• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.25 no.4
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• pp.117-131
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• 2020

Although most species in genus Zostera inhabit shallow coastal areas and bays with weak wave energy, the Asian eelgrass, Zostera asiatica is distributed in deep water depth (8-15 m) unlike other seagrasses on the eastern coast of Korea. To examine factors limiting distribution Z. asiatica in relatively deep coastal areas, a transplantation experiment was conducted on October 2011, in which Z. asiatica shoots were transplanted from the reference site (donor meadow, ~9 m) to the shallow transplant site (~3 m). We compared shoot density, morphology, and productivity of Z. asiatica as well as environmental factors (underwater irradiance, water temperature, and nutrients) between the reference and transplant sites from October 2011 to September 2012. Shoot density and shoot height of transplants dramatically decreased within a few months after transplantation, but were similar with Z. asiatica in the reference site during spring. Shoot productivity were significantly higher in the transplant site than in reference site because of high light availability and nutrient concentrations. Transplants showed photoacclimatory responses such as higher rETR_max and E_k and lower photosynthetic efficiency in the transplant site than those in the reference site. Most of Z. asiatica transplant in the shallow transplant site disappeared in summer, which may be due to the high wave energy and physical damages induced by typhoons (TEMBIN and SANBA) in August and September 2012. According to the results of this study, Z. asiatica could not survive in shallow areas despite of more favorable light and nutrient conditions. Thus, Z. asiatica may restrictively occur in deep areas to avoid the intense physical stresses in the shallow area on the east coast of Korea.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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• v.25 no.1
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• pp.57-81
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• 1997

Numerical prediction of nocturnal thermal high in summer of the 1995 near Taegu city located in a basin has been carried out by a non-hydrostatic numerical model over complex terrain through one-way double nesting technique in the Z following coordinate system. Under the prevailing westerly winds, vertical turbulent fluxes of momentum and heat over mountains for daytime hours are quite strong with a large magnitude of more than $120W/\textrm{m}^2$, but a small one of $5W/\textrm{m}^2$ at the surface of the basin. Convective boundary layer (CBL) is developed with a thickness of about 600m over the ground in the lee side of Mt. Hyungje, and extends to the edge of inland at the interface of land sea in the east. Sensible heat flux near the surface of the top of the mountain is $50W/\textrm{m}^2$, but its flux in the basin is almost zero. Convergence of sensible heat flux occurs from the ground surface toward the atmosphere in the lower layer, causing the layer over the mountain to be warmed up, but no convergance of the flux over the basin results from the significant mixing of air within the CBL. As horizontal transport of sensible heat flux from the top of the mountain toward over the basin results in the continuous accumulation of heat with time, enhancing air temperature at the surface of the basin, especially Taegu city to be higher than $39.3^{\circ}C$. Since latent heat fluxes are $270W/\textrm{m}^2$ near the top of the mountain and $300W/\textrm{m}^2$ along the slope of the mountain and the basin, evaporation of water vapor from the surface of the basin is much higher than one from the mountain and then, horizontal transport of latent heat flux is from the basin toward the mountain, showing relative humidity of 65 to 75% over the mountain to be much greater than 50% to 55% in the basin. At night, sensible heat fluxes have negative values of $-120W/\textrm{m}^2$ along the slope near the top of the mountain and $-50W/\textrm{m}^2$ at the surface of the basin, which indicate gain of heat from the lower atmosphere. Nighttime radiative cooling produces a shallow nocturnal surface inversion layer with a thickness of about 100m, which is much lower than common surface inversion layer, and lifts extremely heated air masses for daytime hours, namely, a warm pool of $34^{\circ}C$ to be isolated over the ground surface in the basin. As heat transfer from the warm pool in the lower atmosphere toward the ground of the basin occurs, the air near the surface of the basin does not much cool down, resulting in the persistence of high temperature at night, called nocturnal thermal high or tropical night. High relative humidity of 75% is found at the surface of the basin under the moderate wind, while slightly low relative humidity of 60% is along the eastern slope of the high mountain, due to adiabatic heating by the srong downslope wind. Air temperature near the surface of the basin with high moisture in the evening does not get lower than that during the day and the high temperature produces nocturnal warming situation.

• Korean Journal of Ichthyology
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• v.19 no.4
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• pp.378-386
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• 2007

To study the composition of the developmental stages of Maurolicus japonicus eggs distributed in the western Korea Strait, we investigated the water temperature, salinity, eggs and larvae in December 2002. The Korea Strait Bottom Cold Water (KSBCW) lower than $10^{\circ}C$ was found in off the Ulsan and Busan where M. japonicus eggs were the most abundant. The composition of the developmental stages of M. japonicus eggs at each station were composed of 37.7~89.5% in the first stage, 8.5~37.8% in the middle stage and 0.0~24.7% in the last stage respectively. In the southern area where the KSBCW appeared, the first stage eggs occupied 73.3~89.5%. The high percentage of the first stage eggs indicated that the eggs should be transported by the cold water lower than $10^{\circ}C$ from the Ulleung Basin in the East Sea. In the northern area where the KSBCW was not found, the first, middle and last stage eggs were composed of 37.5%, 37.8% and 24.7% respectively. The ratios of middle and last stage eggs were much higher than those in the southern area with the KSBCW, which implies that the eggs are recruited into the northern area from the southern area with the KSBCW by the Tsushima Warm Current. The pre-larvae found only in the middle and northern part of the study area would be hatched during the transport of eggs from the southern area with the KSBCW by the Tsushima Warm Current.

• The Journal of the Korea Contents Association
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• v.21 no.6
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• pp.435-444
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• 2021

This paper discusses the geometrical interpretation of the Taegeuk Shapes of Kameun Temple through the geometric analysis of mathematics. Based on the literature, This paper attempted to clarify that the origin of Gameunsa's founding of the spirit of patriotism may coincide with historical records through historical literature and geometric meaning. First, the background of the founding of Kameun temple, geographical location located near the East Sea, especially the history of the ancient Chinese mathematics at the time, And that mathematical knowledge influenced all fields such as agriculture, architecture, and art. Secondly, it is related to the historical record as the space of about 60 centimeters, which is uniquely underground, was identified as the structure of the excavated space. It is thought that there is a strong correlation with the origin that the King Munmu changed into a dragon, and set up the temple to be able to stay. Based on these, the clues of the interpretation of the taegeuk and the triangular pattern were searched in the samcheon yanggi(參天兩地) of the Oriental and circumference of the Western. The taegeuk and triangular patterns represent the symbols of yin-yang harmony, which correspond to the origin of its creation. the Korean people regarded the mysterious dragon as a symbol of yinyang harmony. In conclusion the Shapes of Kameun temple's stone is consistent with the contents mentioned in the historical record.

• 한국해양학회지
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• v.25 no.2
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• pp.74-83
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• 1990

The similarity in Mesozoic geology between the Antarctic Peninsula and South America indicates the possibility that they had situated along the same tectonics line before the separation of southwestern Gondwanaland. The igneous activity around the Antarctic Peninsula, including the South Shetland islands, can be correlated with the South American Cordillera Orogeny due to the subduction of Farallon/Phoenix plate until late Mesozoic. However igneous activity in Tertiary correlates with the tectonics movement accompanying the formations of Drake passage and Scotian sea. The south Shetland islands form a Jurassic-Quaternary miasmatic island arc on the sialic basement of schist and deformed sedimentary rocks. Forming of the South Shetland Islands arc began during the latest Jurassic or earliest Cretaceous from the southwestern part of the archipelago. The igneous activity migrated northeasterly and continued in most areas until late Tertiary. The entire arc-forming period, between late Jurassic and late tertiary times, was characterized by emplacement and eruption of magmas of intermediate between island-arc tholeiite and calc-alkaline types. However, Quaternary volcanic rocks show strong alkaline affinities which corresponds to the switch from compressional to intra: plate tensional tectonics. The rocks of late Cretaceous to Tertiary, mainly found in King George Island, consist of lava of basalt to andesite and intercalated pyroclastic rocks. Some of the volcanic rocks, which ofter called quartz-pyrite lodes'are severely altered and include much content of calcite,silica and pyrite.The stratographic succession of King George Island can be divided into two formation:Fields formation and Hennequin formation.The Fildes formation crops out at the west side of Admiralty Bay n King George Island,while the Hennequin formation at the east side of the bay.These two formtions are thought to be formed contempiranceously.The Fildes formation consists of altered olivine-basalt and basaltic andestie, whereas the Hennequin formation consists of fine-grained hypersthene-augite-andesite.Both formations interclate pyroclastic rocks.

• The Korean Journal of Malacology
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• v.29 no.2
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• pp.147-154
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• 2013

In Incheon bay, mass mortalities of Manila clam associated with winter storms have been reported. In the present study we have monitored pathologic condition of the clams stranded on the tidal flats by the winter storms occurred in late March to early April in 2007. The field surveyed indicated that mortality of the Manila clam in the study areas ranged 10-15%. Condition index, a ratio of tissue weight to the shell weight, of the stranded clams was significantly lower than the non-stranded normal clams collected from the same locations (p < 0.05), indicating that the stranded clams were comparatively in poor physiological condition. Perkinsus olseni, the protozoan parasite was observed most of clams used in the analysis and the infection prevalence ranged 77-90%. The infection intensity of P. olseni determined using Ray's fluid thioglycollate medium (RFTM) cultivation and the 2M NaOH digestion assay indicated that the clams collected during late March and early April in 2007 involved 67,182-1,124,727 P. olseni cells/g tissue. The infection intensity of clams from Gung-Pyeung was significantly higher than the intensities observed from Dae-Bu and Young-Heung (p < 0.05). No clear correlation was found between the infection intensities of P. olseni in the non-stranded normal clams and the stranded clams. The stranded Manila clams were also infected with trematode parasite with the prevalence ranged 5 (Young-Heung) to 12.5% (Dae-Bu). The trematode-infected clams exhibited castrated follicles in the gonad, a typical sign of trematode infection. It was believed that mass mortality of Manila clam observed in this study was associated with the poor physiological condition as indicated by CI, although impacts of the parasite infection cannot be ruled out.

• The Journal of Engineering Geology
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• v.29 no.1
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• pp.1-12
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• 2019

Earthquake can change underground stress condition around the hypocenter and affect the fracture systems of the rocks. In Korea, the M5.8 Gyeongju earthquake on September 12, 2016 and M5.4 Pohang earthquake on November 15, 2017 occurred inside the Yangsan fault zone and possibly affected the fracture systems in the Yangsan fault zone and nearby rock masses. In this study, the characteristics of the fracture system (fracture orientation, number of the fractures, fracture spacing and aperture, dip angle, fracture density along depth, and relative rock strength) of the rocks in the low/intermediate level radioactive waste repository site located in the coastal area of the East Sea are analyzed by the impact of the Gyeongju and Pohang earthquakes using acoustic televiewer data taken from the boreholes at the radioactive waste repository site in 2005 and 2018. As a result of acoustic televiewer logging analysis, the fracture numbers, fracture aperture, and fracture density along depth overall increased in 2018 comparing to those in 2005. This increase tendency may be due to changes in the fracture system due to the impact of the earthquakes, or due to weathering of the wall of the boreholes for a long period longer than 10 years after the installation of the boreholes in 2005. In the borehole KB-14, on the whole, the orientation of the fractures and the average fracture spacing are slightly different between 2005 and 2018, while dip angle and relative rock strength in 2005 and 2018 are similar each other.

• Geophysics and Geophysical Exploration
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• v.12 no.3
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• pp.255-262
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• 2009

Conventionally, vertical-seismic-profiling (VSP) survey that provides high-resolution information has mainly performed to obtain the exact depth of the gas hydrate-bearing sediment, which is one of the key factors in the development of the gas hydrate. In this study, we extracted interval velocities and created corridor stacks from the first domestic zero-offset VSP data, which were acquired with three component receivers at UBGH09 borehole in Ulleung Basin where gas hydrate exists. Then we compared the corridor stacks with a CMP stacked section from surface seismic data. First of all, we converted the signals recorded with three component receivers to true vertical and horizontal components by phase rotation, and divided the data into direct waves and reflected waves by wavefield separation processing. The trend of the interval velocity extracted from the zero-offset VSP was similar to that of the sonic log obtained at the same borehole. Because the interval velocity of the gas hydrate-bearing sediment above the BSR was high, and it decreased suddenly through the BSR, we could infer that free gas is accumulated below the BSR. The results of comparing the corridor stacks to the CMP stacked section of the surface seismic data showed that most reflection events agreed well with those in the surface CMP stacked section and that the phase-rotated VSP data corresponded better with the surface seismic data than the VSP data without phase rotation. In addition, by comparing a corridor stack produced from the transverse component with the CMP stacked section of the surface seismic data, we could identify PS mode-converted reflections in the CMP stacked section.

• 한국해양학회지
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• v.30 no.6
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• pp.565-583
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• 1995

We have used a nonlinear quasi-geostrophic model to study effects of lateral friction and bottom topography on the motion of warm eddies. The two empirical orthogonal functions of the stream function, accounting for the vertical structure, represent the barotropic and first baroclinic dynamic modes. This model is integrated 360 days on a 1000 km ${\times}$ 1000 km domain with a resolution of 10 km ${\times}$ 10 km including both the thermocline and idealized topography of the East Sea. Prescribed inflow through the Korea Strait is compensated by outflow through the Tsugaru Strait. The balance between the nonlinear advection term and the planetary ${\beta}$-effect tends to make northward movement of warm eddy over a flat bottom. The motion of a warm eddy over a sloping topography can be dominated by the nonlinear advection, while nonlinearity plays a secondary role over a flat topography. For eddies dispersing over topography, the nonlinear tendency is a function of time. For a strong warm eddy, northward propagation can occur. For intermediate strength of eddies one might expect a balance between the nonlinear term and the topographic ${\beta}$-effect. As nonlinearity decreases with eddy dispersion, southward motion along the slope may occur by such as a topographic Rossby wave. Our numerical simulations have confirmed the importance of lateral friction on eddy motions, in such a way that the northward penetration of the warm eddy increases drastically by the decrease of the lateral friction. The northward motion of warm eddy can be prevented by reducing the Reynolds number sufficiently. We have also demonstrated the crucial role of topographic effects in the eddy motion process.

• The Journal of the Petrological Society of Korea
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• v.18 no.2
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• pp.137-151
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• 2009

Synthetic analyses of field data, including rock facies, contact relationships, petrography, structural elements, and etc., and previous geochemical and absolute age data of the Tertiary Churyeong Breccia and its surrounding volcanics in the Gyeongju city, Korea, have led to the following results. (1) The Tertiary rocks are divided into the dacitic tuffs, Churyeong Breccia, and andesitic rocks in ascending order. The dacitic tuffs are unconformably overlain by the Churyeong Breccia which is intruded by or conformably overlain by the andesitic rocks. (2) The dacitic tuffs are correlated with the Paleocene${\sim}$Eocene Wangsan dacitic volcanics, while the Churyeong Breccia and andesitic rocks are correlated with the early Early Miocene Andongri Formation and Yongdongri Tuffs in the Waeup Basin, respectively. (3) The Churyeong Breccia accumulated rapidly in the NE-trending graben about 1.5 km in width during the crustal extension in the NW-SE direction due to the East Sea opening. (4) Dacitic${\sim}$andesitic volcanism and crustal extension were active during the early Early Miocene times in SE Korean peninsula. During the deposition the Churyeong Breccia, especially, the volcanism ceased for some time, but the active normal faulting led to the formation of grabens in places.