• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.210-221
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• 1998

In the period from the year 1500 to 1980. at least 14 large earthquake with epicenters in the northeastern China and Yellow Sea were felt or destructive in the Korean Peninsula. The most sigmificant events among them were the 1668 July 25 Tancheng earthquake of mamnitude 8.5, and the 1975 Feb. 4 Haicheng earthquake of magnitude 7.3. The Haicheng earthquake of the year 1975 in am extraordinary one among those occurred in the northeastern China in the 20th century in the sense the Shake of the event affected all over the Korean Peninsula. The tremor was felt even at the southeastern tip of the Korea and northern part of Kyushu 700km far away from the epicenter. In order to see the variation and trend of the effect of the Haicheng earthquake on the Korean Peninsula, the two data sets of the northern and southern parts of the peninsula were merged into one combined data set. The spatial variation of intensity shows smooth decrease from the value 4 of the northwestern region near the source to the value 1 of the Cheju Island and Kjushu. However, there are four regions of locally high intensity value. They are the region along downstream of Abrok(Yalu) River with intensity 5, the region around Shinpo of intensity 4, the area comprising Seoul and Chuncheon Cities of intensity 4, and Pohang-Pusan area of intensity 3. We suppose that there might be three types of possible mechanisms. The first one is concerned with the lateral inhomogeneity of velocity in the crust caused by wide distribution of relatively fractured rock. The second one is related with reflections of surface waves caused by the crestal thinning effect at border regions of the Peninsular in contact with the Ulleung Basin and the Japan Basin. The third possibility is local site effect caused by thick Tertiary or Quaternary rocks and soil layers.

• Journal of Ocean Engineering and Technology
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• v.31 no.4
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• pp.274-280
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• 2017

Generally, global performance analysis in offshore platforms is performed using potential-based numerical tools, which neglect hydrodynamic viscous effects. In comparison with the potential theory, computational fluid dynamics (CFD) methods can take into account the viscous effects by solving the Navier-Stokes equation using the finite-volume method. The open-source field operation and manipulation (OpenFOAM) C++ libraries are employed for a finite volume method (FVM) numerical analysis. In this study, in order to apply CFD to the global performance analysis of a hull-mooring coupled system, we developed a numerical wave basin to analyze the global performance problem of a floating body with a catenary mooring system under regular wave conditions. The mooring system was modeled using a catenary equation and solved in a quasi-static condition, which excluded the dynamics of the mooring lines such as the inertia and drag effects. To demonstrate the capability of the numerical basin, the global performance of a barge with four mooring lines was simulated under regular wave conditions. The simulation results were compared to the analysis results from a commercial mooring analysis program, Orcaflex. The comparison included the motion of the barge, catenary shape, and tension in the mooring lines. The study found good agreement between the results from the developed CFD-based numerical calculation and commercial software.

• Journal of Korean Society on Water Environment
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• v.39 no.4
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• pp.316-328
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• 2023

In this study, the characteristics of nonpoint pollutant outflow and contribution rate of pollution in Songya-stream mainstream and tributaries were analyzed. Further, water pollution management and improvement measures for pollution-oriented rivers were proposed. An on-site investigation was conducted to determine the inflow of major pollutants into the basin, and it was found that pollutants generated from agricultural land and livestock facilities flowed into the river, resulting in a high concentration of turbid water. Based on the analysis results of the pollution load data calculated through actual measurement monitoring (flow and water quality) and the occurrence and emission load data calculated using the national pollution source survey data, the S3 and S6 were selected as the concerned pollution tributaries in the Songya-stream basin. Results of cluster analysis using Pearson correlation coefficient evaluation and Density based spatial clustering of applications with noise (DBSCAN) technique showed that the S3 and S6 were most consistent with the C2 cluster (a cluster of Songya-stream mainstream owned area) corresponding to the mainstream of Songya-stream. The analysis results of the major pollutants in the concerned pollution tributaries showed that livestock and land pollutants were the major pollutants. Consequently, optimal management techniques such as fertilizer management, water gate management in paddy, vegetated filter strip and livestock manure public treatment were proposed to reduce livestock and land pollutants.

• Economic and Environmental Geology
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• v.44 no.1
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• pp.83-94
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• 2011

Extra heavy oil reservoirs are distributed over the world but most of them is deposited in the northern part of the Orinoco River in Venezuela, in the area of 5,500 $km^2$, This region, which has been commonly called "the Orinoco Oil Belt", contains estimated 1.3 trillion barrels of original oil-in-place and 250 billion barrels of established reserves. The Venezuela extra heavy oil has an API gravity of less than 10 degree and in situ viscosity of 5,000 cP at reservoir condition. Although the presence of extra heavy oil in the Orinoco Oil Belt has been initially reported in the 1930's, the commercial development using in situ cold production started in the 1990's. The Orinoco heavy oil deposits are clustered into 4 development areas, Boyaco, Junin, Ayachoco, and Carabobo respectively, and they are subdivided into totally 31 production blocks. Nowadays, PDVSA (Petr$\'{o}$leos de Venzuela, S.A.) makes a development of each production block with the international oil companies from more than 20 countries forming a international joint-venture company. The Eastern Venezuela Basin, the Orinoco Oil Belt is included in, is one of the major oil-bearing sedimentary basins in Venezuela and is first formed as a passive margin basin by the Jurassic tectonic plate motion. The major source rock of heavy oil is the late Cretaceous calcareous shale in the central Eastern Venezuela Basin. Hydrocarbon materials migrated an average of 150 km up dip to the southern margin of the basin. During the migration, lighter fractions in the hydrocarbon were removed by biodegradation and the oil changed into heavy and/or extra heavy oil. Miocene Oficina Formation, the main extra heavy oil reservoir, is the unconsolidated sand and shale alternation formed in fluvial-estuarine environment and also has irregularly a large number of the Cenozoic faults induced by basin subsidence and tectonics. Because Oficina Formation has not only complex lithology distribution but also irregular geology structure, geological evolution and characteristics of the reservoirs have to be determined for economical production well design and effective oil recovery. This study introduces geological formation and evolution of the Venezuela extra heavy oil reservoirs and suggest their significant geological characteristics which are (1) thickness and geometry of reservoir pay sands, (2) continuity and thickness of mud beds, (3) geometry of faults, (4) depth and geothermal character of reservoir, (5) in-situ stress field of reservoir, and (6) chemical composition of extra heavy oil. Newly developed exploration techniques, such as 3-D seismic survey and LWD (logging while drilling), can be expected as powerful methods to recognize the geological reservoir characteristics in the Orinoco Oil Belt.

• The Korean Journal of Petroleum Geology
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• v.5 no.1_2 s.6
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• pp.1-8
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• 1997

Seismic stratigraphic analysis of the high resolution profiles obtained from the southeastern shelf of Korea divided the deposits into 4 sequences; 1) sequence D, 2) sequence C, 3) sequence B and 4) sequence A (Holocene sediments). Sequence D was deposited in shallow-water environment at west of the Yangsan Fault as the basin subsided. On the other hand, the eastern part was formed at the slope front. Landward part of the slope-front fill sediments were eroded and redeposited nearby slope due to the syndepositional tilting of the basin. This tilting probably resulted from the continuous closing of the Ulleung Basin. Sequence C is made of stacked successions of the lowstand fluvial sediments, transgressive sediments and marine highstand sediments derived from the paleo-river in the western part of the Yangsan Fault. Sequence C in the eastern part of the Yanshan Fault was formed at the shelf break. Progradation of the lowstand sediments resulted in broadening of the shelf. Sequence C in the eastern part was also tilted but the tilting was weaker than in Sequence D. During the formation of sequence B the tilting stopped and the point source instead of the line source started in both sides of the Yangsan Fault. Sequence B was composed of the highstand systems tract partially preserved around the Yokji island, lowstand systems tract mainly preserved in the Korea Trough and transgressive systems tract. After the stop of the tilting, the force of compression due to the closing of the Ulleung Basin may be released by the strike-slip faults instead of tilting.

• The Korean Journal of Petroleum Geology
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• v.11 no.1 s.12
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• pp.1-8
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• 2005

Seventeen exploratory wells have been drilled in the Block VI-1 of offshore Korea, which is located in the southern part or the Ulleung Basin. Gas show has been recognized from most of the wells, and gas and condensate have been accompanied in some wells. Commercial discovery of gas, accompanied by condensate, has been made from Gorae V well. The reservoir gases or the Dolgorae III, Gorae I, and Gorae V wells in the Ulleung Basin mainly consists of hydrocarbon gases (>93%). These gases are thermogenic wet gases which contain more than 96% of the methane and result from the cracking of petroleum or kerogen. Based on the chemistry and composition of the gases and stable isotope data, they seem to be generated from different source rocks. The condensates from the Gorae I and V wells are mostly generated from terrestrial organic matter. Lacustrine organic matter may not play an important role for the generation of these condensates. The condensates from the Gorae V wells consist predominantly of terrestrial organic matter but with minor subsidiary input from marine organic matter. The condensates from Gorse I and V wells may be generated from different source rocks. The thermal maturity level of the condensates from the Gorae V well ranges from early to middle oil generation zone and condensate from Gorae I reaches middle oil window. Correlation or the thermal maturation level of the condensates and organic matter in the sediments reveals that a depth of the generation of liquid hydrocarbons can be inferred to 3,000 m and 3,900 m for the Gorae V and I wells, respectively. Gorae V well, however, did not reach the target depth and the geochemical data of the Gorae I well were obscured due to the severe sediment caving in.

• Journal of Environmental Impact Assessment
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• v.27 no.4
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• pp.353-366
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• 2018

The purpose of this study was assessment the quality of water by using the statistical analysis technique of the Water flow and water quality from January 2012 to December 2016 at the unit basin for total pollutant load management system (TPLMS) in the Imjin River. Water flow and water quality were monitored at an average of 8 day intervals, 11 parameters were used for correlation analysis, principal component analysis (PCA), factor analysis (FA), and cluster analysis (CA). The Hierarchical CA was classified into three according to the change of space, such as natural rivers, urban rivers, point with large influence of point pollution source, it was found that the type of contamination source the similarity of water quality affected the classification of cluster. Using one-way analysis of variance (ANOVA) and post-hoc Analysis, there were statistically significant differences between mean values among the clusters. Correlation analysis showed the correlation coefficient between $COD_{Mn}$ and TOC was 0.951 (p<0.01) and the correlation was statistically significantly higher. According to the result PCA and FA, 3 principal components can explaining 72% of the total variations in water quality characteristics and main factor was EC, $BOD_5$, $COD_{Mn}$, TN, TP and TOC indirect indicators of organic matter and nutrients were influenced. This study presented the regression equation obtained by applying the factor scores to the multiple linear regression analysis and concluded that the management Indirect indicators of organic matter and nutrients is important for water quality management in the Imjin River basin.

• The Journal of the Petrological Society of Korea
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• v.25 no.1
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• pp.51-67
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• 2016

Geochemical characteristics of the Early Cretaceous igneous rocks from eastern China and the Gyeongsang Basin, Korean Peninsula has been summarized. They have wide range of lithological variation with extrusive picrite-basalt-andesite-trachyte-rhyolite and lamprophyre, and intrusive gabbro-diorite-monzonite-syenite-granite and diabase in eastern China, mostly belonging to the high-K calc-alkaline or shoshonitic series. The volcanic rocks intercalated with the Hayang Group sedimentary assemblages in the Gyeongsang basin are high-K to shoshonitic basaltic trachyandesites. The Early Cretaceous basaltic rocks studied mostly fall within the field of within-plate basalts on the Zr/Y-Zr and Nb-Zr-Y tectonic discrimination diagrams. On a Sr-Nd isotope correlation diagram, basaltic rocks from the North China block (NCB) and the continent-continent collision zone (CZ) between the North and South China blocks plot into the enriched lower right quadrant along the extension of the mantle array. The initial $^{87}Sr/^{86}Sr$ ratios of basaltic rocks from the South China block (SCB) are indistinguishable from those of the NCB and CZ basaltic rocks, but their ${\varepsilon}_{Nd}$ (t) values are relatively more elevated, plotting in right side of the mantle array. Basaltic rocks from the NCB and CZ are characterized by low $^{206}Pb/^{204}Pb(t)$ ratios, lying to the left of the Geochron on the $^{207}Pb/^{204}Pb(t)$ vs. $^{206}Pb/^{204}Pb(t)$ correlation. Meanwhile, the SCB basaltic rocks have relatively radiogenic Pb isotopic compositions compared with those of the NCB and CZ basaltic rocks. Basaltic rocks from the Hayang Group plot within the field of the NCB basaltic rocks in Sr-Nd and Pb-Pb isotope spaces. Metasomatically enriched subcontinental lithospheric mantle (SCLM) is likely to have been the dominant source for the early Cretaceous magmatism. Asthenospheric upwelling under an early Cretaceous extensional tectonic setting in eastern China and the Korean Peninsula might be a heat source for melting of the enriched SCLM. Metasomatic agents proposed include partial melts of lower continental crust delaminated and foundered into the mantle or subducted Yangtze continental crust, or fluid/melt derived from the subducted paleo-Pacific plate.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.4
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• pp.345-356
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• 2011

Based on the consideration of land based pollutant discharges from the basin and seawater quality related carrying capacity and the seawater quality improvement in receiving water bodies of Yeoja Bay where eutrophication and organic pollution are in progress, were evaluated. The permissible inflow loads of BOD, TN and TP by using the geographical features and box modelling method were estimated. As results, it is shown that the reduction rate of discharged BOD and TP loads were 39.3% and 30.8 %, respectively, however, 6.9% was estimated for TN. According to the pollutant loading in each tributary and generated load of the basin, it is given much weight on the land use group, and also was shown in discharged load estimation. This suggests that it is important to control nonpoint source pollutant such as livestock and land use groups as well as point source to contribute the proposition of the water quality improvement plan according to the characteristics of the bay.

• Journal of Wetlands Research
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• v.18 no.3
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• pp.232-243
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• 2016

In order to establish the watershed water quality management strategy of Total Maximum Daily Load(TMDL), it is necessary to understand the relationship between water quality component impacts, and to identify the impacts on downstream target point of watershed water quality management of waste treatment plant(WTP) discharge and upstream/tributary loads. In this study, we determined the impacts between the water quality contaminants, and traced water pollution sources using monitoring data of ministry of environment in tributaries and main stream and WTP monitoring data. Test area is set to Geumho river basin which has characteristics of urban and rural area and composes of GeumhoA, GeumhoB, GeumhoC watershed units in TMDL. The clustering with five grades of discharge data and the correlation analysis were performed through the FDC(Flow duration curve) analysis, which more clearly identified the points and water contaminants deteriorating target water quality of downstream point. This can be used as a tool for tracing pollutants with FDC analysis, and will help us establish the watershed water quality management strategy for TMDL target point in watershed more effectively.