• The Journal of the Petrological Society of Korea
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• v.6 no.1
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• pp.45-51
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• 1997

Tectonic movements in the Mesozoic were significant events to structural evolution in East China, so far as to West Pacific area. Typical Mesozoic structures were formed and outcropped in Yanshanian mountain area in which Yanshanian movement was named. It is generally considered that the most of outcropping structures in this area were formed in Yanshanian movement. But general studies indicated recently that more than half of the folds were formed in Yanshanian movement. But general studies indicated recently that more than half of the folds were formed and most of fault were in great reverse activity during Indosinian movement in Late-Triassic epoch. The tectonic dynamics setting of Indosinian move ment is a N-S compressive stress system originated by northward movement of Sino-Korean massif and its collison with Xingan-Mongolia fold zone. A series of closed folds (nearly E-W axial trace)and some overturned folds were formed in Indosinian movement and incoaxially superposed by Yanshanian deformation, Faulting characteristcs in the area were thrust faulting caused by compressive stress in Indosinian movement, some of which appear to be positive structural inversion, and oblique-thrust caused by compressive-shear in Yanshanian movement.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.3-7
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• 2005

Focal mechanism of the real and imaginary faults in the western coast of Japan has been assumed by examining the previous studies on the seismicity, seismic gap, fault behaviors, seismic zoning, and faults. In the area of no seismic information, the focal mechanism has been assumed to have the maximum influence on the tsunami height in the eastern coast of Korea. The tsunami height in a particular point of the eastern coast of Korea can vary up to 7 orders with the variation of the strike of the fault in a particular source point of the western coast of Japan with constant magnitude. Tsunami scenario DB including tile arrival times and tsunami heights has been constructing by using the assumed focal mechanism of the western coast of Japan. Tsunami warning system will be reinforced by using this tsunami scenario DB near future.

• Journal of the Korean Geophysical Society
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• v.8 no.2
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• pp.93-96
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• 2005

Focal mechanism of the real and imaginary faults in the western coast of Japan has been assumed by examining the previous studies on the seismicity, seismic gap, fault behaviors, seismic zoning, and faults. In the area of no seismic information, the focal mechanism has been assumed to have the maximum influence on the tsunami height in the eastern coast of Korea. The tsunami height in a particular point of the eastern coast of Korea can vary up to 7 orders with the variation of the strike of the fault in a particular source point of the western coast of Japan with constant magnitude. Tsunami scenario DB including the arrival times and tsunami heights has been constructing by using the assumed focal mechanism of the western coast of Japan. Tsunami warning system will be reinforced by using this tsunami scenario DB near future.

• The Journal of the Petrological Society of Korea
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• v.27 no.1
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• pp.67-72
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• 2018

The K-Ar ages of a sericite quartz schist in the lower Jangsan Formation along the Okdong fault zone reported by Yun (1983) have attracted attention again because of their potential to constrain the depositional timing of the Jangsan Formation. The oldest age of $562{\pm}2Ma$ among three reported K-Ar ages in the schist led to the claim that the depositional period of the lowermost Jangsan Formation in the Joseon Supergroup is late Neoproterozoic. Its depositional age is important for understanding the tectonic evolution of the Korean Peninsula including the formation and evolution histories of its sedimentary basins. Thus, the reliability and geological meaning of three K-Ar ages in the original paper (Yun, 1983) were revisited in the review. Quartz grains in the analyzed sample contain a considerable amount of excess Ar, and therefore it is inappropriate to use the ages as a basis for a depositional age constraint of the Jangsan Formation. The timing of mylonitization in the schist is recalculated as ~170 Ma.

• Geophysics and Geophysical Exploration
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• v.13 no.4
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• pp.407-415
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• 2010

MT soundings were carried out in 2008, in northern Victoria, Australia, as a continuing collaboration research of 2007 between Republic of Korea, Australia, and Japan. The main purpose of this research is to investigate electrical conductivity structure and thus help understanding of tectonic structure in central Victoria, which is believed to be closely linked to mineralization and magmatic processes of this region. The survey area is located in western Lachlan Fold Belts, which is the part of Tasman Fold Belts in southeastern Australia. An MT profile of 2008 is almost parallel to the one of 2007 and approximately 50 km away. The 2D inversion result of MT data also shows that the position of conductivity discontinuity near surface are well matched with the positions of major faults, such as Avoca Fault, which is the structural boundary between Stawell and Bendigo Zones, and Heathcote Fault Zone, which marks the boundary between Bendigo and Melbourne Zones. It is also confirmed from resistivity image that internal faults in Bendigo Zone are in listric form, which is implied to be formed by structural shortening during compressional orogenic activity in Silurian.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.775-784
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• 2009

Weathered foliation could act as a critical failure plane because this type of plane tend to have low roughness and long extensions. A big constructed slope at $\bigcirc\bigcirc$ road construction site was failed due to the block movement along a fault zone which is parallel to foliation. Tectonic activity reactivated a fault zone parallel to foliation, and the fault clay within the shear zone metamorphosed retrogressively to chrolite. The failed block moved when the block weigh lost the balancing with the resisting force of the retrogressively metamorphosed chrolite. Evaluating the three dimensional distribution of the foliation was critical for establishing a plan for the stabilization of the slope. For this purpose, 10 boreholes were drilled as a lattice distribution, and the BIPS analyses are performed at each boreholes. The fractures measured in the boreholes are projected into 15 cross sections and their distributions are analysed, using Fracjection software. The projection analyse show that the strike of the foliation gets dipper towards left side of the slope. This geometry indicates that there are more failure block geometry at left side of the slope. Potential failure planes are searched using the projection method, and these information are provided for further support design.

• Economic and Environmental Geology
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• v.34 no.6
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• pp.555-571
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• 2001

The dynamic evolution of the Chugaryeong fault valley is studied by paleomagnetic works on 163 samples at 16 sites from Late Cretaceous and Quaternary volcanic rocks in the valley. Conglomerate test and stepwised thermal/alternating field demagnetization indicate that all the characteristic directions are of primary origin. Paleomagnetic pole ponsition(216.8$^{\circ}$E/7l .6$^{\circ}$N; dp=7.1$^{\circ}$, dm=10.0$^{\circ}$) for the upper par of the Jijangbong Volcanic Complex Is indistinguishable from the coeval retference pole position from the Gyeongsang Basin, which further substanciates the reliability of the Paleomagnetic data. This indicates the study area has not undergone any tectonic rotation since Late Cretaceous by uy significant reactivation of the Chugaryeong fault valley. The Quaternary pole position (134.2$^{\circ}$E/86.5$^{\circ}$N; $A_{95}$=7.1 $^{\circ}$) from the Jeongog Basalt reflects the present geocentric axial dipole field for the area, supporting the above conclusion. Unlike the upper part, paleomasnelic directions of the lower part of the Jijangbong Volcanic Complex show random distrinution between sites. We interpret that the early stage of the volcanic activity was created by sinistral strike slip motion of the Chugaryeong fault during early Late Cretaceous. The creation and evolution of the Chugaryeong fault valley emphasize the significance of the kinematic FR (folding ruler) model in east Asia.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.3
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• pp.235-258
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• 2022

We interpreted the evolutionary history of the southwestern part of the Pohang Basin, the largest Miocene basin in the southeastern part of the Korean Peninsula, based on the detailed geological mapping and analysis of the geological structures. The southwestern part of the Pohang Basin can be divided into the Bomun Domain in the west and Ocheon Domain in the east by an NNE-trending horst-in-graben. These two domains have different geometries and deformation histories. The Bomun Domain was rarely deformed after the incipient extension of the basin, whereas the Ocheon Domain is an area where continued and overlapped deformations occurred after the basin fill deposition. Therefore, the Bomun Domain provides critical information on the initial extension mode of the Pohang Basin. The subsidence of the Bomun Domain was led by the zigzag-shaped western border fault that consists of NNE-striking normal and NNW-striking dextral strike-slip fault segments. This border fault is connected to the Yeonil Tectonic Line (YTL), a regional dextral principal displacement zone and the westernmost limit of Miocene crustal deformation in SE Korea. Therefore, it is interpreted that the Pohang Basin was initially extended in WNW-ESE direction as a transtensional fault-termination basin resulting from the movement of NNE-striking normal and/or oblique-slip faults formed as right-stepover in the northern termination of the YTL activated since approximately 17-16.5 Ma. As a result, an NNE-trending asymmetric graben or half-graben exhibiting an westward deepening of basin depth was formed in the Bomun Domain. Afterward, crustal extension and deformation were migrated to the east, including the Ocheon Domain.

• Economic and Environmental Geology
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• v.45 no.5
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• pp.487-502
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• 2012

This paper is focused on mineral compositions, microstructures and distributional characters of remained grains in the fault rocks collected from a fault developed in Yongdang-ri, Yangbuk-myeon, Gyeongju City, Korea, using X-ray diffraction (XRD), optical microscope, laser grain size analysis and fractal dimension analysis methods. The exposed fault core zone is about 1.5 meter thick. On the average, the breccia zone is 1.2 meter and the gouge zone is 20cm thick, respectively. XRD results show that the breccia zone consists predominantly of rock-forming minerals including quartz and feldspar, but the gouge zone consists of abundant clay minerals such as chlorite, illite and kaolinite. Mineral vein, pyrite and altered minerals commonly observed in the fault rock support evidence of fault activity associated with hydrothermal alteration. Fractal dimensions based on box counting, image analysis and laser particle analysis suggest that mineral grains in the fault rock underwent fracturing process as well as abrasion that gave rise to diminution of grains during the fault activity. Fractal dimensions(D-values) calculated by three methods gradually increase from the breccia zone to the gouge zone which has commonly high D-values. There are no noticeable changes in D-values in the gouge zone with trend being constant. It means that the bulk-crushing process of mineral grains in the breccia zone was predominant, whereas abrasion of mineral grains in the gouge zone took place by continuous fault activity. It means that the bulk-crushing process of mineral grains in the breccia zone was predominant, whereas abrasion of mineral grains in the gouge zone took place by continuous fault activity. Mineral compositions in the fault zone and peculiar trends in grain distribution indicate that multiple fault activity had a considerable influence on the evolution of fault zones, together with hydrothermal alteration. Meanwhile, fractal dimension values(D) in the fault rock should be used with caution because there is possibility that different values are unexpectedly obtained depending on the measurement methods available even in the same sample.

• Journal of Science Education
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• v.33 no.1
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• pp.77-86
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• 2009

The purposes of this study were to develop an Earth Systems-based program for science-gifted students and to investigate the effects of field application. The developed program was composed of six activities focused on 'fault and earthquake'. Each step including exploratory step, enrichment step and application step was designed to be associated with aims for Earth Systems Education. Two instruments for experiments were produced and students' activity sheets and teacher's guide of the program were developed. The program was applied to 14 science-gifted students who were 8th grade belonging to an institute for science-gifted at an university. Data was collected from students' activity sheets, outcomes and questionnaires. The findings were as follows. First, the results of analyzing the students' activity sheets and outcomes indicated that the program was helpful in understanding the interactions among subsystems of the Earth. Secondly, the results of the survey indicated that positive responses in acquiring scientific concepts and the results revealed science-gifted students were much interested in this program. Many students perceived that the level of program was appropriate for the science-gifted students, a few students perceived that the level of contents was high.