• Fisheries and Aquatic Sciences
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• v.11 no.2
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• pp.103-112
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• 2008

Compressional sound velocities of shelf sediments in the South Sea of Korea, were measured in situ and in the laboratory for six cores. In situ sound velocity was measured using the Acoustic Lance (frequency of 7.5-15 kHz), while laboratory velocity was measured by the pulse transmission technique (frequency of 1MHz). Physical properties were relatively uniform with sediment depth, suggesting little effect of sediment compaction and/or consolidation. Average in situ velocity at each core site ranged from 1,457 to 1,488 m/s, which was less than the laboratory velocity of 1,503 and 1,604m/s. In muddy sediments the laboratory velocity was 39-47 m/s higher than in situ velocity. In sandy sediments, the difference was greater by an average of 116 m/s. Although the velocity data were corrected by the velocity ratio method based on bottom water temperature, the laboratory velocity was still higher than the in situ velocity (11-21 m/s in muddy sediments and 91 m/s in sandy sediments). This discrepancy may be caused by sediment disturbance during core collection and/or by the pressure of Acoustic Lance insertion, but it was most likely due to the frequency difference between in situ and laboratory measurement systems. Thus, when correcting laboratory velocity to in situ velocity, it is important to consider both temperature and frequency.

• 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.11 no.3
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• pp.167-176
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• 2008

Lau basin of the south Pacific, as an active back arc basin, is promising area bearing seafloor massive hydrothermal deposit that is located in a subduction zone between the Pacific ocean plate and Indo-Australian continental plate. We performed multi-beam bathymetry survey in the Lau basin using EM120, to find out high hydrothermal activity Bone. Fonualei Rift and Spreading Center (FRSC) and Mangatolou Triple Junction (MTJ) area were selected for precise site survey through seafloor morphology investigation. The result of surface and deep-tow magnetometer survey showed that Central Anomaly Magnetization High (CAMH) recorded which is associated with active ridge in FRSC-2 and revealed very low magnetic anomalies that can be connected to past or present high hydrothermal activity in MTJ-1 seamount area. Moreover, the physical and chemical tracers of hydrothermal vent flume, i.e., transmission, hydrogen ion concentration (pH), adenosine triphosphate (ATP), methane (CH4) by use of CTD system, showed significant anomalies in those areas. From positive vent flume results, we could conclude that these areas were or are experiencing very active volcanic activities. The acquired chimney and hydrothermal altered bed rock samples gave us confidence of the existence of massive hydrothermal deposit. Even though not to use visual exploration equipment such as ROV, DTSSS, etc., traditional marine geophysical investigation approach might be a truly cost-effective tool for exploring seafloor hydrothermal massive deposit.

• Geophysics and Geophysical Exploration
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• v.26 no.4
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• pp.229-237
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• 2023

The use of artificial sources such as explosives and mechanical vibrations for seismic exploration in urban areas poses challenges, as the vibrations and noise generated can lead to complaints. As an alternative to artificial sources, the surface waves generated by traffic noise can be used to investigate the subsurface properties of urban areas. However, traffic noise takes the form of plane waves moving continuously at a constant speed. To apply existing surface wave processing/inversion techniques to traffic noise, the recorded data need to be transformed into a virtual shot gather format using seismic interferometry. In this study, various seismic interferometry methods were applied to traffic noise data, and the optimal method was derived by comparing the results in the Radon and F-K domains. Additionally, the data acquired using various receiver arrays were processed using seismic interferometry, and the results were compared and analyzed to determine the most optimal receiver array direction for exploration.

• 한국지구물리탐사학회:학술대회논문집
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• 2004.06a
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• pp.170-175
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• 2004

• 한국지구물리탐사학회:학술대회논문집
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• 2010.10a
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• pp.75-78
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• 2010

• 한국석유지질학회:학술대회논문집
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• autumn
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• pp.29-37
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• 1999

Stratigraphic subdivision, correlation and depositional environments of Oligocene strata in the Cheju basin are studied using microfossils, wireline-log, trace elements from Geobuk-1, Okdom-1 and JDZ V-2 exploratory wells as well as seismic attributes. Application of these Integrated approaches is becoming increasingly an important tool in sedimentary and petroleum geology. The purpose of this study is to provide an integrated sequence-stratigraphic interpretation for petroleum system in the Cheju basin. During the last several years the Cheju basin has been studied for petroleum potential in terms of sequence stratigraphy. The strata assigned to be of the Early Miocene in the previous studies are reinterpreted to be of Oligocene in age. Depositional environments of these strata are also reinterpreted to have been influenced significantly by marine floodings. This interpretation is supported by the lines of evidence such as occurrences of abundant dinoflagellates and calcareous nannofossils, higher sulfur (1000-10000 ppm), TOC contents $(>1{\~}3{\%})$ and hydrogen index, and specific biomarkers such as dinostrane and $C_{30}$ 4-methyl steranes. Seismic facies, determined as a fairly continuous amplitude reflection, relatively parallel uniform strata, also provides a clue for recognizing marine transgressions during the Oligocene. Two 2nd--order stratigraphic cycles are observed in Oligocene strata based on well-log responses and the presence of microfossils. Each sequence comprises shallow marine deposits in the lower part and inner-outer neritic deposits in the upper part, thus showing a upward-deepening trend. In petroleum exploration point of view, the presence of marine strata would provide a better exploration potential for source rock and reservoir quality in the Cheju basin, offshore Korea.

• Journal of the Korean Geophysical Society
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• v.6 no.1
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• pp.31-38
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• 2003

Multi-channel seismic survey, which has been mainly employed in oil prospecting, is carried out as a high resolution shallow marine seismic exploration. Fault drop as small as 1 m can be resolved by employing high-resolution seismic survey. Similar to the effect of shallow inhomogenities in the land seismic data, due to occurrence of swell quite often higher than 1 m, shallow marine seismic data tend to be severely degraded. Suppression of such a swell effect is critical in processing of steps of marine seismic shallow high-resolution data. Compared to the moving average depth method, a newly developed method using cross-correlation technique is found out to be very effective in increasing the resolution of the shallow reflection events by accuratly elucidating the depth of sea bottom.

• Ocean Systems Engineering
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• v.8 no.1
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• pp.21-32
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• 2018

Due to the escalation in hydrocarbon consumption, the offshore industry is now looking for advanced technology to be employed for deep sea exploration. Riser system is an integral part of floating structure used for such oil and gas extraction from deep water offering a system of drill twines and production tubing to spread the exploration well towards the ocean bed. Thus, the marine risers need to be precisely employed. The incorporation of the strengthening material, fiber reinforced polymer (FRP) for deep and ultra-deep water riser has drawn extensive curiosity in offshore engineering as it might offer potential weight savings and improved durability. The design for FRP strengthening involves the local design for critical loads along with the global analysis under all possible nonlinearities and imposed loadings such as platform motion, gravity, buoyancy, wave force, hydrostatic pressure, current etc. for computing and evaluating critical situations. Finite element package, ABAQUS/AQUA is the competent tool to analyze the static and dynamic responses under the offshore hydrodynamic loads. The necessities in design and operating conditions are studied. The study includes describing the methodology, procedure of analysis and the local design of composite riser. The responses and fatigue damage characteristics of the risers are explored for the effects of FRP strengthening. A detail assessment on the technical expansion of strengthening riser has been outlined comprising the inquiry on its behavior. The enquiry exemplifies the strengthening of riser as very potential idea and suitable in marine structures to explore oil and gas in deep sea.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.10a
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• pp.128-128
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• 2009