• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.5
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• pp.335-347
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• 2013

In February 2008, high storm waves due to a developed atmospheric low pressure system propagating from the west off Hokkaido, Japan, to the south and southwest throughout the East Sea (ES) caused extensive damages along the central coast of Japan and along the east coast of Korea. This study consists of two parts. In the first part, we estimate extreme storm wave characteristics in the Toyama Bay where heavy coastal damages occurred, using a non-hydrostatic meteorological model and a spectral wave model by considering the extreme conditions for two factors for wind wave growth, such as wind intensity and duration. The estimated extreme significant wave height and corresponding wave period were 6.78 m and 18.28 sec, respectively, at the Fushiki Toyama. In the second part, we perform numerical experiments on wave-structure interaction in the Fushiki Port, Toyama Bay, where the long North-Breakwater was heavily damaged by the storm waves in February 2008. The experiments are conducted using a non-linear shallow-water equation model with adaptive mesh refinement (AMR) and wet-dry scheme. The estimated extreme storm waves of 6.78 m and 18.28 sec are used for incident wave profile. The results show that the Fushiki Port would be overtopped and flooded by extreme storm waves if the North-Breakwater does not function properly after being damaged. Also the storm waves would overtop seawalls and sidewalls of the Manyou Pier behind the North-Breakwater. The results also depict that refined meshes by AMR method with wet-dry scheme applied capture the coastline and coastal structure well while keeping the computational load efficiently.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.15 no.2
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• pp.72-85
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• 2010

Seasonal variation in species composition of estuarine fauna in the Han River estuary was determined using monthly samples collected near Ganghwa Island by a bag net from February to December 2009. Total number of species was 86: 54 species of fishes, 16 species of shrimps of crustacean, 12 species of other crustacean such as craps and so on, 3 species of cephalopods and 1 species of jellyfish. Of a total of 86 species, Palaeman carinicauda (32.6%), Acetes japonicus (15.9%), Palaemon gravieri (9.9%), Portunus trituberculatus (7.7%) and Acetes chinensis (6.9%) were predominated in abundance. These 5 crustacean accounted for 73% of total. Abundance, biomass and diversity of Han River estuarine fauna were high in spring and autumn, indicating typical pattern of temperate area. Out of dominant species, the brackish residence species such as Coilia nasus, Chelon haematocheilus, Mugil cephalus, Synechogobius hasta, Lophiogobius ocellicauda, Tridentiger barbatus, Palaeman carinicauda, Palaemon gravieri were collected almost year-round and predominated in abundance. Coastal migratory fauna species such as Coilia mystus, Thryssa hamiltonii, Thryssa adelae, Sardinella zunasi, Engraulis japonicus, Portunus trituberculatus, Acetes japonicus, Collichthys lucidus, Pampus argenteus were most plentiful from spring through autumn. Their adult coastal migratory entered the estuary in spring and large numbers of their juveniles were grew in summer and autumn until moving out to deeper waters for over-wintering, indicating they use estuary as nursing ground. Diadromous fish such as Anguila japonica adults were collected in autumn during their downstream migration. Brackish fauna and crustacean, especially shrimps were predominant, and few contaminant indicator species collected in the Han River estuary, indicating this area maintains the characteristics of natural estuary ecosystem.

• Economic and Environmental Geology
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• v.37 no.5
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• pp.569-583
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• 2004

The rock properties of the West pagoda in the Gameunsaji temple site are composed mainly of dark grey porphyritic granodiorite with medium grained equigranular texture and developed with small numerous dioritic xenoliths. These xenoliths occurred with small holes due to different weathering processes. As a weathering results, the rock properties of this pagoda occur wholly softened to physical hardness because of a complex result of petrological, meteorological and biological causes. Southeastern part of the pagoda deteriorated seriously that the surface of rock blocks showed partially exfoliations, fractures, open cavities in course of granular decomposition of minerals, sea water spray and crystallization of salt from the eastern coast. The Joint between blocks has small or large fracture cross each other, contaminated and corrupted for inserting with concrete, cement mortar, rock fragments and iron plates, and partially accelerated coloration and fractures. There are serious contamination materials of algae, fungus, lichen and bryophytes on the margin and the surface on the roof stone of the pagoda, so it'll require conservation treatment biochemically for releasing vegetation inhabiting on the surface and the discontinuous plane of the blocks because of adding the weathering activity of stones and growing weeds naturally by soil processing on the fissure zone. Consisting rock for the conservation and restoration of the pagoda would be careful choice of new rock properties and epoxy to reinforce for the deterioration surfaces. For the attenuation of secondary contamination and surface humidity, the possible conservation treatments are needed.

• The Korean Journal of Petroleum Geology
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• v.13 no.1
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• pp.1-16
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• 2007

The southeastern Korean Peninsula has experienced crustal multi-deformations according to changes of global tectonic setting during the Cenozoic. Characteristic features of the crustal deformations in relation to major Cenozoic tectonic events are summarized as follows. (1) Collision of Indian and Eurasian continents and abrupt change of movement direction of the Pacific plate (50${\sim}$43 Ma): The collision of Indian and Eurasian continents caused the eastward extrusion of East Asia block as a trench-rollback, and then the movement direction of the Pacific plate was abruptly changed from NNW to WNW. As a result, the strong suction-force along the plate boundary produced a tensional stress field trending EW or WNW-ESE in southeastern Korea, which resultantly induced the passive intrusion of NS or NNE trending mafic dike swarm. (2) Opening of the East Sea (25${\sim}$16 Ma): The NS or NNW-SSE trending opening of the East Sea generated a dextral shear stress regime trending NNW-SSE along the eastern coast line of the Korean Peninsula. As a result, pull-apart basins were developed in right bending and overstepping parts along major dextral strike slip faults trending NNW-SSE in southeastern Korea. The basins can be divided into two types on the basis of geometry and kinematics: Parallelogram-shaped basin (rhombochasm) and wedged-shaped basin (sphenochasm), respectively. In those times, the basins and adjacent basement blocks experienced clockwise rotation and northwestward tilting contemporaneously, and the basins often experienced a kind of propagating rifting from NE toward SE. At about 17Ma, the Yonil Tectonic Line, which is the westernmost border fault of the Miocene crustal deformation in southeastern Korea, began to move as a major dextral strike slip fault. (3) Clockwise rotation of southeastern Japan Island (about 15 Ma): The collision of the Izu-Bonin Arc and southeastern Japan Island, as a result of northward movement of the Philippine sea-plate, induced the clockwise rotation of southeastern Japan Island. The event caused the NW-SE compression in the Korea Strait as a tectonic inversion, which resultantly tenninated the basin extension and caused local counterclockwise rotation of blocks in southeastern Korea. (4) E-W compression in the East Asia (after about 5 Ma): Decreasing subduction angle of the Pacific plate and eastward movement of the Amurian plate have constructed the-top-to-west thrusts and become a major cause for earthquakes in southeastern Korea until the present time.

• The Journal of the Petrological Society of Korea
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• v.23 no.2
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• pp.45-59
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• 2014

This study has been designed to collate distribution, morphology, petrology of columnar joint in South Korea. Reported columnar joint areas in South Korea are 68, until the present time. These can be divided into five group by geography and volcanic activity. 1) The 16 columnar joint areas are distributed in Hantangang region. The 15 areas in this region are composed of basaltic lava in the Quaternary period, and the other 1 area is composed of volcanic rocks in the Cretaceous period. 2) The 18 columnar joint areas are distributed in Jeju island. Most of them are composed of basaltic lava(alkali basalt and Hawaiite), and the Sanbangsan and Baegrokdam area are composed of trachyte in the Quaternary period. Colonnade, entablature and chisel mark of the columnar joint are typically occur in basaltic lava. 3) The 5 columnar joint areas are distributed into the Ulleung island and Dokdo including Guksubawi. These are consisted of relatively well-formed trachyte columns in the Quaternary period. 4) The 8 columnar joint areas are distributed into the Pohang, Gyeongju and Ulsan region and consist of the Tertiary period volcanic rock. It's shape are dome, radial, horizontal and vertical. The 4 columnar joint areas are reported in the Pyeongtaek and Asan city of Chungcheongnamdo and Gosung of Gangwondo. All of them are the Tertiary period basalt. 5) The 15 columnar joint areas are distributed into the west and south coast region. Those are consisted of various rock type(from basalt to dacite), various occurrences(lava flow to welded tuff), and various diameters(20 cm to several meters). The columnar joint of Mudeung mountain and Juwang mountain are welded tuff in the Cretaceous period. The columnar joint is distributed over a wide area in South Korea, 5 in Gangwondo, 13 in Gyeonggido, 2 in Chungnam, 14 in Gyeongbuk, 1 in Jeonbuk, 10 in Jeonnam, 5 in Gyeongnam, and 18 in Jeju. The columnar joints in South Korea can be arranged in order of formative period, 18 in the Cretaceous period, 12 in the Tertiary period, and 38 in the Quaternary period. By magma series, 36 are belong to alkaline series and 32 are belong to sub-alkaline series.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.2
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• pp.105-118
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• 2000

Anchored measurements (12.5 hr) of suspended sediment concentration and other hydrodynamic parameters were carried out at two stations located at the entrance to Hampyung Bay in summer (August 1999). Tidal variations in water temperature and salinity were in the range of 26.0-27.9$^{\circ}C$ and 30.9-31.5, respectively, indicating exchange offshore and offshore water mass. Active tidal mixing processes at the entrance appear to destroy the otherwise vertical stratification in temperature and salinity in spite of strong solar heating in summer. On the contrary, suspended sediment concentrations show a marked stratification with increasing concentrations toward bottom layer. Clastic particles in suspended sediments consist mostly of very fine to fine silt (4-16 ${\mu}$m) with a poorly-sorted value of 14.7-25.9 ${\mu}$m. However, at slack time with less turbulent energy, flocs larger than 40 ${\mu}$m are formed by cohesion and inter-collision of particles, resulting in a higher settling velocity. Strong ebb-dominated and weak flood dominated tidal currents, in the southwestern and the northeastern part, respectively, result in a seaward residual flow of -10${\sim}$-20 cm $s^{-1}$ at station H1 and a bayward residual flow less than 5.0 cm $s^{-1}$ at station H2. However, mean concentration of suspended sediments at station H1 is higher at flood (95.0-144.1 mg $1^{-1}$) than in ebb (75.8-120.9 mg $1^{-1}$). On the contrary, at the station H2, the trend is reversed with higher concentration at the ebb (84.7-158.4 mg $1^{-1}$) than that at the flood (53.0-107.9 mg $1^{-1}$). As a result, seaward net suspended sediment fluxes ($f_{s}$) are calculated to be -1.7 ${\sim}$-$15.610^{3}$ kg $m^{-2}$ $s^{-1}$ through the whole water column. However, the stations H1 and H2 show definitely different values of the flux with higher ones in the former than in the latter. Alternatively, depth-integrated net suspended sediment loads ($\c{Q}_{s}$) for one tidal cycle are also toward the offshore with ranges of 0.37${\times}$$10^{3}$ kg $m^{-1}$ and 0.21${\times}$$10^{3}$ kg $m^{-1}$, at station H1 and H2, respectively. This seaward transport of suspended sediment in summer suggests that summer-time erosion in the Hampyung muddy tidal flats is a rather exceptional phenomenon compared to the general deposition reported for many other tidal flats on the west coast of Korea.

• Economic and Environmental Geology
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• v.52 no.6
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• pp.561-571
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• 2019

The Hupo Basin, continental marginal basin, of the East Sea extends to Uljin-gun and Yeongdeok-gun. The Hupo Bank, a terrain that is higher than the surrounding seabed, is located at the eastern boundary of the Hupo Basin. KIOST(Korea Institute of Ocean Science and Technology) conducted detailed bathymetry surveys in the northern, central and southern areas of the Hupo Basin from 2011 to 2013. The Hupo Basin, bounded by steep slopes of the Hupo Bank, is deepened from the west coast to the east and deepest to a maximum depth of about 250 m. A narrow seafloor channel appears in the northern, central, and southern areas with the deepest depths. Numerous pockmarks appear on the seafloor at depths of about 150 ~ 250 m in all the three areas of the detailed bathymetry surveys. These pockmarks generally have diameters of about 20 to 50 m and depths of about 4 to 6 m, with craterlike submarine topography of various sizes. Seafloor sediments in the pockmark areas consist of fine silt. Comparing the shape and size of the pockmark of the Hupo Basin with that of other regions of the world, it is considered to be classified as a normal pockmark. There are about 7 pockmarks/1 ㎢ in the northern part of the three areas and about 8 pockmarks/1 ㎢ in the central part. The southern part has about 5 pockmarks/1 ㎢. If the area with the possibility of pockmarks is extended to the depth area of about 150 ~ 250 m in the entire Hupo Basin, the number of pockmarks is estimated to be more than about 4800. The pockmark of the Hupo Basin is more likely to be generated by a fluid such as a liquid than a gas. But it is necessary to scrutinize the cause and continuously monitor the pockmark.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.19 no.1
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• pp.8-34
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• 2014

We reviewed foreign evaluation systems based on the macrobenthic and macroalgal communities and developed a system, composed of a set of ecological indices able to evaluate the functionality (FI, Functional Index; estimation of stability and productivity) and maturity (MI, Maturity Index; comparisons with biological parameters of natural reefs) of artificial reefs by comparing the status in the adjacent natural reefs in Korean coastal waters. The evaluation system was applied to natural and artificial reefs/reef-planned areas (natural reefs), established in the 5 marine ranching areas (Bangnyeong-Daechung, Yeonpyung, Taean, Seocheon and Buan) in the west coast of Korea. The FI ranged between 31.6 (Bangnyeong-Daechung) and 72.5% (Buan) and MI did between 53.1 (Seocheon) and 76.9% (Taean) in average. The evaluation of artificial reefs by the two indices, showed the most appropriate status in Taean. The FI between the adjacent artificial and natural reefs were in significant linear relationship ($r^2=0.83$, p=0.01). This indicated the local status of biological community may be critical in determining the functionality of the artificial reefs. We have suggested an integrative but preliminary evaluation system of artificial reefs in this study. The output from the evaluation system may be utilized as a tool for environment/resource managers or policy makers, responsible for effective use of funds and decision making. Given the importance, we need to use the options to enhance and improve the accuracy as follows: (1) continuous validation of the evaluation system and rescaling the criteria of indicators, (2) vigorous utilization of observation and experience through the application and data accumulation and (3) development and testing of brand-new indicators.

• Economic and Environmental Geology
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• v.49 no.6
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• pp.417-432
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• 2016

It was firstly revealed in this research that the marine terrace of the Ijin-ri (Bukpyung-myeon, Haenam-gun) was formed during the last interglacial (Marine Isotope Stage 5e; MIS 5e). The marine terrace totally ranging from 4.8 m (asl) to 8.8 m (asl) is subdivided into 4 units; Unit I ranges 4.8-5.3 m, unit II ranges 5.3-6.9 m, unit III ranges 6.9-8.3 m, and unit IV ranges 8.3-8.8 m. Strong evidences that units II and III were formed during MIS5e were obtained based on OSL dating, the physical characterizations such as particle size distribution, magnetic susceptibility and water content, principal element and trace element analyses, and quantitative clay mineral analysis for samples at the 30 cm intervals. The rounded gravels on the marine terrace are regarded to be originated from the clastic materials transported directly from the surrounding mountains toward the marine and abraded in the coastal area, without any fluvial processes. During the warmest period (125k, unit II), the increase in rainfall, along with the rapid rise in sea level, was likely caused the high amount of clastic materials transported to the upper part of the beach. As a result of comparing clay mineral ratios of study site with those derived from sediments of either tidal flats, or the Yellow Sea, it is interpreted that the sediments of study site were influenced from the marine. The results will be used to investigate the hydrological activity and sedimentary environment during the high sea level in the past.

• Journal of the Korean earth science society
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• v.36 no.1
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• pp.68-81
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• 2015

In this study, the correlation between the frequency of summer tropical cyclones (TC) affecting areas around Korea over the last 37 years and the western North Pacific monsoon index (WNPMI) was analyzed. A clear positive correlation existed between the two variables, and this high positive correlation remained unchanged even when excluding El Ni$\tilde{n}$o-Southern Oscillation (ENSO) years. To investigate the causes of the positive correlation between these two variables, ENSO years were excluded, after which the 8 years with the highest WNPMI (positive WNPMI phase) and the 8 years with the lowest WNPMI (negative WNPMI phase) were selected, and the average difference between the two phases was analyzed. In the positive WNPMI phase, TCs usually occurred in the eastern waters of the tropical and subtropical western North Pacific, and tended to pass the East China Sea on their way north toward Korea and Japan. In the negative WNPMI phase, TCs usually occurred in the western waters of the tropical and subtropical western North Pacific, and tended to pass the South China Sea on their way west toward the southeastern Chinese coast and the Indochina peninsula. Therefore, TC intensity was higher in the positive WNPMI phase, during which TCs are able to gain sufficient energy from the sea while moving a long distance to areas nearby Korea. TCs also tended to occur more often in the positive WNPMI phase. In the difference between the two phases regarding 850 and 500 hPa streamline, anomalous cyclones were reinforced in the tropical and subtropical western North Pacific, while anomalous anticyclones were reinforced in mid-latitude East Asian areas. Due to these two anomalous pressure systems, anomalous southeasterlies developed in areas near Korea, with these anomalous southeasterlies playing the role of anomalous steering flows making the TCs head toward areas near Korea. Also, due to the anomalous cyclones developed in the tropical and subtropical western North Pacific, more TCs could occur in the positive WNPMI phase.