• Economic and Environmental Geology
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• 제49권3호
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• pp.201-212
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• 2016

Due to growing problems securing stable mineral and energy resources with international political and economic changes, China has dedicated itself to strategies and policies to enhance its stable mineral and energy resources security. China has established a rare earth elements(REE) industry policy after the abolition of the REE exports quota system. China's six large REE companies have also been integrated into REE mining, smelting and refining companies. Efforts have been increased to enhance China's energy security through unconventional oil and gas exploration and development investment, as well as effort in R&D. The country will focus on technology development and exploration to promote commercial production of unconventional oil and gas based on countries with shale gas. China is making long-term contracts and joint ventures to ensure the acquisition of reliable mineral and energy resources from abroad. Government of China has proposed a range of initiatives, such as the integration of resources development strategies and environmental development strategies, internationalization of resource management, supply diversification and advancement, strengthening industry linking strategy, grouping and diversification strategy.

• Journal of Korean Society of Forest Science
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• 제112권3호
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• pp.382-392
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• 2023

Recent reports have indicated a rapid increase in the frequency of sediment disasters due to climate change and other changes in the geological environment. Given this alarming situation and the recent increase in the frequency of land creep in Korea, systematic and efficient recovery and management of land creep areas is essential. The purpose of this study is to identify disaster vulnerability by conducting a physical exploration of land creep in San 4-1, Jayeon-ri, Gaegun-myeon, Yangpyeong-gun, Gyeonggi-do, and examine stability by identifying the overall geological structure of the affected ground. In addition, drilling surveys are conducted to verify the reliability of the measured data. The results of the study reveal that low specific resistance abnormalities are distributed in the upper part of the soil layer and weathering zone and that this section is a 50-120 m exploration line. It is also confirmed to be a low-hardness ground area where tensile cracks are observed. Therefore, there is a need for research focused on developing measures to reduce economic and social damage within the domestic context by continuously monitoring indicators of land creep and identifying land creep risks.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제29권1C호
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• pp.11-20
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• 2009

A new alternative method based on HWAW method to detect underground anomaly was introduced. The location of underground anomaly can be estimated by using 2-dimensional image of phase velocity image with position and wavelength based on distortion phenomena of surface wave due to underground anomaly. Overall procedure of proposed method such as field testing, signal processing and interpretation of the result was introduced. Numerical verification study was performed by using various ground models containing underground anomaly. According to the condition of anomaly, the propagation and reflection characteristics of surface wave were different and this could be more easily shown in the image of phase velocity. Some rules of distortion phenomena were found and these become clues for estimating underground anomaly in interpreting real field data. Field verification tests were performed with conventional geophysical methods such as DC resistivity method and GPR. Though field condition is not homogeneous like numerical models, similar distortion phenomena were found in the testing results and estimated location of underground anomaly was agreed well with the results of another geophysical methods.

• Geophysics and Geophysical Exploration
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• 제3권1호
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• pp.1-6
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• 2000

The 1 $km^2$ area studied is located in Sukchun-ri, Hwasung-koon, the southern part of Kyeonggi-do. Even though this site has been known as a contaminated area caused by seawater intrusions, geophysical and geochemical surveys have never been carried out at the site to determine the extent of the seawater contamination and to investigate whether the seawater intrusion is in progress. The purpose of this study is to determine the extent of seawater contamination and a preferred channel of the seawater intrusion using geophysical methods such as DC resistivity surveys with Schlumberger array and a dipole-dipole array. In order to determine whether the seawater intrusion is in progress in the area, DC resistivity monitoring with Schlumberger array was performed. According to the resistivity map obtained from the inversion of the resistivity data measured with Schlumberger array, the study area is divided into two districts as relatively lowly resistive (less than 30 ohm-m) and highly resistive (more than 30 ohm-m) areas. The distribution of the lowly resistive area is consistent with the distribution of the layer composed of clay minerals, and the resistivity of this layer decreases slowly as approaching to the old seashore. Hydrogeological analysis shows that the clay layer within a distance of about 200 m from the seashore has been already contaminated by sea-water and its electric conductivity is 8 times higher than that of the sand layer covered by the clay layer. According to the results of the 2-dimensional DC resistivity surveys with a dipole-dipole array, there are two preferred channels of the seawater intrusion in the site, and both the channels are in the NW-SE direction from the old seashore. The lowly resistive zone in the southern channel extends to a depth of 80 m. The DC resistivity monitoring with Schlumberger array was carried out along the preferred channel which has the low resistivity Bone (fracture zone) that extended to a depth of 80 m. The time series of apparent resistivity, measured at a distance of 260 m from the old coast line, fluctuates with a period of 12 hours. From these observations, it can be concluded that the seawater intrusion caused by tidal action is still in progress along the fractured zone interpreted by the DC resistivity surveys with a dipole-dipole array.

• Economic and Environmental Geology
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• 제39권6호
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• pp.711-717
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• 2006

In order to study gas hydrate, potential future energy resources, Korea Institute of Geoscience and Mineral Resources has conducted seismic reflection survey in the East Sea since 1997. one of evidence for presence of gas hydrate in seismic reflection data is a bottom simulating reflector (BSR). The BSR occurs at the interface between overlaying higher velocity, hydrate-bearing sediment and underlying lower velocity, free gas-bearing sediment. That is often characterized by large reflection coefficient and reflection polarity reverse to that of seafloor reflection. In order to apply depth migration to seismic reflection data. we need high performance computers and a parallelizing technique because of huge data volume and computation. Phase shift plus interpolation (PSPI) is a useful method for migration due to less computing time and computational efficiency. PSPI is intrinsically parallelizing characteristic in the frequency domain. We conducted conventional data processing for the gas hydrate data of the Ease Sea and then applied prestack depth migration using message-passing-interface PSPI (MPI_PSPI) that was parallelized by MPI local-area-multi-computer (MPI_LAM). Velocity model was made using the stack velocities after we had picked horizons on the stack image with in-house processing tool, Geobit. We could find the BSRs on the migrated stack section were about at SP 3555-4162 and two way travel time around 2,950 ms in time domain. In depth domain such BSRs appear at 6-17 km distance and 2.1 km depth from the seafloor. Since energy concentrated subsurface was well imaged we have to choose acquisition parameters suited for transmitting seismic energy to target area.

• Geophysics and Geophysical Exploration
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• 제16권4호
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• pp.240-249
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• 2013

The seismic data quality of marine geological and engineering survey deteriorates because of the sea swell. We often conduct a marine survey when the swell height is about 1 ~ 2 m. The swell effect correction is required to enhance the horizontal continuity of seismic data and satisfy the resolution less than 1 m. We applied the swell correction to the 8 channel high-resolution airgun seismic data and 3.5 kHz subbottom profiler (SBP) data. The correct sea bottom detection is important for the swell correction. To detect the sea bottom, we used maximum amplitude of seismic signal around the expected sea bottom, and picked the first increasing point larger than threshold value related with the maximum amplitude. To find sea bottom easily in the case of the low quality data, we transformed the input data to envelope data or the cross-correlated data using the sea bottom wavelet. We averaged the picked sea bottom depths and calculated the correction values. The maximum correction of the airgun data was about 0.8 m and the maximum correction of two kinds of 3.5 kHz SBP data was 0.5 m and 2.0 m respectively. We enhanced the continuity of the subsurface layer and produced the high quality seismic section using the proper methods of swell correction.

• The Journal of Engineering Geology
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• 제23권4호
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• pp.457-465
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• 2013

We integrated and correlated datasets from surface and subsurface geophysics, drilling cores, and engineering geology to identify geological interfaces and characterize the joints and fracture zones within the rock mass. The regional geometry of a geologically weak zone was investigated via a fence projection of electrical resistivity data and a borehole image-processing system. Subsurface discontinuities and intensive fracture zones within the rock mass are delineated by cross-hole seismic tomography and analyses of dip directions in rose diagrams. The dynamic elastic modulus is studied in terms of the P-wave velocity and Poisson's ratio. Subsurface discontinuities, which are conventionally identified using the N value and from core samples, can now be identified from anomalous reflection coefficients (i.e., acoustic impedance contrast) calculated using a pair of well logs, comprising seismic velocity from suspension-PS logging and density from logging. Intensive fracture zones identified in the synthetic seismogram are matched to core loss zones in the drilling core data and to a high concentration of joints in the borehole imaging system. The upper boundaries of fracture zones are correlated to strongly negative amplitude in the synthetic trace, which is constructed by convolution of the optimal Ricker wavelet with a reflection coefficient. The standard deviations of dynamic elastic moduli are higher for fracture zones than for acompact rock mass, due to the wide range of velocities resulting from the large numbers of joints and fractures within the zone.

• Journal of the Korean earth science society
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• 제27권1호
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• pp.83-94
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• 2006

The objective of this paper is to extract and analyze the sediment environment change information in the Sachencheon, Gangneung, Korea that was seriously damaged as a result of typhoon Rusa aftermath early in September, 2002 using multi-temporal remote sensing data. For the extraction of change information, an unsupervised approach based on the automatic determination of thresholding values was applied. As the change detection results, turbidity changes right after typhoon Rusa, the decrease of wetlands, the increase of dry sand and channel width and changes of relative level in the stream due to seasonal variation were observed. Sedimentation in the cultivated areas and restoration works also affected the change near the Sacheoncheon. In addition to the change detection analysis, several environmental thematic maps including microtopographic map, distributions of estimated amount of flood deposits and flood hazard landform classification map were generated by using remote sensing and field survey data. In conclusion, multi-temporal remote sensing data can be effectively used for natural hazard analysis and damage information extraction and specific data processing techniques for high-resolution remote sensing data should also be developed.

• Tunnel and Underground Space
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• 제22권6호
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• pp.412-428
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• 2012

To achieve mine development, a large amount of data concerned with the geological structure and the ore body had to be investigated and collected through geological survey, drilling and geophysical explorations. In most previous cases, however, the data were usually analyzed two dimensionally and those results showed some limits because of their 2D presentation. Those 2D maps such as geological plane sections or longitudinal sections cause lots of difficulties in understanding the complex geological structure or the feature of ore body in a spatial way. In this study, research area was set on the abandoned Yangyang iron mine in Korea and the Sugaeng ore body within the mine was selected as the research target to design a mine haulage system for reopening. A 3D mine model of this area was tried to be constructed using a 3D modelling software, GEMS. An accurate 3D model including the ore body, the geological structure, the old underground mine drifts and the new mine drifts was constructed under the purpose of reopening of the abandoned iron mine. Especially, mine design for trackless haulage system was conducted. New inclines and drifts were planned and modelled 3 dimensionally considering the utilization of old drifts and shaft. In addition to the 3D modelling, geostatistical technique was adopted to generate a spatial distribution of the ore grade and the rock physical properties. 3D model would be able to contribute in solving problems such as evaluating ore reserves, planning the mine development and additional explorations and changing the development plans, etc.

• Geophysics and Geophysical Exploration
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• 제6권3호
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• pp.126-133
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• 2003

High-resolution shallow marine seismic surveys have been carried out for the resources exploration, engineering applications and Quaternary mapping. To improve the resolution of subsurface structure image, multichannel digital technique has been applied. The quality of the image depends on the vertical and horizontal resolution and signal to noise (S/N) ratio which are associated with the data acquisition parameters such as sample interval, common midpoint (CMP) interval and CMP fold. To understand the effect of the acquisition parameters, a test survey was carried out off Yeosu and the acquired data were analyzed. A 30 $in^3$ small air gun was used as a seismic source and 8 channel streamer cable with a 5 m group interval was used as a receiver. The data were digitally recorded with a shot interval of 2 s and sample interval of 0.1 ms. The acquired data were resampled with various sample intervals, CMP intervals and CMP folds. The resampled data were processed, plotted as seismic sections and compared each other. The analysis results show that thin bed structure with ${\~}1m$ thickness and ${\~}6^{\circ}$ slope can be imaged with good resolution and continuity and low noise using the acquisition parameters with a sample interval shorter than 0.2 ms, CMP interval shorter than 2.5 m and CMP fold more than 4. Because seismic resolution is associated with the acquisition parameters, the quality of the subsurface structure can be imaged successfully using suitable and optimum acquisition parameters.