• Geophysics and Geophysical Exploration
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• v.16 no.4
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• pp.240-249
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• 2013

The seismic data quality of marine geological and engineering survey deteriorates because of the sea swell. We often conduct a marine survey when the swell height is about 1 ~ 2 m. The swell effect correction is required to enhance the horizontal continuity of seismic data and satisfy the resolution less than 1 m. We applied the swell correction to the 8 channel high-resolution airgun seismic data and 3.5 kHz subbottom profiler (SBP) data. The correct sea bottom detection is important for the swell correction. To detect the sea bottom, we used maximum amplitude of seismic signal around the expected sea bottom, and picked the first increasing point larger than threshold value related with the maximum amplitude. To find sea bottom easily in the case of the low quality data, we transformed the input data to envelope data or the cross-correlated data using the sea bottom wavelet. We averaged the picked sea bottom depths and calculated the correction values. The maximum correction of the airgun data was about 0.8 m and the maximum correction of two kinds of 3.5 kHz SBP data was 0.5 m and 2.0 m respectively. We enhanced the continuity of the subsurface layer and produced the high quality seismic section using the proper methods of swell correction.

• 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.

• Economic and Environmental Geology
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• v.38 no.6 s.175
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• pp.689-697
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• 2005

Mineralogical composition, $^{137}Cs$ activity, total organic carbon (TOC), and particle size of marine sediments near Wuljin Nuclear Powerplant were analyzed and the relationships among those components were investigated. The particle sizes of sediments were equivalent to sand size and in the range of $-0.48\~3.6\;Md\phi$. TOC contents and $^{137}Cs$ activities were in the range of $0.06\~1.75\%$ and minimum detectable activity (MDA) $\~4.0Bq/kg-dry$ with the average value of $1.15{\pm}0.62$ Bq/kg-dry, respectively. The sediments in study area were characterized by large particle size and small TOC contents, and $^{137}Cs$ activity compared with other marine sediments. The main mineral components were quartz and feldspar (albite, microcline, and small amount of orthoclase) with small amount of pyroxene, calcite, hornblende. Minerals with $10{\AA}$ XRD peak (mainly biotite) and chlorite were also identified. Among those minerals, biotite shows the linear relationship with $^{137}Cs$ content probably due to the frayed edge site (FES) on biotite or small amount of mixed illite. However, TOC content shows most linear relationship with $^{137}Cs$ content because no significant amount of clay minerals, which can adsorb significant amount of Cs, were observed in the study area, indicating that the distribution of $^{137}Cs$ in this study area was more significantly affected by the TOC content than mineral composition.

• Economic and Environmental Geology
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• v.39 no.3 s.178
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• pp.235-253
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• 2006

We interpreted marine seismic profiles in conjunction with swath bathymetric and magnetic data to investigate rifting to breakup processes at the Korean margin leading to the separation of the Japan Arc. The Korean margin is rimmed by fundamental elements of rift architecture comprizing a seaward succession of a rift basin and an uplifted rift flank passing into the slope, typical of a passive continental margin. In the northern part, rifting occurred in the Korea Plateau, a continental fragment extended and partially segmented from the Korean Peninsula, that provided a relatively broader zone of extension resulting in a number of rifts. Two distinguished rift basins (Onnuri and Bandal Basins) in the Korea Plateau we 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. In contrast, the southern margin is engraved along its length with a single narrow rift basin (Hupo Basin) that is an elongated asymmetric half-graben. Rifting at the Korean margin was primarily controlled by normal faulting resulting from extension in the west and southeast directions orthogonal to the inferred line of breakup along the base of the slope rather than strike-slip deformation. Although rifting involved no significant volcanism, the inception of sea floor spreading documents a pronounced volcanic phase which seems to reflect slab-induced 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 can be explained by the processes occurring at the passive continental margin with magmatism intensified by asthenospheric upwelling in a back-arc setting.

• Economic and Environmental Geology
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• v.34 no.4
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• pp.375-383
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• 2001

We extracted sea surface heights(SSH) from the TopexJPoseidon(T/P) radar altimeter data to compare with fhe SSH estimated from in-situ lide gauges(T/G) at Ulleungdo, Pohang, and SockcholMucko sites. Selection criteria such as wet/dry troposphere, ionosphere, and ocean tide were used to estimate accurate SSH. For time series analysis, the one-hour interval tide gauge SSHs were resampled al lO-day interval of the satellite SSHs. The ocean tide model applied in the altimeter data processing showed periodic aliasings of 175.5 day, 87.8 day, 62J day, 58.5 day, 49.5 day and 46.0 day, and, hence, the ZOO-day filtering was applied to reduce these spectral noises. Wavenumber correlation analysis was also applied to extract common components between the two SSHs, resulting in enhancing the correlation coefficient(CC) dramatically. The original CCs between the satenite and tide gauge SSHs are 0.46. 0.26, and 0.]5, respectively. Ulleungdo shows the largest cc bec;luase the site is far from the coast resulting in the minimun error in the satellite observations. The CCs were then increased to 0.59, 030, and 0.30, respectively, after 200.day filtering, and to 0.69, 0.63. and 0.59 after removing inversely correlative components using wavenumber correlation analysis. The CCs were greatly increased by 87, 227, and 460% when the wavenumber correlation analysis was followed by 2oo-day filtering, resulting in the final CCs of 0.86, 0.85, 0.84, respectively. It was found that the best SSHs were estimated when the two methods were applied to the original data. The low-pass filtered TIP SSHs were found to be well correlated with the TIG SSHs from tide gauges, and the best correlation results were found when we applied both low-pass filtering and spectral correlation analysis to the original SSHs.

• Economic and Environmental Geology
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• v.39 no.1 s.176
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• pp.63-74
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• 2006

In order to identify the Pb pollution and its sources in continental shelf and slope areas, Pb concentration and Pb isotope ratios ($^{207}Pb/^{206}Pb\;and\;^{208}Pb/^{206}Pb$) were determined far 6 box corer sediments collected from the southern East/japan Sea. Pb concentration, and $^{207}Pb/^{206}Pb\;and\;^{208}Pb/^{206}Pb$ ratios were constant at around $25\pm5 ppm$ and 0.842 and 2.092 from 1700 to 1930 year, respectively and increased steadily up to $40\pm5 ppm$ and 0.867 and 2.123 at the beginning of 1990s', respectively. The increase of concentration and isotope ratios in the labile fraction (leached by 2M HC1+0.5M $HNO_3$) explains their increase in bulk sediments, while Pb concentration and isotope ratios in the residual fraction were nearly constant during 300yrs. Temporal variation of Pb isotope ratios was explained by simple two end-members mixing of geo-genic and anthropogenic sources because isotope ratios and the inverse of Pb concentration showed the good linear relationships. Using Pb isotope ratios, we can constrain two Pb sources in the study area. The one is atmospheric particulates, compared with mean values of isotope ratios in atmospheric particulates collected at Jeju and Oki ;stands, based on the history of Pb emmission in Korea and China, and judged by oceanographic processes capable of homogenizing many sources. The other is local sources related to iron mills, refineries of Pb ore and of petroleum located at the coast of the study area. Isotope ratios of anthropogenic Pb can be estimated using two end-members mixing equation and were $0.879\pm0.005\;and\;2.144\pm0.008$ before 1950s' while they increased up to $0.900\pm0.008\;and\;2.162\pm0.011$ after 1980s', respectively.

• Economic and Environmental Geology
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• v.43 no.1
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• pp.1-12
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• 2010

Geochemical approaches on the two recovered piston cores were performed to understand the characteristics of organic matters and the influence of the sea level variation of the East Sea in the Hupo Basin since the Holocene. The analyzing results on organic components (TOC and TN), and isotopic compositions of organic matters showed the variation to core locations and sampling depths. In core 08HZP-01, their values were gradually changed with depth from 4 mbsf to seafloor. However, rapid variation was observed at the boundary of 4.71 mbsf (meter below seafloor) in core 08HZP-03. Based on TOC/TN, $\delta^{13}C_{org}$ and $\delta^{15}N_{org}$, the origin of organic matters in the Hupo Basin can be divided into three groups; 1) predominant marine algae, 2) $C_3$ land plant, and 3) mixture of $C_3$ land plant and marine/freshwater algae. It is likely that the vertical and spatial variations of organic and isotopic compositions reflect the shifts in sedimentary environment (including sediment transportation) by ocean currents and sea-level changes and others during the Holocene period.

• Economic and Environmental Geology
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• v.40 no.5
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• pp.651-660
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• 2007

Acid drainage has been recognized as an environmental concern in abandoned mine sites for long time. Recently, the environmental and structural damage by acid drainage is a current issue in construction sites in Korea. Here, the author introduces the type of damages by acid drainage in construction sites and emphasizes the importance of geoscience discipline in solving the problem. Metasedimentary rock of Okcheon group, coal bed of Pyeongan group, Mesozoic volcanic rock. and Tertiary sedimentary and volcanic rocks are the major rock types with a high potential for acid drainage upon excavation in Korea. The acid drainage causes the acidification and heavy metal contamination of soil, surface water and groundwater, the reduction of slope stability, the corrosion of slope structure, the damage on plant growth, the damage on landscape and the deterioration of concrete and asphalt pavement. The countermeasure for acid drainage is the treatment of acid drainage and the prevention of acid drainage. The treatment of acid drainage can be classified into active and passive treatments depending on the degree of natural process in the treatment. Removal of oxidants, reduction of oxidant generation and encapsulation of sulfide are employed for the prevention of acid drainage generation.

• Korean Journal of Plant Taxonomy
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• v.51 no.3
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• pp.250-293
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• 2021

Limestone areas are sedimentary rock outcrops consisting of calcium carbonate created several hundreds of millions of years ago by calcium-secreting marine organisms and subsequently lifted above sea level by tectonic movement. Limestone areas support very high levels of endemic species of plants and are recognized as biodiversity areas with much biological information. The purpose of this study is to devise a strategy for the comprehensive conservation of the vegetation of limestone areas through analyses of the floristics and plant species compositions in ten limestone areas on the Korean Peninsula. The results of 153 field surveys from April of 2010 to October of 2016 identified 1,202 taxa in total, representing 1,096 species, 18 subspecies, 84 varieties, 2 forms, and 2 hybrids in 530 genera and 133 families. Among them, 55 taxa were endemic plants to Korea, and 38 taxa were red data plants. The floristic target plants amounted to 102 taxa, specifically 27 taxa of grade V and 75 taxa of grade IV. In all, 121 alien plants were recorded in the investigated area. Calciphilous plants amounted to 102 taxa, specifically 14 taxa of calciphilous indicator plants, 30 taxa of superlative most calciphilous plants, and 58 taxa of comparative more calciphilous plants. A cluster analysis showed a high degree of similarity between sites that are geographically adjacent with similar habitat environments. Limestone areas also supported groups distinct from those in non-limestone areas, demonstrating the specificity of limestone flora. Plant geography approaches therefore appear to be crucial to gain a better understanding of the level of biodiversity in limestone areas, not only at the interspecific but also at the intraspecific level. These results highlight the importance of protecting limestone habitats to preserve not only their interspecific but also the intraspecific diversity, which is highly threatened.

• Economic and Environmental Geology
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• v.52 no.3
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• pp.223-230
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• 2019

The calcination of oyster shells have been studied as the possible substitute for the limestone used as an absorbent of $SO_2$ gas. However, since pure shells can not be used in calcination process, some impurities are contained and the changes in the characteristics of the calcination products are expected. In this study, the surface characteristics of the calcination products are investigated by mineralogical analysis according to the contents of NaCl, which can be derived from sea water, and sediments on the surface of the shell as impurities. The marine sediments on the shells were mainly composed of quartz, albite, calcite, small amounts of amphibole and clay minerals such as ilite, chlorite and smectite. After calcination of oyster shells mixed with 0.2-4.0 wt% sediments at $900^{\circ}C$ for 2 hours, regardless of the dehydration, dehydroxylation, and phase change of these minerals at the lower temperature than this experiment, no noticeable changes were observed on the specific surface area of the calcined product. However, when mixed with 0.1 to 2.0 wt% NaCl, the specific surface area generally increases as compared with the shell sample before calcination. The specific surface area increases with increasing amount of salt, and then decreases again. This is closely related to the changes of surface morphology. As the amount of NaCl increases, the morphology of the surface is similar to that of gel. It changes into a slightly angular, smaller particle and again looks like gel with increasing amount of NaCl. Our results show that NaCl affects morphological changes probably caused by melting of some oyster shells, but may have different effects on the specific surface area of calcination product depending on the NaCl contents.