• 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.

• Geophysics and Geophysical Exploration
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• v.18 no.2
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• pp.39-53
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• 2015

Analysis of multi-channel seismic reflection profiles acquired from the southwestern margin of Ulleung Basin reveals that the cut and fill structures, which show U-shaped or V-shaped morphology, occur on variable size. The cut and fill structure mostly consists of fine-grained sediments on the well data and is characterized by transparent or semitransparent seismic facies on the seismic section. Such cut and fill structures dominantly occur in the syn-compressional megasequence (MSQ3), which was deposited during basin deformation of late Miocene, among the four megasequences of the study area. These cut and fill structures can be divided into three groups based on their size and formation time. The cut and fill structures of Group I were formed when Dolgorae structure was active, and occurred on a small scale. The cut and fill structures of group II were formed when both Dolgorae structure and Gorae V structure were active, and the number and size of those increased compared with group I. The cut and fill structures of group III were formed when Dolgorae structure was weaken gradually but Gorae V structure kept active, and the number and size of those decreased in comparison with group II. Consequently the cut and fill structures in the southwestern margin of Ulleung basin are interpreted as submarine canyon based on spatial distribution, size and fill sediment. They were controlled by the tectonic movement in response to basin closure and tectonic-induced sediment supply variation.

• Journal of the Korean earth science society
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• v.39 no.2
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• pp.154-163
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• 2018

Geoacoustic model comprises physical and acoustic properties of submarine bottom layers influencing sound transmission through sea water and underwater. This study suggested for the first time that we made a geoacoustic model of long-coring bottom layers at the SSDP-105 drilling site of the Ulsan coastal area, which is located in the southwestern inner shelf of the East Sea. The geoacoustic model of 52 m depth below seafloor with three-layer geoacoustic units was reconstructed in the coastal sedimentary strata at 79 m in water depth. The geoacoustic model was based on the data of a deep-drilled sediment core of SSDP-105 and sparker seismic profiles in the study area. For actual modeling, the geoacoustic property values of the models were compensated to in situ depth values below the sea floor using the Hamilton modeling method. We suggest that the geoacoustic model be used for geoacoustic and underwater acoustic experiments of mid- and low-frequency reflecting on the deep bottom layers in the Ulsan coastal area of the East Sea.

• 한국지구과학회:학술대회논문집
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• 2005.09a
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• pp.136-141
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• 2005

The K Ar ages, whole rock geochemistry and Sr Nd Pb isotopes have been determined for the submarine basalts dredged from the P2 and P3 segments of the Antarctic-Phoenix Ridge (APR), Drake Passage, Antarctica, for better understanding on temporal variation of magma chemistry in association with extinction of seafloor spreading. The fossilized APR is distant from the known hot spots, and consists of older N-MORB prior to extinction of spreading and younger E-MORB after extinction. The older N-MORB (3.5-6.4 Ma) occur in the southeast flank of the P3 segment (PR3) and the younger E-MORB (1.4-3.1 Ma) comprise a huge seamount at the P3 segment (SPR) and a big volcanic edifice at the P2 segment (PR2). The N-type PR3 basalts have higher Mg#, K/Ba, and CaO/Al2O3 and lower Zr/Y, Sr, and Na8.0 with slight enrichment in incompatible elements and almost flat REE patterns. The E-type SPR and PR2 basalts are highly enriched in incompatible elements and LREE. The extinction of spreading occurring at 3.3 Ma seems to have led to a temporal magma oversupply with E-MORB signatures. Geochemical signatures such as Ba/TiO2, Ba/La, and Sm/La suggest heterogeneity of upper mantle and formation of E-MORB by higher contribution of enriched materials to mantle melting, compared to N-MORB environment. E-MORB magmas beneath the APR seem to have been produced by low melting degree (up to 1% or more) at deeper low-temperature regime, where metasomatized veins consisting of pyroxenites have preferentially participated in the melting. The occurrence of E-MORB at the APR is a good example to better understand what kinds of magmatism would occur in association with extinction of spreading.

• Journal of the Korean Solar Energy Society
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• v.31 no.3
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• pp.29-35
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• 2011

This study draws economic expense factors according to the influence of generation resulted from slipstream and the arrangement of the complex when arranging and designing the complex for offshore windpower development as a model of 50MW offshore wind farm and conducts economics analysis. According to the result of the analysis, O (Optimize) arrangement was the one that has the highest generation for having the best windpower resources in terms of design and being least affected by slipstream; however, the arrangement requires expensive submarine cables and high installation cost. Therefore, according to the analysis of economics, it was thought that 50MW complex should have less economics as BC ratio 0.95 than the series arrangement of main wind direction and I+80 series arrangement would be rather more economical. This economics evaluation provides comparison according to the arrangement of the development complex considering the uncertainty of the electricity price and gross construction cost. And it is expected that the result of economics evaluation would greatly differ by installation capacity, and the reason is that the cost of electric infrastructure takes up a higher portion than the gross construction cost of the development complex. The only way to compensate this part is to make the windpower development complex larger. It seems that it will be necessary to enhance spot applicability to evaluate economics afterwards and pay consistent attention to and conduct follow-up research on the economics evaluation of the complex construction.

• Journal of Environmental Impact Assessment
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• v.11 no.1
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• pp.51-66
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• 2002

The purpose of this study is to analyze the geomorphological environment changes of tidal flat in the Cheonsu Bay. Especially, it centers on the changes in the sedimentary environment using remote sensing data. Multi-temporal Landsat data and topographic maps were used in this study. The results are summarized as follows: the tidal flat of Cheonsu Bay changes in many ways depending on the direction of the tidal current. In the neighborhood of Ganwoldo, the scale of the tidal flat has continuously been expanded due to the superiority of sedimentation after a tide embankment was built. When we analyzed the grain size of sediments and implemented in-situ field survey, it was found that the innermost part of the bay consists of a mud flat, with the midway part mixed flat, and the nearest part to the sea sand flat. On the other hand, in the neighborhood of Seomot isle and its beach, sedimentation is superior in the eastern part whereas erosion is superior in the western part. In other words, the western coast of the beach is contacted with the open seas and under much influence of ocean wave. The eastern coast is placed at the entrance of the bay and has sand bar and tidal flat developed due to submarine deposits that are accumulated on the sea floor by the tidal current. In conclusions, remote sensing methods can be effectively applied for quantitative analysis of geomorphological changes in tidal flat, and it is expected that the proposed schemes can be applied to another geomorphological environments such as beach, sand dune, and sand wave.

• Journal of the Korean Geophysical Society
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• v.4 no.1
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• pp.71-84
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• 2001

A study was initiated to investigate whether the groundwaters being discharged into the sea could be used as a possible water resources. This paper presents a preliminary information about the groundwaters being discharged along the shoreline of East Sea. Major discharge sites were selected primarily on the basis of the informaion on surface temperatures of the sea. Hydrogeologic and geographic conditions were also considered in selecting the major discharge sites. The development possibility of the discharging groundwater were estimated roughly, considering populations, industries and social development compatibilities of the selected areas. Groundwater dams and linked usage with surface water were suggested as possible development methods for the groundwaters.. Based on this study, we selected about 60 sites as the major discharge areas and tentatively recommended 6 sites as optimal sites for development of groundwaters being discharged into the sea. However, detailed in-situ hydrogeologic surveys are required prior to the final decision.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.9
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• pp.233-239
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• 2019

An unmanned underwater vehicle is a major weapon system that allows surveillance and reconnaissance missions in border areas or threatening areas where enemy submarines are present. Unmanned underwater vehicles can be used to explore underwater resources, predict disasters, and survey the topography of the ocean floor in the civilian fields, while in the defense fields, it can be used for anti-submarine reconnaissance and mine countermeasures. In this paper, we first investigate the main classification of unmanned underwater vehicles, and foreign R&D trends are analyzed based on the main classification criteria by weight, such as portable, light, heavy and large-scale unmanned underwater vehicles. Then we examine the trends in the development of domestic unmanned underwater vehicles. Finally, through the analysis of both domestic and foreign unmanned underwater vehicles, we present future development trends of unmanned underwater vehicles in order to set defense goals to counter the anticipated threats and diversified potential environment.

• Maritime Security
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• v.3 no.1
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• pp.115-140
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• 2021

The South China Sea is a significant maritime shipping route with abundant submarine and fishing resources. Over 40,000 ships pass through the South China Sea every year, constituting around 50% of global shipping and 66% of crude oil. In particular, 30% of Korea's import cargo and 90% of energy imports pass through this body of water. The US and China realized the significance of this sea area from early on and are embodying national interest through maritime security at the national strategic level by implementing the 'Indo-Pacific' and 'One Belt One Road' strategies, respectively. Such geopolitical conflicts are manifested in the 'freedom of navigation operations' by the US in the South China Sea. Despite its significance, there is a lack of studies in Korea on the freedom of navigation operations, and most previous studies only focus on analyzing international law and agreements. This article examines the origin and background of the strategic perception of the freedom of navigation operations and derives implications for the peace and security of the Korean Peninsula as the strategic competition between the US and China continues.

• 한국지구물리탐사학회:학술대회논문집
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• 2004.08a
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• pp.104-117
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• 2004

Dmitri Donskoi, which went down during the Russo-Japanese War occurred 100 years ago, was found by using geophysical exploration techniques at the 400 m water depth of submarine valley off Jeodong of Ulleung Island. In the submarine area with the rugged seabed topography and volcanic seamounts, in particular, the reliable seabed images were acquired by using the mid-to-shallow Multibeam exploration technique The strength of corrosion (causticity) of the sunken Donskoi, measured by the electrochemical method, decreased to 2/5 compared with the original strength.