• Journal of the Korean earth science society
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• v.33 no.6
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• pp.497-509
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• 2012

The Gochanggun Kwangseungri macro-tide open-coast beach, located in the southwestern coast of Korea, was investigated in terms of the seasonal variations of surface sediment facies and sedimentary environment. Surface sediments of 45 sites in four seasons (May 2006 - February 2007) were sampled along three survey lines (15 sites in each survey line). The surface sediments of the Kwangseungri Beach are mainly composed of fine-grained sands, and its mean grain size is the coarsest in winter. Mud facies partly exists in summer, whereas it is nearly absent in winter. The spatial distribution of surface sediments shows a coast-parallel band of fine and medium sands during spring, fall, and winter. In the northern part, the study area is dominated by fine sands during summer, whereas by coarse sands during winter. These results can be interpreted that tide is more effective than wave on the surface sediment distribution of the Kwangseungri Beach during the summer season.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.2
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• pp.70-80
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• 2014

We carried out numerical experiments to understand sedimentary environments in Gamak Bay where is located in the center of the southern coast of Korea. Deposition rates in Gamak Bay appeared to increase in the autumn and spring whereas they appeared to decrease in the summer and winter. These seasonal variations qualitatively coincided with seasonal variations of Ignition Loss (IL) for surface sediments. Furthermore, deposition rates turned out to be prevalent compared to erosion rates in most areas of the bay. On the other hand, current measurement results at both the northeast and south mouths of the bay showed their residual components to flow into the bay. Therefore, we can conclude that contaminated materials flowing into Gamak Bay will precipitate to be deposited in the bay as long as there is no specific events such as dredging.

• Geophysics and Geophysical Exploration
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• v.16 no.4
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• pp.203-210
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• 2013

To look into site characteristics of the Hwacheon borehole seismic station, we analyzed property of earthquake and microtremor recorded on surface and borehole seismometers. Acoording to analysis result of microtremor, the surface-to-borehole energy ratio was approximately 15 times greater during the daytime than during the nighttime, and the surface-to-borehole ratios of spectral amplitudes as frequency increases. For earthquake data, amplitude spectra and dominant frequency were computed using surface and borehole data. As a result, small earthquakes with short distance recorded on surface seismometer peaked at 8 Hz, 46 Hz. This result corresponds to resonance frequencies (7.4 Hz, 46 Hz) calculated by H/V spectral ratio. We confirmed amplification effect by site characteristics of overburden. Background noise level was approximately 20,000 times smaller at borehole seismic station than surface seismic station. These results provide strong evidence for the superior recording of earthquakes using borehole seismometers instead of surface seismometers.

• Korean Journal of Environmental Biology
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• v.36 no.2
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• pp.107-116
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• 2018

In this study, the distribution of sedimentary environment and benthic macro-fauna in habitats and non-habitats of Zostera marina were investigated. The purpose of this study was to obtain basic data about the sedimentary environment and benthic macro-fauna in the habitats and non-habitats of Z. marina. Sand was dominant within habitat environments, whereas the non-habitats were predominantly composed of silt. As a result, the habitats of Z. marina have a different grain size and organic matter content compared to the non-habitats. These differences in the sedimentary environment were expected to influence the species composition of benthic animals. Benthic communities in the habitats of Z. marina showed a higher density and a greater number of species than in the non-habitats. As a result of an ecological index evaluation, the species diversity index (H') was $3.44{\pm}0.10$ for the habitat; the non-habitat was analyzed as $2.34{\pm}0.35$. It was also found that the stability of community in the habitats was higher than that in the non-habitats. The cluster analysis also clearly showed that habitats and non-habitats of Z. marina have distinct characteristics.

• Applied Chemistry for Engineering
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• v.31 no.5
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• pp.481-486
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• 2020

To evaluate geochemical characteristics of surface sediments in Samcheok Port, the distribution characteristics of particle sizes, organic matters and heavy metals were investigated. The sediments showed a mixed property of sand, silt, and clay, however fine-grains dominated at the inner port and coarse-grains dominated at the outer port. The organic (COD, TOC, and IL) contamination of the sediment at the inner port were higher than that of the outer port, and the concentrations of total nitrogen and total phosphorus at the inner port was higher than those of the outer port. Also, heavy metals contamination of surface sediments at the inner port was higher than those of the outer port (except for As). From the results of high organic matter concentrations and C/N ratio at the inner port, it is considered that the contamination of organic matters was mainly derived from the land. The correlation analysis among the particle size, chemical composition, and heavy metals resulted in high correlation between silt-clay and heavy metals, and between organic matters and heavy metals. The sequential extraction results of heavy metals showed the sum of exchangeable, carbonate, and oxide fractions of Ni, Zn, Cu, Pb, Cd, and As were 14.8, 49.8, 39.1, 32.2, 51.8 and 26.6%, respectively.

• Journal of the Korean earth science society
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• v.31 no.7
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• pp.708-719
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• 2010

The Gochang-gun Dongho macro-tide pocket-type beach, located on the southwestern coast of Korea, is investigated in terms of the seasonal variations of surface sediment and sedimentary environment. Surface sediments of 45 sites in four seasons (May 2006-February 2007) are sampled across three survey lines (15 sites in each survey line). The surface sediments of the Dongho Beach are mainly composed of fine to coarse sands, and the ratio of fine sand is the largest. The average of grain size is the coarsest in the summer. The spatial distribution of surface sediments shows a coast-parallel band of fine and medium sands during three seasons of spring, fall, and winter, whereas medium sands dominated in the northern part of the study area during the summer. These results suggest that a tide is more effective than a wave in the surface sediments of the Dongho Beach during the summer.

• 한국해양학회지
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• v.21 no.4
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• pp.236-244
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• 1986

This study was carried out for appreciable information on the proper habitats and feeding modes of some dominant polychaetes in the continental shelf of the East Sea during April, 1985. Among 95 polychaete species, we select ed 9 dominant species in terms of their occurring frequency, abundance and population density. These are Terebellides stroemi, Chaetozone setosa, Magelona japonica, Ampharete arctica, Aglaophamus sinensis, Nothria holobranchiata, Lumbrineris japonica, Myriochele gracilis, Notoproctus pacificus. Major food item s of these species are centric diatoms and detritus. The feeding modes of the the m are mainly surtace or subsurface deposit feeding, though two specters, M.holobranchiata and L. japonica, could be assumed to be potential carnivores. To a certain degree, most deposit feeders in the coarse sediments showed selectivity in feeding and tube building. The feeding mode, gut content and the tube structure, and the distribution pattern of dominant polychaetes correspond well with the habitat tharacters, e.g.the bottom topography, the source of food and the sediment composition.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.4
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• pp.312-322
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• 1999

We have studied both submarine morphology and sediment characteristics of waste disposal sites in the southwestern Ulleung Basin, East Sea, as part of a marine environmental preservation program. The Jung waste disposal site in the outer shelf is characterized by the thick accumulation of coarse-grained palimpsest sediments and fine-grained sediments from various sources. The Byung waste disposal site in the continental slope is generally characterized by hemipelagic muds with intermittent sandy sediments originated from the outer shelf and upper slope. The hemipelagic sediments, draping the seafloor, consist of fluidized muds. The core sediments show numerous bioturbation structures which cause vertical mixing of sediments. The surface sediments can be divided into four sand types (S-1, S-2, S-3, and S-4) and two mud types (M-1 and M-2) based on relative contents of reworked coarse-grained palimpsest sediments and fine-grained sediments. sorting and heavy mineral contents. The sands are probably relict sediments reworked during high-energy conditions such as typoon or storm. On the other hand, the muds were originated from various sources such as recent input from the Nakdong River, reworked fine-grained sediment from the shelf or suspended particulate matter from the East Sea Warm Current.

• Economic and Environmental Geology
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• v.45 no.5
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• pp.513-523
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• 2012

The upper sedimentary layer of the Ulleung Basin in the East Sea shows stacked mass-flow deposits such as slide/slump deposits in the upper slope, debris-flow deposits in the middle and lower slope, and turbidites in the basin plain. Shallow gases or gas hydrates are also reported in many area of the Ulleung Basin, which are very important in terms of marine resources, environmental changes, and geohazard. This paper aims at studying acoustic characteristics and distribution pattern of gas-related structures such as acoustic column, enhanced reflector, dome structure, pockmark, and gas seepage in the upper sedimentary layer, by analysing high-resolution chirp profiles. Acoustic column shows a transparent pillar shape in the sedimentary layer and mainly occurs in the basin plain. Enhanced reflector is characterized by an increased amplitude and laterally extended to several tens up kilometers. Dome structure is characterized by an upward convex feature at the seabed, and mainly occurs in the lower slope. The pockmark shows a small crater-like feature and usually occurs in the middle and lower slope. Gas seepage is commonly found in the middle slope of the southern Ulleung Basin. These gas-related structures seem to be mainly caused by gas migration and escape in the sedimentary layer. The distribution pattern of the gas-related structures indicates that formation of these structures in the Ulleung Basin is controlled not only by sedimentary facies in upper sedimentary layer but also by gas-solubility changes depending on water depth. Especially, it is interpreted that the chaotic and discontinuous sedimentary structures of debris-flow deposits cause the facilitation of gas migration, whereas the continuous sedimentary layers of turbidites restrict the vertical migration of gases.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.761-770
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• 2014

In september 2004 and 2006, topographical and sedimentological survey were carried out using multibeam echosounder, which were to investigate shape characteristics, temporal changes and control factors of the subaqueous dunes in the southern Gyeonggi Bay. The present tidal current and sedimentary characteristics of study area make conditions that the sizes (length and height) of large subaqueous dunes are developed and maintained sufficiently. The change of sedimentary characteristics over time, the decrease in grain size causes reduction in the height of very large subaqueous dunes. Therefore it shows that the grain size of surface sediments is a primary control factor in defining subaqueous dune sizes in the study area.