• KCID journal
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• v.13 no.2
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• pp.254-261
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• 2006

We applied electrical resistivity survey using modified pole-pole array and small-loop electromagnetic survey to delineate the zone of seawater inflow through a tide embankment. The tide embankment is generally affected by tidal variation and has low resistivity characteristic due to the high saturation of seawater. For this reason, the electrical resistivity survey using modified pole-pole array, which is relatively more effective to the conductive media, was carried out to detect the inflow zone of seawater and small-loop electromagnetic survey using multi-frequency with 300 to 20,010 Hz was conducted. As a result of both electrical resistivity survey using modified pole-pole array and small -loop electromagnetic survey, these survey methods are found to be quite effective for investigation of seawater inflow zone in the sea dike.

• Geophysics and Geophysical Exploration
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• v.27 no.1
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• pp.69-83
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• 2024

Considering importance and specificity, site investigations for deep geological disposal of Spent Nuclear Fuel require stringent quality control, unlike general geotechnical investigations for tunnels and bridges. In this study, we present a case of selecting geophysical survey method for individual site investigation stage and preparing geophysical survey guideline. The proposed geophysical survey guidelines include procedures, considerations, and quality control for exploration planning, data acquisition, data processing, and interpretation. They comprehensively summarize the contents of airborne electromagnetic survey and seismic reflection survey.

• Economic and Environmental Geology
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• v.46 no.2
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• pp.105-121
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• 2013

This study introduces integrated approach on detection of a leakage in a sea wall based on remote sensing, electric resistivity survey, electromagnetic survey, and borehole survey for the Seosan A-Region sea wall. The satellite temperature distribution from Landsat ETM+ data identifies water leakage distribution and period by analyzing temperature mixing patterns between sea water and fresh water. Electric resistivity survey provides both horizontal and vertical anomaly distributions over the sea wall showing below average electric resistivity. Electromagnetic survey(electrical conductivity survey) reveals the potential possible leakage areas with minimal background impact by comparing electrical conductivity values between high and low tides. Borehole image processing system confirmed the locations of anomalies identified from the other survey methods and distributions of vertical fracture zones. The integrated approach identified 41.7% of the sea wall being the most probable area vulnerable to water leakage and effectively approximated both horizontal and vertical distribution of water leakage. The integrated analysis of remote sensing, electric resistivity survey, electromagnetic survey and borehole survey is considered to be an optimal method in identifying water leakage distribution, period, and extent of fractures knowledged from the boreholes.

• Economic and Environmental Geology
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• v.33 no.6
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• pp.525-536
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• 2000

Electromagnetic and electric surveys were performed to reveal the deep structure of the Yangsan fault in the Bong-gye and Unyang areas, Kyeongnam Province, Korea. Especially, high-frequency magnetotelluric (HFMT) method of EM survey was mainly employed to study the deep subsurface configuration of Yangsan fault. HFMT survey was performed at 25 points of spacing 50 m, making 1.3 km survey line in Unyang area and 13 points of spacing 50 m, making 0.6 km survey line in Bong-gye area. Two 2-D cross-sections (Unyang and Bong-gye areas) were achieved as results. Electric survey by dipole-dipole array was performed to study the structure of shallow subsurface and compare the results with HFMT surveys. The results of HFMT and electric surveys show that Yangsan fault is a geologic boundary. It is very narrow and steep (about $80^{\circ}C$), and extends to 1~1.5 km depth.

• Journal of Korean Elementary Science Education
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• v.23 no.3
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• pp.182-191
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• 2004

In this research a questionary survey was implemented to investigate how elementary school students in $3^{rd}-6^{th}$ grade understood articles or terminology using electromagnetic wave technology in contemporary culture. Also, part of students who had participated in questionnaire survey was interviewed 2 times for each 20 minute personally to investigate students＇ perceptions about some household articles in their every day life using electromagnetic wave technology. As a result, first, elementary school students had pretty higher perceptions of the artificial satellite provided in their curriculum and the technology of electromagnetic wave released from cartoons, computer games or advertisements. Second, because they were concerned about appearances of household articles, they perceived some household articles in their every day life with conceptions of electricity or visual mechanism.

• Geophysics and Geophysical Exploration
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• v.7 no.4
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• pp.251-255
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• 2004

Electric cables such as multi-interphone cables and ribbon cab]os are commonly used for data aquisition in the DC resistivity survey. In general, electromagnetic induction may occur in the electric cables when electric current flows through them. In case of using multi-interphone cables in the DC resistivity survey, electromagnetic induction could take place due to the entangled wires of the multi-interphone cables, when the current flows through them. Then, the electromagnetic induction may cause measured DC resistivity data to be distorted. In this study, a monitoring system with PXI (PCI Extention for Instrumentation) was constructed to examine signal distortion on the DC resistivity data, attributed to the electromagnetic induction. Common electric cables used in the DC resistivity survey were tested to observe the waveforms of the electric voltages. The waveforms measured were compared to examine signal distortion due to the electromagnetic induction. The results may provide information on the resistivity data obtained using different electric cables in the DC resistivity survey. The distortion of waveforms attributed to the electromagnetic induction wat not observed when using ribbon cables for DC resistivity data aquisition, while the distortion were observed when using multi-interphone. Therefore, the ribbon cables provide better quality of data than other cables in the DC resistivity data aquisition.

• Economic and Environmental Geology
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• v.32 no.2
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• pp.161-167
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• 1999

Electric and electromagnetic surveys were conducted to investigate the deep structure of the Ulsan fault in Ipsil area, south of Kyeongju. On this study, especially high-frequency magnetotelluric method of electromagnetic survey in the frequency range of 10~100,000 Hz was mainly employed to study the deep subsurface configuration. High-frequency MT survey was performed at 70 points of spacing 30~50 m, making 3.8 km survey line. As a survey result, a 2-km-depth 2-D cross-section was achieved. It shows vertical and horizontal subsurface variations of resistivity values. Near-surface layer having low resistivity value becomes thicker eastward up to 800m. There is a steep low resistivity zone in the west side of survey line, and there exists two low resistivity zones dipping west in the east side of survey line. Two low resistivity zones are interpreted to be related to major movement pattern of the Ulsan fault. This suggests that major fault lines are developed on both peripheral sides of the broad fault zone.

• Journal of the Korean Geotechnical Society
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• v.31 no.11
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• pp.41-48
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• 2015

An investigation of a void and a loose layer of the ground is essential in order to prevent the losses of life and properties caused by subsidence and sinkage of the ground. Recently, studies on the ground penetrating radar survey have been actively conducted in order to estimate the void and the loose layer of the ground. However, an error can be committed by contrarily predicting a dense ground and a loose layer because the ground penetrating radar estimates an interface depth between geo-materials that have different electrical impedances. In this study, a loose ground depth is estimated using the characteristics of the reflected electromagnetic wave obtained from the ground penetrating radar survey. To gather the signals according to the loose ground depths, the ground penetrating radar survey is conducted on a field which underwent a huge ground settlement. In addition, the dynamic cone penetration test is performed to verify the result of the loose ground depth estimation from the ground penetrating radar survey. From the analysis of the reflection characteristics of the electromagnetic wave, a phase of an electromagnetic wave reflected from a denser soil layer is found to be identical with that of the first measured signal. On the other hand, a phase of an electromagnetic wave reflected from the loose soil layer is found to be opposed to that of the first detected signal. The comparison between the dynamic cone penetration index and electromagnetic signals by the ground penetrating radar shows that the estimated depth of the loose or dense layer is perfectly matched with a high reliability. The ground penetrating radar survey and the signal analysis performed in this study can be used not only for the survey of interface depth between the discontinuity layers but also for the estimation of the loose layer.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.3
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• pp.39-47
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• 1999

This paper presents the survey of technical trend in AD converters for wireless communication systems. This paper provides explanations about the performance measure of ADC in wireless communication application and the relation ship between BER versus effective resolution and sampling speed. The survey suggests that at least one step analog frequency down conversion is required for software defined radio systems due to current technological limit.

• Economic and Environmental Geology
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• v.39 no.4 s.179
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• pp.427-440
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• 2006

Electromagnetic(EM) survey has been in use for over a half century as a standard routine for, mineral exploration in many parts of the world. But EM survey work and serious research effort were initiated in Korea only as late as in early 1980s, largely inspired by four pioneers who did their graduate studies in the U.S.A. in 1970s. Nevertheless domestic achievements in the field of EM survey are remarkable in the last two decades: the field operations and related interpretational skills appear to have reached a global standard, even compared with the most advanced in other countries, virtually in a whole spectrum of the method which includes magneto-tellurics(MT), Controlled Source Audio-frequency Magneto-tellurics(CSAMT), geomagnetic sounding, small loop survey systems, Very Low Frequency(VLF), Ground Penetrating Radar(GPR), time domain surveys, and noise analysis. Besides mineral exploration, EM survey has been applied in Korea to hydrogeology, geotechnical engineering, non-destructive investigation of structures, unexplored ordnance(UXO) investigation, environmental monitoring, and archaeological investigation as well. Now that original contributions of several Korean geophysicists are found even in new frontiers such as high-frequency EM survey, investigation in time-domain EM field for buried metal objects and structures, and also modem data inversion scheme, it is duly hoped that they make some technical breakthrough to unravel still entangled knots of EM survey method in a forseeable future.