• Geophysics and Geophysical Exploration
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• v.9 no.2
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• pp.163-170
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• 2006

The shortage of proven hydrocarbon reserves has resulted in exploration progressing from the offshore into progressively deeper water of the continental shelf. Despite the success of seismic acquisition at ever greater depths, there are marine geological terrenes in which the interpretation of seismic data is difficult, such regions dominated by scattering or high reflectivity that is characteristic of carbonate reefs, volcanic cover and submarine permafrost. A marine controlled-source electromagnetic (CSEM) method has recently been applied to the oil and gas exploration thanks to its high-resistivity characteristics of the hydrocarbon. In particular, this method produces better results in terms of sensitivity under the deep water environment rather than the shallow water. Only in the last five years has the relevance of CSEM been recognized by oil companies who now use it to help them make exploration drilling decisions. Initial results are most promising and several contractors now offer magnetotelluric and CSEM services.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.180-183
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• 2003

Recently, the pollution of soil and groundwater becomes a serious social problem, and geophysical exploration methods have been introduced as a remedial investigation method of subsurface. Digital technologies such as personal computer have revolutionized our ability to acquire large volumes of data in a short term, and to produce more reliable results for subsurface image. Also, color graphics easily visualizes the survey results in a more understandable manner, and it is widely used for not only characterizing the contaminated subsurface but also monitoring contaminant and remedial process. In this paper, electrical resistivity survey were carried out In order to understand characteristics of waste landfills, and the applicability of geophysical prospecting to site assessment of waste landfill was also tested. According to the result, electrical resistivity survey were effective in estimating distribution of the leachate plume.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.273-278
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• 2007

2-D MT surveys at the Century mine in Australia have been performed with very far remote reference in Esashi, Japan as well as Gregory Downs, which are roughly 6400 km and 80 km apart from the field site, respectively. Long period pulsations observed in this survey generally showed dominant $H_x$ polarization than $H_y$; $H_x$ component is more than 3 times stronger than $H_y$ component. Polarity reversal in magnetic field pointing east ($H_y$ component) has also been observed in long period pulsations, while $H_x$ component remain coherent between the hemispheres. Though $H_x$ component shows relatively good coherency than $H_y$ component between the hemispheres at frequencies lower than 0.01 Hz, it seems rather too far to be used as a remote reference for ordinary MT frequency band.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.279-284
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• 2007

The cultural noise sources in magnetotellurics were localized using the source localization method. Conventional beamforming techniques are not applicable for electromagnetic source localization. In this study, the matched field processing and genetic algorithm are used to localize an electromagnetic source and estimate the polarization direction. The source localization using MT field data shows the characteristics of estimated source distribution related to the strength of cultural noise.

• Journal of the Korean Geosynthetics Society
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• v.18 no.3
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• pp.79-88
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• 2019

This study described a results of groundwater injection test in cavity, in order to evaluate characteristics of cavity expansion under pavement. That is, groundwater amount proportional to the cavity volume was injected into the generated cavity step by step, and then the cavity with the changed size was monitored as the injected groundwater was drained. The test result showed that the cavity volume by groundwater injection increased, and then it converged or decreased. This means that some of the relaxation soil around the cavity collapsed, and the fine-grained soils in some soils filled the void in the surrounding soils when the cavity is expanded by groundwater injection. The volume change and expansion characteristics of the cavity according to the groundwater injection step were analyzed. The result showed that the cavity extended laterally. Therefore, it was found that the cavity expansion is caused by the repetition of the relaxation soil collapse due to the groundwater flow and the loss of the collapsed soil below the cavity.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.123-127
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• 2005

Surface refraction and crosswell seismic survey conducted as a part of geoscientific studies applied in an area of ground water reservoir shows that, 1) the average velocity with respect to depth is about 250 m/s for the surface layer (<4m), 2,500 m/s for the weathered formation, and greater than 3,500 m/s for the bed rocks, 2) the depth to the bedrock derived from the seismic studies and the sonic log (17m) is somewhat different from the depth obtained from the core study (25m).

• 한국지구물리탐사학회:학술대회논문집
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• 2000.09a
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• pp.5-18
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• 2000

토양${\cdot}$지하수환경분야와 관련된 제도들이 최근 개정 움직임을 보이고 있는 시점에서 조사단계 및 처리단계이후의 유지관리분야에서 지구물리탐사분야의 중요성이 점차 인식되고 있다. 특히 토양${\cdot}$지하수오염과 관련하여 오염유발가능시설의 $80\%$가 농촌지역에 산재되어 있으나, 그 규모와 오염정도에 대한 조사가 제대로 이루어지지 않은 상태이다. 이에 따라 지하수의 수질은 점차적으로 저질화 되어가고 있으나 비가시적인 이유로 인하여 그동안 소홀히 다루어져 왔다. 또한 오염조사 및 오염복원 등이 제도적으로 뿌리내리지 못해 오염원의 범위, 정도 등을 확인하는데 많은 한계점을 드러내고 있는 현실이다. 최근 관계법령의 개정을 통해 보다 엄격하고 강화된 규제 및 책임을 법제화하는 일은 현재와 미래의 환경보전을 위해 다행한 일이라 하겠다. 특히, 지하수오염 등은 국가적인 불행한 일이므로 향후 토양${\cdot}$지하수환경에 막대한 영향을 미칠 오염인자에 대한 정밀실태조사가 시급히 이루어져야 할 것이다. 따라서 현재 개정을 추진하고 있는 토양환경보전법과 지하수법의 개정취지를 제대로 살리면서 환경오염에 능동적으로 대처하기 위하여 지구물리탐사분야와 지질조사분야에서의 다양하고 정밀한 조사를 위한 방법들과 내용에 대한 연구가 절실히 요구되고 있다. 또한 이와 더불어 오염부지 특성조사를 위한 절차 및 방법들이 구체적으로 법제화되어 할 것이다.

• Geophysics and Geophysical Exploration
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• v.7 no.1
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• pp.99-104
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• 2004

A combination of drilling, geophysical well logging, and electrical soundings was performed to evaluate seawater intrusion in Baeksu-eup, Youngkwang-gun, Korea. The survey area extends for over 24 $km^2$. To delineate the extent of seawater intrusion, 60 vertical electrical soundings (VES) have been carried out. Twelve wells were also drilled for the collection of hydrogeological, geochemical, and geophysical well logging data, to delineate the degree and vertical extent of seawater intrusion. To map the spatial distribution of seawater in this coastal aquifer, geophysical data and hydrogeochemical results were used, and the relation between the resistivity of groundwater and equivalent NaCl concentration was found. Layer parameters derived from VES data, various in-situ physical properties from geophysical well logging, and the estimated equivalent NaCl concentration were very useful for quantitative evaluation of seawater intrusion. Our approach for evaluating seawater intrusion can be considered a valuable attempt at enhancing the use of geophysical data.

• Economic and Environmental Geology
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• v.38 no.4 s.173
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• pp.395-409
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• 2005

To explore submarine groundwater discharge (SGD) into the coastal zone of Jeju Island, the water quality analysis with seasonal remotely sensed data was carried out. If the groundwater is directly discharged into the ocean, the water quality of coastal zone is influenced. Therefore sea surface temperature (SST), the transparency, and Chlorophyll-a's concentration were analyzed for extracting the anomaly zone related with SGD using Landsat Thematic Mapper (TM) data acquired on April, August, and December. Then the spatial characteristics of springs, which located along the coastal area, were analyzed by CIS data integration based on Fuzzy logic. The integration results were compared with the anomaly zone extracted from Landsat TM data, and it is considered that springs has close relationship with SGD.

• Geophysics and Geophysical Exploration
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• v.6 no.1
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• pp.7-12
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• 2003

The lineament extraction from satellite images is important in the geologic studies including groundwater and mineral exploration, groundwater survey, natural hazard analysis, and many others. The lineaments in remote sensing images are identified by the difference of pixel values or brightness. Since the visual interpretation is apt to be influenced by the knowledges and experiences, many of the automatic lineament detection algorithms are developed to ensure the objectives and efficient outputs. DSTA (dynamic segment tracing algorithm) is one of such algorithms, which can be applied to not only mountainous area but also alluvial area. However, when the alluvial area is wider than mountain region, somewhat severe noises are generated. To reduce such noises, AERA (alluvial effect reducing algorithm) is proposed and tested for the image which contains mountains, cultivated land and urban area. Upon the application of AERA, alluvial effects in lineament extraction from satellite image are substantially reduced.