• Journal of the Korean Geophysical Society
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• v.2 no.1
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• pp.9-26
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• 1999

The Ulleung Basin (Tsushima Basin) in the southwestern East Sea (Japan Sea) is floored by a crust whose affinity is not known whether oceanic or thinned continental. This ambiguity resulted in unconstrained mechanisms of basin evolution. The present work attempts to define the nature of the crust of the Ulleung Basin and its tectonic evolution using seismic wide-angle reflection and refraction data recorded on ocean bottom seismometers (OBSs). Although the thickness of (10 km) of the crust is greater than typical oceanic crust, tau-p analysis of OBS data and forward modeling by 2-D ray tracing suggest that it is oceanic in character: (1) the crust consists of laterally consistent upper and lower layers that are typical of oceanic layers 2 and 3 in seismic velocity and gradient distribution and (2) layer 2C, the transition between layer 2 and layer 3 in oceanic crust, is manifested by a continuous velocity increase from 5.7 to 6.3 km/s over the thickness interval of about 1 km between the upper and lower layers. Therefore it is not likely that the Ulleung Basin was formed by the crustal extension of the southwestern Japan Arc where crustal structure is typically continental. Instead, the thickness of the crust and its velocity structure suggest that the Ulleung Basin was formed by seafloor spreading in a region of hotter than normal mantle surrounding a distant mantle plume, not directly above the core of the plume. It seems that the mantle plume was located in northeast China. This suggestion is consistent with geochemical data that indicate the influence of a mantle plume on the production of volcanic rocks in and around the Ulleung Basin. Thus we propose that the opening models of the southwestern East Sea should incorporate seafloor spreading and the influence of a mantle plume rather than the extension of the crust of the Japan Arc.

• Economic and Environmental Geology
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• v.56 no.3
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• pp.277-291
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• 2023

To analyze the crustal velocity structures beneath 21 broadband seismic stations in Gangwon Province, South Korea, we first applied the H-κ stacking method to 139 teleseismic event data (Mw ≥ 5.8 and the epicentral distance of 30° - 90°) occurring between March 18, 2019 and December 31, 2022 to estimate the Moho depths and V_p/V_s ratios beneath each station. The Moho depths and V_p/V_s ratios from the H-κ stacking method range from 24.9 to 33.2 km depth and 1.695 - 1.760, respectively, and the estimated V_p/V_s ratios were applied to the joint inversion of receiver functions and surface wave dispersion to obtain 1-D crustal velocity models beneath each station. The resulting Moho depths range from 25.9 to 33.7 km depth, similar to the results from the H-κ stacking method. Moho depth results from the both methods are generally consistent with Airy's isostasy. The 1-D crustal velocity models confirm that the existence of 2 km thick low-velocity layers with P-wave velocities of 5 km/s or less at some stations in the Taebaeksan basin, and at the stations CHNB and GAPB in northern Gangwon Province, which are located above the Cenozoic sedimentary layer. The station SH2B, although not overlying a sedimentary layer, has a low P-wave velocity near the surface, which is probably due to various factors such as weathering of the bedrock. We also observe a velocity inversion with decreasing velocity with depth at all stations within 4 - 12 km depths, and mid-crustal discontinuities possibly due to density differences in the rocks at around 10 km depth below some stations.

• Proceedings of the KSEEG Conference
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• 2003.04a
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• pp.139-142
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• 2003

지구물리학적 연구에서 있어서 가장 중요한 목적 중의 하나는 지각과 상부 맨틀의 상세한 구조를 규명하는 것이다. 3성분의 지진기록을 이용하여 관측소 하부의 지각구조를 연구하는 몇 가지 방법들이 개발되었으며, 수신함수분석(receiver function analysis)이 가장 널리 사용되고 있다 (Phinney, 1964: Burdick and Langston, 1977: Owens and Crosson, 1988). 수신함수는 원거리 지진의 P파와 관측소 하부의 Moho면에서 전환된 Ps 전환파를 이용하여 관측소 하부의 지각구조를 계산하는 것이다. (중략)

• The Journal of the Korea Contents Association
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• v.16 no.8
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• pp.48-58
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• 2016

The purpose of this study is to identify the effects of perceptions of organizational politics(i.e., POPs) and leader-member exchange(i.e., LMX) on the perceived work performance. Also, this paper investigates the moderating effect of LMX on the relationship between POPs and work performance. Particularly, this study is to expand on prior research by investigating the three-way interaction effect of LMX and self-efficacy. The summary of results based on a sample of 280 employees who were working in various organizations in KOREA is following. First, POPs were not significantly related to perceived work performance. Second, LMX was positively and significantly related to perceived work performance. Third, LMX did not moderate the negative relationship between POPs and perceived work performance. Finally, our results showed that for individuals with a high level of self-efficacy, LMX moderates the negative relationship between POPs and perceived work performance. That is, for individuals with a high level of self-efficacy, POPs were positively related to work performance under high LMX(in-group), but were negatively related to work performance under low LMX(out-group). Theoretical and practical implications of our findings as well as directions for future research are provided.

• Journal of the Korean earth science society
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• v.22 no.1
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• pp.20-29
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• 2001

P wave traveltime delays has been measured and a preliminary tomouaphic inversion has been performed using the data collected from the network deployed by Korea National University of Education in the southcentral part Korea. The maximum variation in relative traveltime residuals is almost 0.7 seconds. A large azimuthal variation in traveltime residuals is observed at the stations in the northwestern part of the study area. This might indicate the existence of lateral velocity heterogeneity beneath the study area. Although, the inverted tomographic image seems to be correlated with the tectonic boundary between Kyunggi Massif and Okcheon Belt, the confidence level is presently low. We should place on the importance of this study for finding preferable inversion parameters and predicting probable result. Better tomographic image of the study area can be obtained in the near future when the data are accumulated.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1997.11a
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• pp.183-188
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• 1997

안구의 운동은 시각 환경에서의 진행중인 정보처리와 관련된 지각적, 인지적 과정을 밀접히 반영하는 중요한 지표로서, 특히 공간 지각과의 상관은 비교적 명확히 확립되어 있다. 본 연구는 공간지각에 관여하는 안구운동의 특성을 파악하여, 공간지각을 반영하는 안구운동 지표를 개발한다는 목표 아래, 피험자가 느끼는 공간의 확장과 축소의 특성을 이중도약과제(double-step paraeigm)를 사용하여 관찰한 것이다. 이중도약과제는 도약(saccadic)안구운동의 오차를 유발시키는 실험기법으로, 두개의 시각자극을 하나씩 연속적으로 보여주되, 두번째 자극은 안구운동이 일어나는 도중에 제시하는 것으로서, 인위적으로 왜곡된 공간에 대한 피험자의 공간적응을 관찰하는데 사용되었다. 이 과제는 다시 자극의 이차도약 방향에 따라 축소감 조건과 확장감 조건으로 나뉘었고, 머리운동의 역할을 판별하기 위해 머리를 고정한 조건과 머리를 자유롭게한 조건으로 분류되었다. 그 결과 머리가 고정된 상태에서는 축소감 조건에 대한 적응이 확장감 조건에서보다 더 빨리 일어나고, 그 적응후의 시선이동의 변화량에서도 축소감 조건이 더 크게 나타났다. 또한 머리를 자유롭게 할 공간 지각의 정확성이 증가하며, 축소감과 확장감 경험속도의 차이가 약 49.2%까지 해소되었으나, 여전히 축소감의 경험이 더 잘 일어났다.

• The Journal of the Korea Contents Association
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• v.11 no.8
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• pp.1-13
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• 2011

In order to create an intelligent autonomous agent in virtual world, we need a sophisticated design for perception, recognition, judgement and behavior. We develop the perception and recognition functions for such an autonomous agent. Our perception mechanism identifies lines based on differences in color, the primitive visible data, and exploits those lines to grasp shapes and regions in the scene. We develop an inferencing algorithm that can infer the original shape from a damaged or partially hidden shape using its characteristics from the ontology in order to intelligently recognize the perceived shape. Several individually recognized 2D shapes and their spatial relations form 3D shapes and those 3D shapes in turn constitute a scene. Each 3D shape occupies its respective region, and an agent analyzes the associated objects and relevant scenes to recognize things and phenomena. We also develop a mechanism by which an agent uses this recognition function to accumulate and use her knowledge on the scene in the historical context. We implement these functions presented above against an example situation to demonstrate their sophistication and realism.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.103-107
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• 2005

In order to investigate the velocity structure of the southern part of the Korean peninsula, exploded seismic signals were recorded for 120 s along a 294-km WNW-ESE line and 150 s along a 335-km NNW-SSE line in 2002 and 2004, respectively. Velocity tomograms were derived from inverting first arrival times. One-dimensional velocity models derived by joint analyses of teleseismic receiver functions and surface wave dispersion at several stations near the profiles were uesd to build initial models. The raypaths indicate several midcrust interfaces including ones at approximate depths of 2.0 and 14.9 km with refraction velocities of approximately 6.0 and 7.1 km/s, respectively. The deepest significant interface varies in depth from 30.8 km to 36.1 km. The critically refracting velocity varies from 7.8 to 8.1 km/s along this interface which may correspond to the Moho discontinuity. The velocity tomograms show (1) existence of a low-velocity zone centered at 6-7 km depth under the Okchon fold belt, (2) extension of the Yeongdon fault down to greater than 10 km, and (3) existence of high-velocity materials under the Gyeongsan basin whose thickness is less than 4.2 km.

• Journal of the Korean Geophysical Society
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• v.8 no.1
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• pp.45-48
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• 2005

In order to investigate the velocity structure of the southern part of the Korean peninsula, exploded seismic signals were recorded for 120 s along a 294-km WNW-ESE line and 150 s along a 335-km NNW-SSE line in 2002 and 2004, respectively. Velocity tomograms were derived from inverting first arrival times. One-dimensional velocity models derived by joint analyses of teleseismic receiver functions and surface wave dispersion at several stations near the profiles were uesd to build initial models. The raypaths indicate several midcrust interfaces including ones at approximate depths of 2.0 and 14.9 km with refraction velocities of approximately 6.0 and 7.1 km/s, respectively. The deepest significant interface varies in depth from 30.8 km to 36.1 km. The critically refracting velocity varies from 7.8 to 8.1 km/s along this interface which may correspond to the Moho discontinuity. The velocity tomograms show (1) existence of a low-velocity zone centered at 6-7 km depth under the Okchon fold belt, (2) extension of the Yeongdon fault down to greater than 10 km, and (3) existence of high-velocity materials under the Gyeongsan basin whose thickness is less than 4.2 km.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.29-36
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• 2005

The crustal structure of Korean Peninsula is investigated by analyzing phase velocity dispersion data of Rayleigh wave. Earthquakes recorded by three component seismographs during 1999 - 2004 in South Korea are used in this study. The fundamental mode signals of Rayleigh waves are obtained from vertical components of seismograms by multiple filter technique method and phase match filter method. Velocity dispersion curves of surface waves for 14 propagation paths on the great circle are computed from the fundamental mode signals on the great circle path by two-station method. Treating the shear velocity of each layer as an independent parameter, phase velocities of Rayleigh wave are inverted. The result models are regarded as average structure for surface wave propagation paths respectively. All the results can be explained by an earth model of the Korean Peninsula comprising crust of shear-wave velocity increasing from 2.8 to 3.25 km/sec from top to 33 km depth and uppermost mantle of shear-wave velocity between 4.55 and 4.67 km/sec.