• Economic and Environmental Geology
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• v.24 no.2
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• pp.177-186
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• 1991

Ogchon Supergroup directly contacts with Choseon Supergroup in the northern area of Worak-san, where evidences indicating thrust-fault formed during $D_2$-deformation are observed. On footwall of thrust fault, calcite veins in Gounri Formation belonging to Choson Supergroup may be deformed during thrust faulting($D_2$). Calcite veins are parallel to axial plane cleavage($S_2$) of $F_2$ fold and truncate slaty cleavage($S_1$). Therefore, we can use deformation twins in calcite grains of the veins as a marker for inferred differential stress operated upon thrust faulting. The inferred differential stresses are estimated at 190 Mpa from K, sample. The stress from K, sample close to the contact between Ogchon Supergroup and Choseon Supergroup shows a higher value than $K_2$-$K_6$ samples, probably having an important influence upon thrust faulting. The differential stress reveal again high value at $K_7$ sample, which may suggest the presence of another thrust fault.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.11b
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• pp.3-17
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• 2002

Tertiary Pohang basin distributed in south weatern part of the korean peninsula, is composed of Chunbuk formation as the basal conglomerate, Hakjon formation, Duho formation and intrusive basalt which is 15 Ma by absolute age data. The basement of the basin is represented by Cretaceous sedimentary rocks, Hakjon welded tuff and Chilpo welded tuff and rhyolite. The fault systems at the basement of the Pohang basin are consist of NNE direction fault, WNW to EW trend fault. NNE fault is not only strike-slip fault but also normal fault. n fault has sinistral strike-slip sene and the EW fault is strike-slip and normal fault. In the Tertiary basin, the fault system is represented by nm strike-slip fault, EW normal fault and NNE thrust fault. By these fault relationships and geometries, it is interpreted that NNE sinistral strike-slip fault and nomal fault have acted at Creceous times. At Tertiary tines, NNE dextralstrike-slip fault and EW normal fault has created. Progressively Tertiary Pohang basin was influenced by the trenspression to make thrust fault and fold, namely as inversion tectonics.

• Economic and Environmental Geology
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• v.28 no.1
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• pp.69-77
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• 1995

Tertiary Pohang basin distributed in south western part of the Korean peninsula, is composed of Chunbuk formation as the basal conglomerate, Hakjon formation, Duho formation and intrusive basalt having 15 Ma by absolute age data. The basement of the basin is represented to Cretaceous sedimentary rocks, Hakjon welded tuff and Chilpo welded tuff and rhyolite. The fault systems in the basement of Tertiary Pohang basin are consist of $N20^{\circ}E$ fault, $N60^{\circ}W$ and E-W trend. NNE fault is not only strike-slip but also normal dip-slip. WNW fault has sinistral strike-slip sense and the geometry of E-W fault is strike-slip and normal faults. In the basin, the fault system is represented to $N20^{\circ}E$ strike-slip, E-W normal and NNE thrust faults. By these fault relationship and geometry, it is interpreted that NNE sinistral strike-slip fault and N-S normal faults have acted at the Cretaceous basement. After Miocene NNE dextral strike-slip fault has acted and created E-W normal fault. Progressively Tertiary basin was influenced by the transpression to make thrust and fold, namely inversion tectonics.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.5
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• pp.835-842
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• 2020

This paper considers a method of reproducing abnormal and fault operation for smart monitoring of thrust bearing used in wave power generation system. In order to develop smart monitoring technology, abnormal and failure data of actual equipment are required. However, it is impossible to artificially break down the actual equipment in operation due to safety and cost. To tackle this problem, a test bed that can secure data through reproduction of a faulty operating environment should be developed. Therefore, in this study, test bed that can reproduce each situation was developed and the operation result was analysis after identifying the situation to be reproduced through the failure factor analysis of the thrust bearing.

• Economic and Environmental Geology
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• v.24 no.1
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• pp.27-41
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• 1991

Taebaeg-Hajang area, in the northern part of Taebaeg city, comprises of Paleozoic sedimentary sequences and Cretaceous intrusive and volcanoclastic rocks. The rocks in the area are affected by folding and thrusting during the Bulgugsa Orogeny. In Taebaeg area, geologic structures related with thrust movement are dominant. These structures are small scale of klippe and window, back thrust, and asymmetric folds related with blind thrust. Tear fault or compartment fault due to differential movement of thrust sheets have "en echelon" arrays. Small scale transpression effects occurred along these faults and produced the flower structure. According to strain measurement using by ooids from limestone and quartz grains from quartzite, strain ratios are very low and strain ellipsoids are apparent oblate type.

• Tunnel and Underground Space
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• v.21 no.4
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• pp.251-263
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• 2011

The geomechanical characteristics of rock and the structural geological feature of the fault should be studied and examined for the successful construction of large-span tunnel. In this case study, that is a important case for the tunnel collapse and reinforcement during the construction for the waterway tunnel at large thrust fault zone in schist, we carried out geological and geotechnical survey for make the cause and mechanism of tunnel collapse. Also, we have designed the reinforcement and re-excavation for the safe construction for collapse zone and have carried out successfully the re-excavation and finished the final concrete lining.

• The Journal of Engineering Geology
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• v.7 no.1
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• pp.81-90
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• 1997

The Korean historical 1iteratures describe that great eaathquakes with destructive damages occurred mainly in Kyongju-Ulsan areas during the period of 1 to 8 century and 16 to 17 century. It seems that the Ulsan fault system shows a little curved ttend with N-S strike in the southern part and diverges into three directions from the mid-northern lart of the fault. The dominant trends of the lineaments are NNE-SSW, NE-SW and NS directions. Trench excavation in the mid-northern part of the Ulsan fault shows thrust facies cutting slope deposit containing a compacted laminar structure whose origin may due to severe cryogenic activities of the last cold period(ahout 25OOO B.P.). Detailed observation of the facies gives some evidences related to two earthquake episodes of thrust components along the Ulsan fault system. Fault outcrop and trench study suggest that Ulsan fault seems to he one of the active fault which has reworked several times even in the late Quaternary.

• 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.

• Economic and Environmental Geology
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• v.22 no.3
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• pp.285-291
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• 1989

The Okdong Fault is situated in Okdong-Hamchang area, the central part of Korea. The area consists of Precambrian gneisses and granitoids, Paleozoic clastic and carbonate rocks, and Mesozoic clastic rocks and igneous intrusives. The Okdong Fault is situated along contact boundary between the lowermost Cambrian Basal Quartzite and Precambrian basements. Mylonites occur as narrow zone which is extended over 100km and is restricted to within 10m-30m along the Okdong Fault. The main features of mylonites are quartz mylonite derived from Cambrian Basal Quartzite and mylonitic granitoids from Precambrian granitoids. Movement sense is deduced as a sinistral strike-slip movement with evidence of rotation of sheared porphyroclasts, rotation of fragments and S/C-bands. The mylonite zone has been reactivated as fault which reveals oblique-slip movement. The fault resurges as faults which reveals normal(to the NW) and reverse(to the SE) dip-slip movement. Normal faults are dominant in the northern and southern part and reverse or thrust faults are dominant in the central part of the Okdong Fault. The thrust movement can be correlated with the Daebo Orogeny of Jurassic Period. Granites and dyke rocks intruded into Paleozoic and Precambrian rocks during Cretaceous Period.

• Economic and Environmental Geology
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• v.52 no.5
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• pp.395-407
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• 2019

The duplex system has been considered as an important slip-transfer mechanism to evaluate the evolution of orogenic belts. Duplexes are generally found in the hinterland portion of fold-thrust belts and accommodate large amounts of total shortening. Thus, understanding its geometric and kinematic evolution can give information to evaluate the evolution of the entire orogenic belt. Duplexes are recognized as closed-loop thrust traces on map view, indicating higher connectivity than imbricate fans. As originally defined, a duplex is an array of thrust horses which are surrounded by thrust faults including the floor and roof thrusts, and imbricate faults between them. Duplexes can accommodate regional layer-parallel shortening and transfer slip from a floor thrust to a roof thrust. However, an imbricate fault is not the only mean for layer-parallel shortening (LPS) and displacement transfer within duplexes. LPS cleavages and detachment folds can also play the same role. From this aspect, a duplex can be divided into three types; 1) fault duplex, 2) cleavage duplex and 3) fold duplex. Fault duplex can further be subdivided into the Boyer-type duplex, which was firstly designed duplex system in the 1980s that widely applied most of the major fold-thrust belts in the world, and connecting splay duplex, which has different time order in the emplacement of horses from those of the Boyer-type. On the contrary, the cleavage and fold duplexes are newly defined types based on some selected examples. In the Korean Peninsula, the Yeongwol area, the western part of the Taebaeksan Zone of the Okcheon Belt, gives an excellent natural laboratory to study the structural geometry and kinematics of the closed-loops by thrust fault traces in terms of a duplex system. In the previous study, the Yeongwol thrust system was interpreted by alternative duplex models; a Boyer-type hinterland-dipping duplex vs. a combination of major imbricate thrusts and their connecting splays. Although the high angled beds and thrusts as well as different stratigraphic packages within the horses of the Yeongwol duplex system may prefer the later complicate model, currently, we cannot choose one simple answer between the models because of the lack of direct field evidence and time information. Therefore, further researches on the structural field investigations and geochronological analyses in the Yeongwol and adjacent areas should be carried out to test the possibility of applying the fold and cleavage duplex models to the Yeongwol thrust system, and it will eventually provide clues to solve the enigma of formation and its evolution of the Okcheon Belt.