• Animal Systematics, Evolution and Diversity
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• v.37 no.4
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• pp.273-279
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• 2021

Branchinotogluma segonzaci (Miura and Desbruyères, 1995) occurs in hydrothermal vent fields of the southwestern Pacific Ocean. We morphologically compared B. segonzaci from the North Fiji Basin with the original description from the Lau Basin and a subsequent study of specimens from the Manus Basin. The main characteristics of all B. segonzaci populations were similar having 21 segments, 10 pairs of elytra, cylindrical-shaped anterior lobes, and ventral papillae on segment 12 and ventral lamellae on segments 13-17 in males. However, the specimens from the North Fiji Basin had rounded to sub-renifrom elytra rather than oval in the original description. Additionally, we newly obtained 11 cytochrome oxidase subunit I (COI) DNA barcodes from the North Fiji Basin and Tonga Arc populations and compared them with known COI DNA barcodes of Branchinotogluma species. Thirteen sequences of B. segonzaci showed 0.0-1.07% intraspecific variation and formed two clades in the COI neighbor-joining tree, whereas the interspecific variation among Branchinotogluma species was 8.19-22.4%. The results of this study contribute to biogeographic studies of B. segonzaci and the evolution of polynoid scale worms in chemosynthesis-based ecosystems.

• Journal of the Korean Geophysical Society
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• v.9 no.3
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• pp.189-197
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• 2006

The Korea Plateau is a continental fragment rifted and partially segmented from the Korean Peninsulaat the initial stage of the opening of the East Sea (Japan Sea). We interpreted marine seismic profiles from the South Korea Plateau in conjunction with swath bathymetric to investigate processes of con-tjnental rifting and separation of the southwestern Japan Arc. The SouU-i Korea Plateau preserves funda-mental elements of rift architecture comprising a seaward succession of a rift basin and an uplifted rift flank passing into the slope, typical of a passive continental margin. Two distinguished rift basins (Onnuri and Bandal Basins) in the South Korea Plateau are bounded by major synthetic and smaller antithetic faults, creating wide and symmetric profiles. The large-offset border fault zones of these basins have convex dip slopes and demonstrate a zig-zag arrangement along strike. Rifting was primarily controlled by normal faulting resulting from extension orthogonal to the inferred line of breakup along the base ofthe slope rather U-ian strike-slip deformation. Two extension direcdons for rifdng are recog-nized; U-ie Onnuri Basin was rifted in U-ie EW direction; U-ie Bandal Basin in U-ie EW and NW-SE directions, suggesting two rift stages. We interpret that the E-W direction represents initial rifting at the inner margin; while the Japan Basin widened, rifting propagated repeatedly from the Japan Basin to the southeast toward the Korean margin but could not penetrate the strong continental lithosphere of the Korean Shield and changed direction to the south, resulting in E-W extension to create the rift basins at the Korean margin. The Hupo Basin to the south of the Korea Plateau is estimated to have formed in this process. The NW-SE direction probably represents the direction of rifting orthogonal to the inferred line of breakup along the base of the slope of the South Korea Plateau; after breakup the southwestern Japan Arc separated in the SE direction, indicating a response to tensional tectonics associated with the subduction of the Pacific Plate in the NE direction. We suggest that structural evolution of the eastern Korean margin can be explained by the processes occurring at the passive continental margin.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.5
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• pp.667-675
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• 2023

The Spanish mackerel Scomberomorus niphonius is an economically important fish species in the southwestern waters of Korea. This study aimed to provide insights into the reproductive biology of this species in the southwestern waters of Korea. We analyzed monthly changes in fork length (FL), maturity stages, and gonadosomatic index (GSI). Moreover, we measured the in FL at sexual group maturity of 50%, 75%, 97.5%, and sex ratio (female vs. male). The overall sex ratio of female and male was 1:0.8. GSI value showed the highest peak in May; however, the spawning period revealed by the microscopic analysis of gonad tissue of S. niphonius was from April to August 2020. The main spawning seasons for the entire populations was from May to June. The fork length at 50% group maturity was 53.3 cm for females and 53.1 cm for males. These results of spawning period of Spanish mackerel highlight the influences of water temperatures that were higher than those in the past, an increase in resource levels, and the level of Pacific anchovy resources flowing into the spawning ground.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.12a
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• pp.73-83
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• 2007

We interpreted marine seismic profiles in conjunction with swath bathymetric and magnetic data to investigate rifting to breakup processes at the eastern Korean margin that led to the separation of the southwestern Japan Arc. Analysis of rift fault patterns suggests that rifting at the Korean margin was primarily controlled by normal faulting resulting from extension rather than strike-slip deformation. Two extension directions of E-W and NW-SE for rifting are recognized. We interpret that the E-W direction represents initial rifting at the inner margin and the NW-SE direction probably represents the extension in response to tensional tectonics associated with the subduction of the Pacific Plate in the NW direction. No significant volcanism was involved in rifting. In contrast, the inception of sea floor spreading documents a pronounced volcanic phase which appears to reflect asthenospheric upwelling as well as rift-induced convection particularly in the narrow southern margin. We suggest that structural and igneous evolution of the Korean margin, although it is in a back-arc setting, can be explained by the processes occurring at the passive continental margin with magmatism influenced by asthenospheric upwelling.

• Ocean and Polar Research
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• v.23 no.4
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• pp.361-376
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• 2001

The characteristics of SST variability in the East Sea are analyzed using NOAA/AVHRR weekly SST data with about $0.18^{\circ}{\times}0.18^{\circ}$ resolution ($1981{\sim}2000$) and reconstructed historical monthly SST data with $2^{\circ}{\times}2^{\circ}$ resolution $(1950{\sim}1998)$. The distinct feature of wintertime SST is high variability in the western and eastern parts of $38^{\circ}{\sim}40^{\circ}$ latitudinal band, which are the northern boundary of warm current in the East Sea during winter. However, summertime SST exhibits variability with similar magnitude in the entire region of the East Sea. The analysis of remote correlation also shows that SST in the East Sea is closely correlated with that in the region of Kuroshio in winter, but in summer is related with that in the western and eastern regions of the same latitudes. From these results it is postulated that the SST variability in the East Sea may be related with the variations of East Korean Warm Current and Tsushima Warm Current in winter, but in summer probably with the variations of atmospheric components. In the analysis of ENSO related SST anomaly, a significant negative correlation between SST anomalies in the East Sea and SST anomalies in the tropical Pacific is found in the months of August-October (ASO). The SST in the ASO period shows more significant cooling in E1 $Ni\~{n}o$ events than warming in La $Ni\~{n}a$ events. Also, the regional analysis shows by the Student's t-test that the negative SST anomalies in the E1 $Ni\~{n}o$ events are more significant in the southwestern part of the East Sea.

• Economic and Environmental Geology
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• v.45 no.1
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• pp.41-48
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• 2012

A theoretical $CO_2$ storage capacity is estimated on the southwestern continental shelf margin of Ulleung Basin, offshore Korea using 2D/3D multi-channel seismic and wellbore data acquired in the area over the two decades since the late 1980s. For the first time in Korea, the present study applies an efficiency factor to the capacity calculation, together with the other required parameters. For possible $CO_2$ storage volume estimation of the study area, we interpreted the seismic data in the Gorae area from 800 m to 3,000 m below the seafloor integrated with the well data, and identified five different seismic units; the limited depth interval is considered because of fluid state of $CO_2$ and tightness of the formation. The total volumes of each seismic unit were converted with a time-depth relation inferred from the checkshot surveys before the other required parameters including porosity and density were applied to compute the potential storage capacity. The accumulated possible storage volume from the five depositional units in the study area is estimated to be approximately 5,100 Mton ($P_{50}$). The approaches made in this study will be applied to the rest area of the basin and other continental shelves (i.e., Yellow Sea and northern part of East China Sea) in the next phase.

• 한국해양학회지
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• v.29 no.2
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• pp.152-163
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• 1994

The characteristics and fluctuations of structures and spatial distributions of warm eddies (anticyclonic eddies) in the southwestern part of the East Sea (the Japan Sea) are discussed based on the data gathered y the Fisheries Research and Development Agency, Korea from 1967 to 1968. The warm eddies existed very often in the southwest of the Ullung Island. The warm eddies are elliptical in shape and the mean size is about 130 km in diameter. Bimonthly distributions of warm eddies, the largest value of observed frequency and diameter in August and the least in June, indicate that the generation of the warm eddy is related with the development of the East Korean Warm Current. The warm eddies move west, north or southward with 0.80∼2.50 cm/sec or stay over a few months at the same place southwest of the Ullung Island. Movement of warm eddies may be influenced by the neighboring currents, the Rossby wave and the topography. The relationship between the position of warm eddies and the bottom topography suggests that the development and the movement of warm eddies are controlled by the Ullung Basin. The warm eddies should be divided into two groups. One group is the shallow warm eddy with strong baroclinic characteristics and the other is the deep one with strong Barotropic characteristics. The shallow group seems to be closely related with positive values (in summer) of the sea level difference between Pusan and Mozi (the Tsushima Current), while the deep group has no relation with that.

• The Korean Journal of Petroleum Geology
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• v.12 no.1
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• pp.20-26
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• 2006

Late Quaternary stratigraphy and sedimentary environmental changes were studied based on four core sediments and their pore water taken from the southwestern part of the East Sea. The results of tephrostratigraphy and radiocarbon dates indicate that the cores cover the time interval from the middle stage of Marine Isotope Stage (MIS) 3 to MIS 1 (Holocene). The average of sedimentation rate in core sediments varies from 10 cm/kyr to 20 cm/kyr, but it fluctuates generally in particular time intervals such as MIS 2, which would be related with the sea-level changes at that time. On the other hand, the relations between ${\delta}^{13}C_{org}$ and C/N ratios suggest that the organic matter in the cores was originated mainly from marine algae. In addition, the value of ${\delta}^{13}C_{CH4}$ indicates bacterial origin rather than thermogenic one.

• 한국해양학회지
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• v.28 no.1
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• pp.1-16
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• 1993

The monthly mean sea levels at 48 stations located at the East and Yellow Seas coasts of Korea, Russia and Japan are processed to investigate seasonal sea level variations. The strong seasonal variations are found to be at the west coast of Korea (42.1 cm in Kunsan), in the region of the Korea strait and near the southern part of Primorye (30-33 cm); the weak ones near the southwestern coast of the Sakhalin Island (10-12 cm). Practically for the whole study area except the southwest Sakhalin, the general picture of the seasonal sea level changes is alike: the mean sea level rises in summer-autumn and falls in winter-spring. The spectral analysis of the records also shows that the seasonal oscillations strongly dominate in the sea level variations, more than 80% or total energy in the southern part of the investigated region and 50-70% in the northern part relate to these oscillations. The annal peak significantly prevails in spectra of the monthly sea levels for the majority of stations, the semiannual peak is also well manifested, but the seasonal peaks of higher order (corresponding to the periods of four and three months) reveal only at some records. The maximal amplitudes of annual component by a least square method are found at the Yellow Sea coast of Korea (20-21 cm) and also near the Japanese coast of the korea Strait (19-19 cm). The semiannual component has the maximal amplitudes (3-4 cm) near the south and southwestern coasts of the Sakhalin Island. The annual range of the sea levels is much weaker here than in the other regions, the relative investment of the seasonal oscillations in total energetic budget is only 35-40%, annual ($A_1$) and semiannual ($A_2$) components have nearly the same amplitude (seasonal factor $F=A_1/A_2=0.9-1.2$). On the basis of the present examination on sea level changes together with the results of Tomizawa et. al.(1984) the whole investigated area may be divided into 10 subregions, 2 of them are related to the Yellow Sea and Western part of the Korea Strait (Y1, Y2), the other ones (E1-E8) to the East Sea.

• Journal of the korean society of oceanography
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• v.39 no.1
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• pp.26-34
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• 2004

The evolution of intricate and striking patterns of suspended sediments (SS), which are created by certain physical dynamics in the East China and Yellow Seas, has been investigated using satellite ocean color imageries and vertical profiles of particle attenuation and backscattering coefficients. The structure of these patterns can reveal a great deal about the process underlying their formation. Sea surface temperature (SST) analyzed from the Advanced Very High Resolution Radiometer (AVHRR) thermal infrared data were used to elucidate the physical factors responsible for the evolution of suspended sediment patterns in the East China Sea. The concomitant patterns of suspended sediments were tracked from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color data. The detailed examination about these patterns gave birth to the definition of the evolution of suspended sediments (SS) into four stages: (1) Youth or Infant stage, (2) Younger stage, (3) Mature stage, and (4) Old stage. We describe about the three directional forces of the tidal currents, ocean warm currents and estuarine circulations that lead to occurrence of various stages of the evolution of suspended sediments that increase turbidity at high levels through out the water column of the inner and outer shelf areas during September to April. The occurrence of these four stages could be repeatedly observed. In contrast, vertical profiles of the particle attenuation ($c_{p}$) and backscattering ($b_{bp}$) coefficients displayed obvious patterns of the propagation of suspended sediment plume from the southwestern coastal sea that leads to eventual collision with the massive sediment plume originating from the Yangtze banks of the East China Sea.