• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.66-73
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• 2001

Yangsan fault in the southeastern part of Korean peninsula has been locally reactivated along a prexisted fault during the late Pleistocene time. Geomorphological evidence of the reactivation is revealed at the northern segment(Yugye-ri, Tosung-ri areas) of the Yangsan fault. The reactivation is distinctively characterized by fault gouge and fracture zone with high frequency in the Yugye-ri area. Obique slip separation of the area is about three meters of the middle terrace. The cumulative vertical displacement is recognized after the formation of the middle terrace. Age of the reactivated faulting is constrained to during the formation of dissected valley deposits. Average vertical slip based on paleo-event is inferred to about 0.5-0.7 meter in this area.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.74-80
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• 2001

The estimation of recurrence interval for fault activity and earthquake is an important input parameter for seismic hazard assessment. In this study, the methods of recurrences interval estimation were reviewed and tentative calculation was performed for age dating data which have uncertainty. Age dating data come from previous studies of Ulsan fault system which is a well developed lineament in the southeastern part of korean Peninsula. Age dating for fault gouges, parent rocks, Quaternary sediments and veins were carried out by several researchers through various methods. Recurrence interval for fault activity was estimated on the basis of the age dating data of minor fault gouge and sediments during past 3Ma. The estimated recurrence interval was about 430-500 ka. Exact estimation of recurrence interval for fault activity need to compile more geological data and fault characteristics such as fault length, amount of displacement, slip rate and accurate fault movement age. In the future, the methods and results of fault recurrence interval estimation should be considered for establishing the criteria for domestic active fault definition.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.349-352
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• 2001

Shape separation method - a separation process which utilizes the fact that particles of different shape behave differently in force fields- is regarded as an useful measure for recycling, mineral processing, upgrading powdered material and so on. In this study, a trial was given to shape separation method using fluid field to recover pure diatom skeleton - which is thought to have many uses in itself and potential for various applications -from low grade diatomaceous earth of southeastern part of the Korean Peninsula. The striking difference of shape between diatom skeleton and other minerals like clay and quartz made it natural to choose shape separation method. Considering the size of particles to be separated, among many possible methods of shape separation, hydrodynamic field using hydrocyclone was adopted. And it resulted in recovery of pure diatom skeleton with high purity

• Journal of the Earthquake Engineering Society of Korea
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• v.4 no.3
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• pp.99-105
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• 2000

한반도 동남부 지역에서 발생하고 관찰된 약진 또는 중진의 자료를 이영하여 이 지역의 Q값과 지진원의 특성인 모서리 주파수 (fc), 응력강하량(Δ$\delta$) 및 모멘크규모 (Mw)를 산정하였다. 가속도 스펙트럼의 경사와 관련된 x의 통계학적 분포로부터 추정한 Q의 95% 신뢰범위는 1656~2454 이다. 1998년 1월 18일 울산 앞바다 지진과 1997년 6월 26일 경주지진의 지진원 요소를 구한 결과 fc 는 각각 4.22Hz , 2.94Hz, Δ$\delta$는 각각 106.8 bar, 106.2 bar, Mw는 각각 3.9, 4.0으로 추정되었다. 제한된 자료수로 인하여 이들의 통계학적 성질을 충분히 규명하지는 못하였지만 다른 연구자들의 기존결과와 유사한 값을 보인다. 본 연구의 결과는 강진동 모사에 직접 이용이 가능하며, 이 지역에 위치한 원자력 발전소 내진 안전성 검토에도 이용될 수 있다.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.30-37
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• 2003

Lineaments along the Yangsan and Ulsan fault systems were extracted through aerial photograph interpretation in the southeastern part of Korean Peninsula. Lineaments can be classified into five ranks on the basis of certainty and divided by curvatures. Mean strikes of all lineament by aerial photograph interpretation is dominant in NS ~N05$^{\circ}$E direction along the Ulsan fault system and Nl5-20$^{\circ}$E direction along the Yangsan fault system respectively. The curvature of lineament around Yangsan Fault is different from around the Ulsan Fault system, the former shows that straight lineament is dominant but the latter curved lineaments are dominant. It indicates that the Quaternary faults around Ulsan Fault would be appeared as reverse fault.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.33-40
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• 2006

Since early 1990's, several Quaternary faults have been found in the southeastern part of the Korean peninsula with reference to fault activity. Because some of these faults could be considered a capable fault, it is a very delicate matter, which need to be deal with carefully in assessing the seismic hazard. In determining whether or not a faults are capable, because of the low rate of seismicity and insufficient relationship between instrumental macro-seismicity and fault, there has been considerable debate among geologists and geophysicists in Korea. In this study, we discuss the criteria and probabilistic approaches that are used to assess whether or not a fault is seismogenic. And, we preliminarily also suggest the probability of fault activity from the spatial association between faults and earthquake epicenters, fault slip and tectonic stress, and geological evidence for multiple episodes of reactivation.

• Economic and Environmental Geology
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• v.16 no.1
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• pp.11-18
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• 1983

Gyeongsang Basin in the southeastern part of the Korean peninsular is characterized by many fault systems. To decipher the geotectonical evolution of the Korean peninsular and marginal basins in her adjacent areas it is prerequisite to understand the spatial distribution pattern and mutual relationships of these fault systems. Because of difficulties in finding any criterion to recognize the faults in field, their extension and mutual relationships in ages are not very clear yet. As an attempt to find geophysical criteria to recognize the fault, geoelectrical resistivity survey was carried out in this study. With the Wenner configuration four resistivity soundings and twenty seven resistivity profilings were done. The electrode distance used was up to 50m. From the results of the resistivity soundings and boring data of earlier groundwater investigations the depth of alluvial and weathered zone was established to be at most 20m in the study area. In the resistivity profiling low resistivity anomaly zones are detected on every traverse, which are interpreted as caused by fractures, fault clays and mylonites in the fault zone. The width of the fault zone amounts to 0.3-1km. By correlating and connecting the negative anomaly zones from traverse to traverse one can determine the trend of th of the faultzone and therefore that of fault itself. The recognized fault trend in this way was $N15^{\circ}-20^{\circ}E$ and this coincides with the direction of the inferred fault line from earlier geological surface mapping. With the help of this characteristical negative anomaly the existance of another $N80^{\circ}W$ trending fault was estabished. This study has shown that geoelectrical resistivity survey can be applied successfully to the problem of tracing fault line insofar as a fault zone has been developed along fault line.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.4
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• pp.345-352
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• 2010

The objective of this paper is to explore the short-term variability of water temperature and chlorophyll a (Chl-a) derived from in-situ and satellite data (NOAA, Sea WiFS and QuikScat) in the upwelling region of the southeastern part of Korean Peninsula in June and August, 2007. Particularly we focused on the spatial variability of sea surface temperature(SST) and Chl-a in the East Korean Warm Current region. In the results of the in-situ data, the peaks of Chl-a in june was shown at a depth of 50m The peaks of Chl-a in August was shown at a depth of 10m at the stations 4 and 5 near the land, and a depth of 30m at the other stations. The Chl-a concentrations in August were also lower than those in june except for station 5. As a result, the peaks of Chl-a in August occurred at a depth of 20~40 m shallower than those of Chl-a in june. This indicates that the nutrient-rich water within the mixed layer depth may be immediately supplied by the coastal upwelling, which is due to the southerly component of wind. The relationship between SST and Chl-a showed a negative correlation, and the high concentration of Chl-a occurred in the cold water area. The southerly wind and the East Korean Warm Current influenced a remarkable offshore movement of the cold water and Chl-a near the coastal area.

• Journal of Environmental Science International
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• v.14 no.11
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• pp.1015-1026
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• 2005

The southeastern coastal area of the Korean peninsula has a complex terrain including an irregular coastline and moderately high mountains. This implies that mesoscale circulations such as mountain-valley breeze and land-sea breeze can play an important role in wind field and ocean forcing. In this study, to improve the accuracy of complex coastal rind field(surface wind and sea surface wind), we carried out the sensitivity experiments based on PBL schemes in PSU/NCAR Mesoscale Model (MM5), which is being used in the operational system at Korea Meteorological Administration. Four widely used PBL parameterization schemes in sensitivity experiments were chosen: Medium-Range Forecast (MRF), High-resolution Blackadar, Eta, and Gayno-Seaman scheme. Thereafter, case(2004. 8. 26 - 8. 27) of weak-gradient flows was simulated, and the time series and the vertical profiles of the simulated wind speed and wind direction were compared with those of hourly surface observations (AWS, BUOY) and QuikSCAT data. In the simulated results, the strength of rind speed of all schemes was overestimated in complex coastal regions, while that of about four different schemes was underestimated in islands and over the sea. Sea surface wind using the Eta scheme showed the highest wind speed over the sea and its distribution was similar to the observational data. Horizontal distribution of the simulated wind direction was very similar to that of real observational data in case of all schemes. Simulated and observed vertical distribution of wind field was also similar under boundary layer(about 1 km), however the simulated wind speed was underestimated in upper layer.

• Journal of The Geomorphological Association of Korea
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• v.24 no.3
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• pp.1-11
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• 2017

The pollen analysis on the deposits of the lower marine terrace I of the estimated paleoshoreline height of 18m was performed in order to estimate the formation age of this terrace developed at the Sanha-dong coast, Ulsan, southeastern coast of the Korean peninsula. The pollen assemblage of the peat layer of SH-1 pollen zone (Quercus-Ulmus/Zelkova zone), lying directly on the marine rounded pebble layer of this terrace, shows that the climatic environment of the deposition period of SH-1 pollen zone was almost similar to that of the Postglacial climatic optimum period, but slightly cooler than that of the late warm stage of Last Interglacial(MIS 5a) in the eastern coast of Korea. This heightens the possibility that the deposition period of the marine rounded pebble layer which was covered by the above SH-1 peat layer is the MIS 5e which has been estimated by a previous study of the sedimentary facies of this terrace deposits (Choi, 2016). The pollen assemblage of SH-2 pollen zone (Pinus-Quercus zone) shows that the climate of this period was almost similar to that of the late Postglacial, but slightly cooler than that of the period of SH-1 pollen zone. This means that the climate around the Sanha-dong was still warmer in the deposition period of the peat layer of SH-2 pollen zone. Thus, the peat layer of SH-2 pollen zone was considered to have been deposited during the period from the early regression stage of the MIS 5d which is the estimated final stage in the deposition period of the above peat layer of SH-1 pollen zone to any stage in which the warmer environment of MIS 5 has still lasted. The humic silt layer of SH-3 pollen zone (Pinus-Ulmus/Zelkova-Abies zone) is assumed to have been deposited during the interstadial of the Last Glacial (MIS 3).