• Economic and Environmental Geology
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• v.48 no.1
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• pp.77-88
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• 2015

Advanced geological surveys and exploration activities were first carried out in Korea in 1884 in accordance with a treaty of friendship and commerce between Great Britain and Korea and a treaty of friendship and commerce between Germany and Korea. The first paper by Gottsche, C. was also published in a German Journal in 1886. Efforts toward independent acquisition of Western geological survey and exploration technology were actively promoted by the Korean Empire in the early 1900s, but were frustrated by the Japanese Empire. Systematic geological surveys and exploration were conducted in Korea by Japanese geologists during the Japanese occupation. A basic geological maps(61sheets), a bulletin on the geological survey of Korea, a bulletin and technical report on deposits in Korea, and a coalfield geological survey report were published during this period. Overall, the intentions under lying the geological surveys and exploration activities by foreigners in Korea prior to the Japanese occupation were questionable. However, the results of these surveys and explorations themselves can be evaluated as positive in terms of academic performance.

• Economic and Environmental Geology
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• v.48 no.5
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• pp.401-408
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• 2015

The achievements of Tateiwa Iwao's work in Korea are assessed as follows. Firstly, he pioneered the practice of stratigraphy in the Korean peninsula and completed geological maps of 21 sheets at 1:50,000 scale. Secondly, he published the results of a geological survey as bulletins, technical reports, and papers. Thirdly, he faithfully carried out the handover of assets and research outputs to Korea. Finally, after returning to Japan, Tateiwa wrote a book entitled The Korea-Japanese Tectonic Zone: History of a Geological Survey in Korea. However, he neglected to educate and train the next geologists for conducting geological surveys and exploration in Korea.

• Geophysics and Geophysical Exploration
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• v.7 no.1
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• pp.1-6
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• 2004

High-resolution S-wave reflection surveying has been successfully conducted on paved areas using a Land Streamer originally designed by the author. The main feature of the Land Streamer tool is the non-stretch woven belt on which geophone units are mounted to form a multichannel geophone array similar to a marine streamer. Because it is easily towed by a vehicle or by hand, the tool leads to high performance in field measurements and resultant cost-effectiveness of high-resolution reflection surveys. Although each geophone unit is coupled to the pavement through a metallic baseplate instead of being firmly planted in the ground, the Land Streamer tool provides comparatively clean data, unaffected by traffic noise even on the pavement. Thus, the tool is capable of expanding the opportunity for S-wave reflection surveys in urban areas where many surfaces are paved and traffic noise is severe. A series of high-resolution S-wave reflection surveys on paved areas delineated detailed structures of surface layers shallower than 60 m, and proved the wide applicability of the tool to engineering, environmental applications, and earthquake disaster prevention projects.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.422-431
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• 2003

Helicopter-borne electromagnetic (HEM) systems were originally developed for the exploration of mineral deposits. The frequency range of a conventional HEM system for mineral exploration, however, is relatively low and so not invariably suitable for its application to the fields of civil engineering because of its poor resolution in the shallower part of the earth. A DIGHEM HEM system was acquired by Nippon Engineering, with the frequencies chosen by the senior author. The five frequencies range from 220 Hz (the lowest) to 137,500 Hz (the highest). These frequencies improve the resolution of materials in the shallower part while maintaining a depth of investigation of greater than 100 m. This paper describes six case histories of geological and geotechnical surveys for civil engineering using HEM. These case histories include HEM surveys for investigating landslide, an alluvial area, root selection of road construction, areas related to dam and tunnel construction, and the simultaneous joint inversion of HEM and CSAMT data for a deep tunnel. These survey results show that HEM has sufficient resolution in both horizontal and vertical directins to contribute significantly to outlining the regional geology and its engineering problems.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.281-287
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• 2003

A Natural cavities were found at shallow depth during construction of a huge bridge in Moon-Kyung, Korea. The distribution patterns of cavities in the Moon-Kyung limestone were investigated carefully with a supplementary field job such as a structural geological survey, a geophysical survey, and a rock mechanical test in laboratory or field. A structural geological mapping produced a detail geological map on this area. It suggested that there were three faults in this area, and these faults had an influence on the mechanism of natural cavities. Among many kinds of geophysical surveys, an electrical resistivity prospecting was applied firstly on the specific area that was selected by results from the geological survey. Many evidences for cavities were disclosed from this geophysical data. Therefore, a seismic tomography was tested on the target area, which was focused by results from the electrical resistivity prospecting and was believed to have several large cavities. A distinct element numerical simulation using the UDEC was followed on the target area after completing all of field surveys. Data from field tests were directly dumped or extrapolated to numerical simulations as input data. It was verified from numerical analysis that several natural cavities underneath the foundation of the bridge should be reinforced. Based on the project result, finally, most of foundations for the bridge were re-examined and the cement grouting reinforcement was constructed on several foundations among them.

• Geophysics and Geophysical Exploration
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• v.10 no.1
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• pp.37-43
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• 2007

The MH21 Research Consortium has conducted a high-resolution 3D seismic survey and a seafloor geochemical survey, to explore methane hydrate reservoirs in the eastern Nankai Trough, offshore Japan. Excellent geological information about shallow formations was obtained from the high-resolution 3D seismic survey, which was designed to image the shallow formations where methane hydrates exist. The information is useful in constructing a geological and geochemical model, and especially to understand the complex geology of seafloor, including geochemical manifestations and the structure of migration conduits for methane gas or methane-bearing fluid. By comparing methane seep sites observed by submersibles with seismic sections, some significant relationships between methane hydrate reservoirs, free gas accumulations below the seafloor, and seafloor manifestations are recognised. Bathymetric charts and seafloor reflection amplitude maps, constructed from seismic reflections from the seafloor, are also useful in understanding the relationships over a vast area. A new geochemical seafloor survey targeted by these maps is required. The relationships between methane hydrate reservoirs and seafloor manifestations are becoming clearer from interpretation of high-resolution 3D seismic data. The MH21 Research Consortium will continue to conduct seafloor geochemical surveys based on the geological and geochemical model constructed from high-resolution 3D seismic data analysis. In this paper, we introduce a basis for exploration of methane hydrate reservoirs in Japan by fusion of 3D seismic exploration and seafloor geochemical surveys.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.10a
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• pp.67-70
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• 2009

송수신기 일체형인 소형 루프 시스템을 해저 전자탐사 기술의 적용 가능을 확인하는 과정의 시작 단계로 자기 쌍극자 송신원을 이용한 층서구조에서의 전자가 반응을 계산 하였다. 전도성인 해양 환경에서 측정되는 신호의 크기가 작은 한계가 있지만 전자기장 반응 해석을 통행 지하 하부의 정보를 얻을 수 있었다. 기반암 위의 층이 바닷물보다 저항성인 해저 지각인 경우와 전도성인 열수광상인 경우에 따라 반응이 달라짐을 확인하였고, 그 층의 두께에 따라서 변화하는 전자기 반응을 계산하여 탐지 가능한 층의 두께를 예상할 수 있었다. 송수신기가 모두 바다 속에 위치하기 때문에 송수신기의 배치 방법과 송수신기가 해저면에서 떨어지게 될 때 신호의 반응 변화를 파악하였다. 해양 소형 루프 전자탐사의 실제 적용을 위해서 이상의 연구들이 기초가 될 것으로 기대된다.

• Geophysics and Geophysical Exploration
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• v.23 no.3
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• pp.141-148
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• 2020

A drone platform built by Korea Institute of Geoscience and Mineral Resources (KIGAM) is introduced. The platform consists of various drone systems developed at KIGAM for photogrammetry, remote exploration, physical exploration, field operation methods, a vehicle-based drone control center, as well as a drone data platform for data storage, sharing, analysis, and visualization of the acquired data. The performance of the drone platform is verified using results obtained with the various systems, which are tested individually and in various combined applications. Finally, the possibility of using the KIGAM drone platform for geological surveys and mineral resource exploration is discussed.

• Geophysics and Geophysical Exploration
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• v.1 no.2
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• pp.92-100
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• 1998

Array CSAMT surveys were conducted in two areas where it was not easy to identify the presence of faults only with geological survey because of thick overburden. The purpose of these surveys were to locate the faults and to delineate the deep resistivity structures around the faults. The steep dip lineaments having high contrast in resistivity laterally and the low resistive zones having some width in the resistivity sections were interpreted as faults and fracture zones associated with faults, respectively, The good applicability of array CSAMT to the investigation of fault was recognized owing to the agreement between the interpretation results of array CSAMT and the conclusive evidences collected by the following geological survey. The evidences includes the recent exposure of fault and the trajectory of fault evidences of the survey line. A comparison of the applicabilities of array CSAMT method and the resistivity method using dipole-dipole array was presented with the results of both methods along a same traverse line.

• Geophysics and Geophysical Exploration
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• v.9 no.1
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• pp.121-128
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• 2006

Magnetic survey flights by helicopters are usually parallel to the topographic surface, with a nominal clearance, but especially in high-resolution surveys the altitudes at which observations are made may be too variable to be regarded as a smooth surface. We have developed a reduction procedure for such data using the method of equivalent sources, where surrounding sources are included to control edge effects, and data from points distributed randomly in three dimensions are directly modelled. Although the problem is generally underdetermined, the method of conjugate gradients can be used to find a minimum-norm solution. There is freedom to select the harmonic function that relates the magnetic anomaly with the source. When the upward continuation function operator is selected, the equivalent source is the magnetic anomaly itself. If we select as source a distribution of magnetic dipoles in the direction of the ambient magnetic field, we can easily derive reduction-to-pole anomalies by rotating the direction of the magnetic dipoles to vertical.