this context, an accurate evaluation of a construction site ensures the long-term performance of geosystems. This study characterizes potential sites for complex plants built in underground space using geophysical methods (i.e., seismic refraction exploration and electrical resistivity survey) and in situ tests (i.e., standard penetration tests (SPTs) and downhole tests). SPTs are conducted in nine boreholes BH-1-BH-9 to estimate the groundwater level and vertical distribution of geological structures. The seismic refraction method enables us to obtain the elastic wave velocity and thickness of each soil layer for each cross-sectional area. An electrical resistivity survey conducted using the dipole array method provides the electrical resistivity profiles of the cross-sectional area. Data obtained using geophysical techniques are used to assess the classification of the soil layer and bedrock, particularly the fracture zone. This study suggests that geotechnical information using in situ tests and geophysical methods are useful references to design an underground complex plant construction.