• Korean Journal of Mineralogy and Petrology
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• v.35 no.4
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• pp.485-505
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• 2022

On November 15, 2017, a Mw 5.4 Pohang Earthquake occurred at about 4 km hypocenter in the Heunghae area, and caused great damage to Pohang city, Korea. In the Heunghae area, which is the central part of the Pohang Basin, the Cretaceous Gyeongsang Supergroup and the Late Cretaceous to Early Paleogene Bulguksa igneous rocks as basement rocks and the Neogene Yeonil Group as the fillings of the Pohang Basin, are distributed. In this paper, structural and geological researches on the crustal deformations (folds, faults, joints) in the Pohang Basin and the coseismic ground deformations (sand volcanoes, ground cracks, pup-up structures) of Pohang Earthquake were carried out, and the deformation history of the Pohang Basin and characteristics of the coseismic ground deformations were considered. The crustal deformations were formed through at least five deformation stages before the Quaternary faulting: forming stages of the normal-slip (Gokgang fault) faults which strike (N)NE and dip at high angles, and the high-angle joints of E-W trend regionally recognized in Yeonil Group and the faults (sub)parallel to them, and the conjugate normal-slip faults (Heunghae fault and Hyeongsan fault) which strike E-W and dip at middle or low angles and the accompanying E-W folds, and the conjugate strike-slip faults dipped at high angles in which the (N)NW and E-W (NE) striking fault sets show the (reverse) sinistral and dextral strike-slips, respectively, and the conjugate reverse-slip faults in which the NNE and NNW striking fault sets dip at middle angles and the accompanying N-S folds. Sand volcanoes often exhibit linear arrangements (sub)parallel to ground cracks in the coseismic ground deformations. The N-S or (N)NE trending pop-up structures and ground cracks and E-W or (W)NW trending ground were formed by the reverse-slip movement of the earthquake source fault and the accompanying buckling folding of its hanging wall due to the maximum horizontal stress of the Pohang Earthquake source. These structural activities occurred extensively in the Heunghae area, which is at the hanging wall of the earthquake source fault, and caused enormous property damages here.

• The Journal of the Petrological Society of Korea
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• v.9 no.1
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• pp.40-50
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• 2000

This study is aimed at elucidating the source rocks of the Hayang strata in the northeastern part of the Gyeongsang Basin. Zircon morphology was analyzed for sandstones from the Iljig, Hupyeongdong, and Jeomgog formations of the Hayang Group and Precambrian gneisses and Jurassic granites. Generally, the composite zircon crystals extracted from the basement rocks and the Hayang Group sandstones show short prismatic to middle prismatic shapes. {110)={100) prism type is dominant and (101) pyramid is the average of the zircon morphology data. Zircon index@) and the shape trend characteristics clearly show that the zircon crystal forms of the Iljig and Hupyeongdong sandstones are dominantly similar to those of the biotite banded gneiss and granite gneiss of Precambrian age. Zircon morphology of the Jeomgog sandstones is dominantly similar to those of the Jurassic granites. Referring to the reported paleocurrent result, the source rocks of the Iljig and Hupyeongdong formations are mainly the Precambrian gneisses distributed in the southeastern and northeastern parts, respectively. And Jeomgog sandstones were mainly derived from Cheongsong granite at Cheongsong uplift region in the eastern part. At the time of completion of the Hupyeongdong sedimentation, the Precambrian basement rocks were severely eroded and formed low topography. During the Jeomgog period, the Jurassic granites which intruded the Precambrian basement began to crop out on the surface. The basin widely extended toward the east and the exposed Jurassic granite of Cheongsong uplift region actively supplied the sediments to the basin.

• The Korean Journal of Petroleum Geology
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• v.2 no.2 s.3
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• pp.51-57
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• 1994

Analysis of the aeromagnetic data aquired by US Navy in the year 1969 permits us to predict a new sedimentary basin, Heugsan Basin, south of the known Gunsan Basin in Block Ⅱ. The basin appears to consist of three sub-basins trending NNW-SSE. The results of our analysis provide not only an independent assessment of the Gunsan Basin, but also new important information on the tectonic origin and mechanism for the two basins as well as for the entire region. The basin forming tectonic style is interpreted as rhombochasm associated with double overstepped left-lateral wrench faults. From the magnetic evidence, a few NE-SW trending major onshore faults are extended to the study area. We also interpreted the nature of the faults to be left-lateral wrenches. This new gross structural style is consistent with the results of recent Yeongdong Basin analysis by Lee. The senses of fault movement are also supported by the paleomagnetic evidence that the Philippine Sea had experienced an 80-degree clockwise rotation since the Eocene. Based on a 2 $\frac{1}{2}$ model study the probable maximum thickness of the sediments in the Gunsan Basin is approximately 7500 meters. We believe that the new Heugsan Basin was left unidentified because a high velocity layer may be overlying the basin. Because the overall structural configuration of the Heugsan Basin appears to be favorable for hydrocarbon accumulation, a detailed airborne magnetic survey is recommended in the area in order to verify the magnetic expression of this thick basin. A detailed subsequent marine gravity survey is also recommended in order to delineate the sedimentary section and to acquire supplemental data to the magnetic method only if an overlying high velocity layer is confirmed. Otherwise a high energy source seismic survey may be more effective.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.357-360
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• 2005

Soil loss is widely recognized as a threat to farm livelihoods and ecosystem integrity worldwide. Soil loss prediction models can help address long-range land management planning under natural and agricultural conditions. Even though it is hard to find a model that considers all forms of erosion, some models were developed specifically to aid conservation planners in identifying areas where introducing soil conservation measures will have the most impact on reducing soil loss. Revised Universal Soil Loss Equation (RUSLE) computes the average annual erosion expected on hillslopes by multiplying several factors together: rainfall erosivity (R), soil erodibility (K), slope length and steepness (LS), cover management (C), and support practice (P). The value of these factors is determined from field and laboratory experiments. This study calculated soil erosion using GIS-based RUSLE model in Imha basin and examined soil erosion source area using SPOT 5 high-resolution satellite image and land cover map. As a result of analysis, dry field showed high-density soil erosion area and we could easily investigate source area using satellite image. Also we could examine the suitability of soil erosion area applying field survey method in common areas (dry field & orchard area) that are difficult to confirm soil erosion source area using satellite image.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.739-746
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• 1999

Discharge characteristics of organic materials and nutrients were estimated in the catchment area of relaimed area-Saemankeum-. Discharge load of BOD5 was high in the domestic system, while nitrogen and phosphorous were discharged mainly from the livestock system and the land . Load was so dependent on the precipitation that it increased in the rainy season, particulary in nitrogen and phosphorus. Loads from nonpoint sources in this area were higher compared with others.

• Journal of the Korean Association of Geographic Information Studies
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• v.23 no.3
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• pp.174-191
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• 2020

In this study, we analyzed the vulnerable areas of non-point source pollutants and management pollutants and management time by subwatershed curves in the Seohwacheon basin located upstream of Daecheongho. First, in order to create a load duration curve, a long-term flow model SWAT was constructed to create a flow duration curve, and the result was multiplied by the target water quality to create a load duration curve. For the target water quality, monitoring data values measured from November 2017 were used for the management of nonpoint source pollutants in Seohwacheon, and a value corresponding to 60 percentile of the measured data was set as the target water quality. At this time, the target water quality was limited to"slightly good"(II) when the calculated value exceeded"slightly good"(II) of the river living environment standard. The vulnerable areas of non-point source of pollution were selected using the excess rate exceeding the target water quality, and the excess pollutant was judged as a management substance and the management time was selected through seasonal evaluation.

• Journal of Environmental Science International
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• v.2 no.2
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• pp.153-160
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• 1993

The problem of supply and transport of sediment from a mountainous catchment is very important in explaining dynamic geomorphology and the hydrological cycle. The discharge of suspended sediment is determined by a morphological system. Human interference to environment Is also an important, not negligible factor in sediment production. Moreover, growing concern in recent years for the problems of nonpoint pollution and for the transport of contaminants through terrestrial and aquatic ecosystems has highlighted the role of sediment-associated transport in fluvial systems. This study was conducted in forested and quarried catchments in order to clarify the different discharge process and the mechanism of suspended sediment dynamics for each catchment. As a forested catchment, the Yamaguchi River catchment which drains a $3.12km^2$ area was chosen. On the other hand, the Futagami River basin which is formed by three subbasins (1.07, 1.59 and $1.78km^2$), as a quarried catchment was selected. These catchments are situated to the north and east of Mt. Tsukuba, Ibaraki, Japan. The discharge pattern of suspended sediment from the Futagami River basin is more unstable and irregular than that from forested catchment, the Yamaguchi River catchment. Under the similar rainstorm conditions, suspended sediment concentration from quarried catchment during a rainstorm event increases from 43 to 27,340 mg/l. However, in the case of the forested catchment it changes only from nearly zero to 274 mg/l. Generally, the supply source of suspended sediment is classified into two areas, the in-channel and non-channel source areas. As a result of field measurements, in the case of the forested catchment the in-channel (channel bed, channel bank and channel margin) is the main source area of suspended sediment. On the other hand, remarkable sediment source area on the Quarried catchment is the non-channel that is unvegetated ground.

• Journal of the korean society of oceanography
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• v.33 no.3
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• pp.64-70
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• 1998

Forty sediment samples from Kyeonggi Bay, Korea were analyzed for butyltins, including tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) to determine their distribution and source in this area. Total butyltin concentrations in Kyeonggi Bay sediments ranged from 0.8 to 297 ng/g dry wt. with a mean value of 38 ng/g. The highest butyltin concentration was found in the innermost site in Incheon Harbor basin. The mouth of Han River had higher butyltin levels in sediments compared to open ocean. Butyltin levels correlated well with organic carbon content of sediment, but the major factor was the distance from the source area where antifouling paints were used for vessels and marine structures. Butyltin concentrations in the study area were lower than those reported for bays in other parts of the world. Considering the high toxic potential and sediment/water partition coefficient of TBT, further studies are needed to assess its biological effect in the marine ecosystem of Kyeonggi Bay.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.403-407
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• 2001

For the water quality management of stream and lake, it is important to estimate and control nonpoint source loading to meet the water quality standard. So, integrated watershed management is required. BASINS is a multipurpose environmental analysis system for use by regional, state, and local agencies in performing watershed and water quality based studies. BASINS was developed by the USEPA to facilitate examination of environmental information, to support analysis of environmental systems and to provide a framework for examining management alternatives. BASINS contains HSPF which is one of the watershed runoff model. By using HSPF, nonpoint source loading from upper stream watershed was estimated. As a result, the simulated runoff was in a good agreement with the observed data and indicated reasonable applicability for whole watershed.

• Journal of Korean Society on Water Environment
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• v.20 no.6
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• pp.657-663
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• 2004

The aims of this study are the characterization of runoff from nonpoint source, the analysis of the pollutant loads and an establishment of a management plan for nonpoint source of Okcheon. For this purpose the basin of the stream So-okcheon was selected to the investigated. During the period from May 29 to July 21 in 2003, the water automatic sampler system has been installed in Okkagkyo and parameters such as SS, COD, TOC, TP and TN were analyzed. The pollutants of nonpoint source seem to be washed out along the stream water in the beginning of rainfall, remain in water and cause the stream pollution. The runoffs during heavy rainfall, especially, much higher concentration of SS than those during dry period. With respect to the annual loading of pollutants of the nonpoint source, the COD was 124 ton/yr, TOC 396 ton/yr, TN 1,429 ton/yr and TP 4.2 ton/yr in the year 2002. With respect to the pollutants loading of the nonpoint source, the COD was 375 ton/yr(95% of the total COD loading of 394 ton/yr), TOC 844 ton/yr(96% of the tatal TOC loading of 876 ton/yr), TN 1,985 ton/yr(96% of the total TN loading of 2,062 ton/yr) and TP 37.1 ton/yr(92% of the total TP loading of 40.3 ton/yr) in the year 2003.