• The Journal of the Petrological Society of Korea
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• v.28 no.4
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• pp.347-357
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• 2019

The main fault zone of the Yangsan Fault, located in the southeastern part of the Korean peninsula, is newly found at the Cheonjin-ri, Dudong-myeon, Ulju-gun, Ulsan, Korea. About 100 wide fault zone exposed along the Guryangcheon stream strikes N-S and dips over 70° toward east. The main fault zone is composed of N-S-striking gouge and breccia layers and enclosed lenses. Striations on the subvertical fault surfaces mainly indicate dextral slip, but moderate-angle minor reverse faults showing top-tothe-west shearing transect the foliated high-angle gouge and breccia layers. These indicate that the dextral slip along the fault, which is interpreted as the main movement of the fault, was followed by reverse slip. The fault zone is composed of N-S-striking gouge layers and enclosed, fractured lenses. Locally distributed NE-SW- to E-W-striking fault gouge layers with fractured lenses show asymmetric folds, indicating progressive dextral movement. Therefore, the exposed fault zone has a high internal complexity due to the combined effects of NNE-SSW-trending dextral shearing and E-W-trending shortening by compression. In addition, around main boundary fault between the western volcanic rocks and eastern sedimentary rocks offsets the overlying Quaternary fluvial conglomerate. This is a good example that understanding of internal structures of main fault zone (or fault core), such as the Yangsan Fault, plays an important role to study the Quaternary activity and to find the active fault.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.598-610
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• 2022

Avoiding a fault zone would be a best practice for safety in underground construction, which is only sometimes possible because of many restrictions and other field conditions. For instance, there is an ongoing conception of Korea-Japan subsea tunnels that inevitably cross a massive fault system in the Korea Strait. Therefore it was deemed necessary to find an efficient way of predicting the likely behaviour of underground structures under fault slip. This paper presents the findings from simple numerical analysis for investigating the stress induced at a normal fault with a dip of 45 degrees. We used a boundary element software that assumed constant displacement discontinuity, which allowed the displacement to be estimated separately at both the fault's hangingwall and footwall sides. The results suggested that a principal stress rotation of 45 degrees occurred at the edges of the fault during the slip, which was in agreement with the phenomenon for fault plane suggested in the body of literature. A simple numerical procedure presented in this paper could be adopted to investigate other fault-related issues associated with underground structure construction.

• Proceedings of the Speleological Society Conference
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• 1994.11a
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• pp.80-81
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• 1994

카르스트는 특이한 수문학적 용식지형이며, 암석의 높은 용식성으로 인해 발달된 암석의 공극(1차적 삼투)과 암석의 구조적 변형인 절리면, 균렬면, 단층면, 층리면 등(2차적 삼투)의 확장으로 인하여 발생되어진 경관을 총칭한 것이다. 암석의 용식성만으로 카르스트가 형성된다는 것을 실명하기는 쉽지가 않다. 왜냐면 암석의 구조적인 특성이 중요한 인자가 되기 때문이다.(중략)

• The Korean Journal of Quaternary Research
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• v.18 no.1 s.22
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• pp.21-30
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• 2004

The Ilgwang Fault is NNE-striking, elongated 40 Km between Ulsan and Haeundae-ku, Busan in southeastern part of the Korean Peninsula. This paper si mainly concerned about the ages of the fault activities especially in the Quaternary, inferred from classification of geomorphic surfaces and trench excavation for the construction of Singori nuclear power plant. The geomorphic surfaces are classified into Beach and the Alluvial plain, the 10 m a.s.l. Marine terrace(MIS 5a), the 20 m a.s.l. Marine terrace(MIS 5e), the Reworked surface of 45 m a.s.l. Marine terrace(MIS 7 or 9) and the Low relief erosional surface. The Low relief erosional surface is distributed coastal side, the Reworked surface of 45m a.s.l. Marine terrace inland side by the Ilgwang Fault Line as the boundary line. But the former is above 10 m higher in relative height than the latter. The 20 m a.s.l. Marine terrace on the elongation line of the Ilgwang Fault reveals no dislocation. A site was trenched on the straight contact line with $N30^{\circ}E$-striking between the 10 m a.s.l. Marine terrace and the 20 m a.s.l. Marine terrace. Fault line or dislocation was not observable in the trench excavation. Accordingly, the straight contact line is inferred as the ancient shore line of the 10 m a.s.l. Marine terrace. The Ages of the Fault activities are inferred after the formation of the Ichonri formation - before the formation of the 45 m a.s.l. Marine terrace(220 Ka. y. B.P. or 320. Ka. y. B.P.). The Low relief erosional surface was an island above the sea-level during the formation of the 45 m a.s.l. marine terrace in the paleogeography.

• Journal of the Korean Geophysical Society
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• v.2 no.4
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• pp.235-240
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• 1999

From the seismic network data of the Korea Institute of Geology, Mining & Materials during 1995-1996, we derived a composite fault-plane solution of the microearthquakes occurred in the Yangsan fault area. The composite fault-plane solution of nine events shows the orientation of fault 15 ± 3°in strike, 60 ± 8°in dip and 140°in rake or 128 ± 3°in strike, 56 ± 8°in dip and 37°in rake. The compressional axis of the stress field trends ENE to WSW, and this field suggests strike-slip motion with thrust component. The result is consistent with the 1996 Yeong-weol event and the stress field in and around the Korean Peninsula, previously reported.

• Tunnel and Underground Space
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• v.19 no.2
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• pp.132-145
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• 2009

Faults in rock mass have strong influences on the behaviors of rock structure such as rock slope, tunnel and underground space. Thus, it is very important to analyse for the characteristics of fault rocks in design for tunnel. But, due to the limitation of geotechnical investigation in design stages, tunnel engineers have to carry out the face mapping and additional geological survey during tunnel excavation to find the distribution of faults and the engineering properties of faults for support and reinforcement design of tunnel. In this study, various geological survey and field tests were carried out to analyse the characteristics of the large thrust fault zone through the large sectional tunnel is constructed in mica-schist region. Also, the distribution of structural geology, the shape of thrust faults and the mechanical properties of fault rock were studied for the reasonable design of the reinforcement and support method for the highly fractured fault zone in the large-span tunnel.

• Journal of the Korean earth science society
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• v.34 no.1
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• pp.59-68
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• 2013

Focal mechanism solutions in the southwestern region of the Korean Peninsula ($34^{\circ}N-36^{\circ}N$, $126^{\circ}E-128^{\circ}E$) were obtained from the analysis of the recent 22 earthquakes ($M{\geq}2.0$) occurred from January, 2005 to March, 2011. The spatial differences between the epicenters recalculated by this study and those by KMA (Korea Meteorological Administration) and KIGAM (Korea Institute of Geoscience and Mineral Resources) are less than $0.05^{\circ}$, indicating a small deviation. However, they become a little bit larger in the coastal area due to a biased arrangement of seismic stations. Redetermined depths of hypocenters show a difference less than 12.7 km by comparison with the depth data announced by KIGAM. Most epicenters in inland area are located closely to the lineaments. Fault plane solutions were obtained from the analysis of P and SH wave polarities, and SH/P amplitude ratios. They show strike-slip faulting or strike-slip faulting with reverse components dominantly. The P-axes trends are mainly ENE-WSW or E-W directions. The direction of fault plane and auxiliary plane with 'NNE-SSW and WNW-ESE' or 'NE-SW and NW-SE' are dominant and almost parallel to the general trends of lineaments in the study area.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.213-227
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• 2002

절토사면의 붕괴원인은 토질 및 지질조건, 지형, 강우, 지하수 및 지표수, 사면형상, 굴착 및 발파와 같은 인위적인 조건, 사면보호공 등과 같이 다양한 영향이 있을 수 있으나 가장 많은 영향을 주는 원인으로 토질 및 지질적인 조건이라고 할 수 있다. 본 논문은 이러한 지질조건에서 붕괴가 발생될 경우의 활동면에 대한 전단강도 추정하는 방법에 있어 역해석법에 의한 활동면의 전단강도 추정을 연구하였다 연구결과 붕괴된 사면에서 화성암은 마찰각 20$^{\circ}$~30$^{\circ}$, 점착력 0~2t/$m^2$의 범위를 가지며 퇴적암에서는 마찰각 $10^{\circ}$~17$^{\circ}$, 점착력 0~2.5t/$m^2$의 범위, 변성암에서는 마찰각 $10^{\circ}$~40$^{\circ}$, 점착력 0~4.0t/$m^2$의 범위가 우세한 것으로 나타났다. 그리고 지질구별 구분에 의하면, 절리에 의해 붕괴가 발생된 경우에는 마찰각 30$^{\circ}$~40$^{\circ}$, 점착력 0~3.5t/$m^2$, 엽리면은 마찰각 30$^{\circ}$~35$^{\circ}$, 점착력 0.5~3.0t/$m^2$, 단층면은 마찰각 11$^{\circ}$~38$^{\circ}$, 점착력 0~3.0t/$m^2$, 층리면은 마찰각 $10^{\circ}$~17$^{\circ}$, 점착력 0~2.5t/$m^2$ 정도의 범위를 갖는 것으로 나타났다.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.713-727
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• 2009

절토비탈면의 붕괴는 주로 지질구조 적으로 취약한 구간에서 강우, 지진, 발파진동, 굴착 등의 외적인 요인이 작용하였을 때 비탈면의 붕괴가 수반되는 경우가 많으며 내적인 요인으로 작용하는 지질구조는 구조선의 종류에 따라 붕괴규모나 붕괴양상에서 상당한 차이를 보이는 특성을 보인다. 특히, 비탈면 붕괴는 단층이나 점토가 충전된 구조선에서 문제가 많이 발생되고 방향성이 뚜렷한 엽리 및 절리에서 붕괴가 빈번한 실정이다. 단층은 일반적으로 모든 암종에서 나타나는 지질구조이나 특히, 변성암중 편마암에서 붕괴빈도가 빈번하게 발생되고 점토층이 수반되는 경우에 심하다. 본 논문은 공사당시 비교적 규모가 크게 붕괴가 발생된 붕적층 절토 비탈면과 단층파쇄대 및 암질불량의 비탈면의 붕괴사례의 안정검토 사례를 소개하고자 한다.

• Economic and Environmental Geology
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• v.52 no.3
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• pp.251-258
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• 2019

During the detailed geological survey around the southern Yangsan Fault, we newly found a Quaternary fault outcrop, which cuts unconsolidated sediments. The fault named the Sinwoo site, located in the Sinwoo pasture, Miho-ri, Duseo-myeon, Ulsan metropolitan city, is the first discovered Quaternary fault near the western part of the south Yangsan Fault. In this study, we provide information on characteristics of fault geometry and unconsolidated sediment at Sinwoo site based on the analysis data of topography, drainage, and lineament around the study site. The fault site is situated at pediment slope, but fan-shaped middle terrace, as well as thick sediment exposed at low terrace, indicates that the unconsolidated sediments have been deposited in the alluvial fan environment. The drainage develops to the third-order drainage system, and the first and the second drainage system meet at right angles to each other and form a radial drainage pattern. In addition, the NE-SW direction lineaments can be identified on the basis of the curvature of the river and the step of the topographic relief, running over the Sinwoo site. The fault of $N30-35^{\circ}E/79-82^{\circ}SE$ shows ~ 5.8 m apparent vertical offset and dominantly reverse-slip sense based on slickenline, rotation of pebbles, and drag folding at footwall. However, some discontinuous sediments observed in the footwall are interpreted as fissure-filling materials due to the strike-slip movement. Now, we are under multidisciplinary investigations of additional field survey and age dating in order to determine the evolution of Sinwoo site fault during the Quaternary.