• Geophysics and Geophysical Exploration
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• v.11 no.1
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• pp.78-84
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• 2008

Recent earthquakes near nuclear power plants in Korea have triggered public concerns about possible seismicity of the Ulsan Fault Zone in the south-eastern part of the Korean peninsula. To reveal subsurface structures of this fault zone, we conducted high-resolution seismic refraction and reflection surveys, and closely spaced gravity measurements in the Dongchon River valley north of Ulsan, Korea. Here alluvium covers the north-south trending fault zone in a 1-km wide valley. Both source points and receivers were spaced at 5-m intervals for the 24-channel seismic refraction and reflection methods, along two profiles of 835 m and 415 m length. Gravity data were also measured along these profiles at 131 stations using a 10-m interval. Synergetic interpretation of seismic refraction, high-resolution seismic reflection, and gravity surveys across the valley indicates that the Ulsan Fault Zone was formed by apparent north-south strike-slip motions during the Cretaceous, and that some faults may have been reactivated by east-west compressional or transpressional stresses during the Tertiary or Quaternary.

• Geophysics and Geophysical Exploration
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• v.14 no.4
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• pp.274-281
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• 2011

We analysed ground motions form Mw 4.3 earthquake around Backryoung Island for the seismic source focal mechanism and horizontal response spectrum. Focal mechanism of the Backryoung Islands area was compared to existing principal stress orientation of the Korean Peninsula and horizontal response spectrum was also compared to those of the US NRC Regulatory Guide (1.60) and the Korean National Building Code. The ground motions of 3 stations, including vertical, radial, and tangential components for each station, were used for grid search method of moment tensor seismic source. The principal stress orientation from this study, ENE-WSW, is consistent fairly well with that of the Korean Peninsula. The horizontal response spectrum using 30 observed ground motions analysed and then were compared to both the seismic design response spectra (Reg Guide 1.60), applied to the domestic nuclear power plants, and the Korean Standard Design Response Spectrum for general structures and buildings (1997). Response spectrum of 30 horizontal ground motions were used for normalization with respect to the peak acceleration value of each ground motion. The results showed that the horizontal response spectrum revealed higher values for frequency bands above 3 Hz than Reg. Guide (1.60). The results were also compared to the Korean Standard Response Spectrum for the 3 different soil types and showed that the vertical response spectra revealed higher values for the frequency bands below 0.8 second than the Korean Standard Response Spectrum (SD soil condition). However, through the qualitative improvements and quantitative enhancement of the observed ground motions, the conservation of horizontal seismic design response spectrum should be considered more significantly for the higher frequency bands.

• 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 Korean Institute of Navigation and Port Research Conference
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• 2011.11a
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• pp.69-70
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• 2011

최근 해저지진의 활동에 따른 극한 쯔나미 파랑이 해안도시와 항만에 어마어마한 손상을 가져오고 있다. 전세계에 걸쳐 특정해역에서는 강한 정진형태의 부진동과 처오름이 관측되고 있다. 한반도에서는 그렇게 빈번한 발생을 나타내고 있지는 않으나, 과거기록을 보면 동해에서 몇 개의 중요한 발생사례도 존재한다. 본 연구에서는 특히 만이나 내수해역에서 최근 해저지진의 발생 추이를 분석하고 이에 따른 쯔나미 발생 메카니즘을 해석하여 새롭게 내수역에서의 수치모델에의 적용을 통해 공진을 통한 쯔나미 파랑의 변환을 다루어 통항선박에 대한 안정성 확보에 기초자료를 제공하고자 하였다. 내수역에서의 쯔나미 파랑에 대한 반응을 정합성 및 웨이블릿 해석으로 탁월 주기와 지속시간에 대한 분석으로 파악하였으며, 쯔나미파의 입사와 독립적인 공진모드의 도출은 쯔나미 재해의 경감을 위한 시설물 및 재난지역을 식별하는데 도움을 주고, 나아가서는 장래 재난에 대한 적절한 대비에 기여할 수 있을 것으로 본다.

• Journal of the Korean Geographical Society
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• v.47 no.3
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• pp.328-346
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• 2012

This study provides quantitative constraints on Neogene uplift in the Korean peninsula using onshore paleo-shoreline records and seismic data. The eastern margin of Northeast Asia including Korea sits in the back-arc system behind the Western Pacific Subduction Zone, a complex trench triple junction of the Philippine Sea, Pacific, and Eurasian (Amurian) plates. An analysis of seismic data in the subduction zone shows that the pattern of uplift in the peninsula mirrors the extent of deep seismicity in subducting Pacific plate beneath. Combined with previous tomographic studies it is proposed that uplift is partly driven by asthenospheric upwelling caused by a sinking slab during the Neogene. In addition, the SHmax orientations of E-W and N-S trends in the peninsula are consistent with the prevailing in-situ stress fields in the eastern Eurasian continent generated by various plate boundary forces. The uplift in Korea during the Late Neogene is attributed, in part, to lithospheric failure relating to faulting movements, thus providing a link between dynamic effects of mantle upwelling at sinking slab edge and lithospheric responses driven by plate boundary forces.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.2
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• pp.175-182
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• 2006

The efficient management for minimum losses and demage precautions of fragile region against coastal disasters such as seismic waves and seawater overflows is proceeding continually. This study is to analyze inundation trace and extract expected damage areas with historic records of tsunami using Geographic Information System. Creating a digital elevation model of the Mangsang and the Nobong region in the east coast, we marked inundation record of tsunami and forecasted the flood area with a seismic wave height between 3 m and 5 m. The inundation trace layers and the expected damage areas on the cadastral map layer were superimposed individually. Consequently, the range and lot numbers of inundation expected area were calculated and inundation areas of 5 m tsunami were increased by 2.8 times than 3 m tsunami in case of subject regions. Analyzed results are expected to use evacuation work in case of seismic waves and to predict the compensation of the damaged area. And this study is expected to use suitable countermeasure for prevention from natural disasters.

• Journal of the Korean Geophysical Society
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• v.5 no.4
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• pp.283-292
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• 2002

The Korean peninsula is located at the edge of the East Asian active margin. The seismic activity in the Korean Peninsula is relatively low compared with the neighboring countries China and Japan. According to the available Seismic information, the Korean Peninsula is not totally safe from the Earthquake disaster. Moreover, the area is surrounded by varies tectonic forces which is resulted from the relative movements of the surrounding tectonic plates "Pacific, Philippine Sea, Eurasian and South China". Nowadays South Korea has 65 GPS stations belong to 5 governmental organizations "each organization figure out its own GPS stations for different requirements" In order to minimize the seismic hazard in the Korean Peninsula a program for monitoring the recent crustal movement has been designed considering the uses of the available GPS station "some selected stations from the previously mentioned stations" and the tectonic settings in and around the Korean Peninsula. This program is composed of two main parts, the first part to monitor the crustal deformation around the Korean Peninsula with the collaboration of the surrounding countries "China and Japan" this part is composed of two phases "East Sea Phase and Yellow Sea Phase". These phases will be helpful in determining the deformation parameters in the East Sea and the Yellow Sea respectively While the Second part of this program, is designed to determine the deformation parameters id and around the main faults in the Korean Peninsula and the relative movement between the Korean Peninsula and the Cheju Island. Through out this study the needs of crustal movement center rose up to collect the data from the previously mentioned stations and Organizations in order to use such reliable data in different geodynamical application.

• Tunnel and Underground Space
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• v.19 no.6
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• pp.490-497
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• 2009

The horizontal and vertical response spectra using the observed ground motion from the recent 5 macro earthquakes were analysed and then were compared to both the seismic design response spectra(Reg Guide 1.60), applied to the domestic nuclear power plants, and the Korean Standard Design Response Spectrum for general structures and buildings(1997). 74 horizontal and 89 vertical observed ground motions, without considering soil types, were used for normalization with respect to the peak acceleration value of each ground motion. The results showed that the horizontal MPOSD(Mean Plus One Sigma Standard Deviation) response spectra revealed much higher values for the whole frequency bands above 1 Hz than Reg. Guide(1.60). For the vertical response spectra, the results showed slightly higher than just between 7 and 8 Hz frequency band. The results were also compared to the Korean Standard Response Spectrum for the 3 different soil types and showed that the horizontal MPOSD response spectra revealed much higher values for the whole periods below 2 second(0.5 Hz) than those of SE soil type. The vertical response spectra showed similar to the values of the Korean Standard Response Spectrum of SD soil type. These spectral values dependent on frequency could be related to characteristics of the domestic crustal attenuation and the effect of each site amplification. However, through the qualitative improvements and quantitative enhancement of the observed ground motions, the conservation of horizontal seismic design response spectrum should be considered more significantly for the whole frequency bands above the 1 Hz.

• Journal of Korean Society of Disaster and Security
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• v.12 no.3
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• pp.25-34
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• 2019

Modern disasters prevent accidents in advance and recover after accidents are very important. Our government's current response to these accidents is not appropriate. As for disaster management so far, it has been the center of disaster response and recovery efforts, and has been led by the government against it. The reality is that most private organizations and agencies have only subsidized government disaster management agencies. Korea is no longer a safe zone for earthquakes. Now for the establishment of effective disaster management system for earthquakes in the diagnosis is very urgent and the problems of the operational disaster management, which the problems of the nation.Policies to improve academic efforts to seek alternative proposal is also at a time when volume can be said to be very big need to mine. This study from 2016 to 2019, about the earthquake that took place between National Statistical Office, based on analysis of data to. First of all, research 1: What was the government's plan on Pohang earthquake? The results showed that the residents' evacuation of Pohang was important in the Pohang earthquake, but for the sake of students' safety, they were directly assigned to the test site to cope with the emergency situation. Therefore, the research and analysis shows that the nation should continue to think about the causes and responses of the damage at the disaster site and strive to develop technologies and methods to minimize the damage.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.481-487
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• 2020

This study examined the behavior change of river levees during an earthquake by numerical analysis. Unlike conventional research using artificial earthquake waves, earthquake analysis was performed using real earthquake waves. The behavior of a river levee before and after an earthquake was compared and analyzed quantitatively. Studies show that the river levee has a safety factor of approximately 28.5% due to an earthquake. On the other hand, the minimum standard safety factor is satisfied. Vertical effective stress has decreased by 81.8% due to excess pore-water pressure generated by the earthquake. In addition, liquefaction occurs in most of the foundation soil. An examination of the stress-displacement behavior due to the earthquake revealed a large amount of settlement in the backfill layer. Most of the foundation soil yielded. Therefore, the target river levee is quite vulnerable to earthquakes. Through the results of this study, the necessity of refreshing the seismic design standards for river levees is required. This study can be used as basic data for estimating the approximate damage level and vulnerable areas.