• Proceedings of the KSEEG Conference
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• 2002.10a
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• pp.17-30
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• 2002

삼척-도계지역 일대에 분포하는 조선누층군의 풍촌층 석회석은 품위 및 암상에따라 상부고품위대와 하부석회암대로 분대가 가능한데, 이는 삼척-태백간을 북북동으로 흐르는 오십천을 경계로 서쪽에 분포하는 풍촌층과 비교할 때 다소간의 암상차이를 보인다. 즉, 풍촌층의 특징중에 하나인 중부백운암대가 본 역 일대에서는 백운암화가 미약하여 비교적 소폭으로 확인되며, 상부백색대 역시, 발달정도가 미약한 특징을 보인다. 시추탐사결과 확인된 삼척-도계지역의 풍촌층 상부고품위대는 일반적으로 상부백색대($\pm$15m) - 백운암대($\pm$15m) - 암회색대($\pm$50m)로 구분되는 것으로 나타났다. 각각의 품위는 상부백색대 : CaO 53.4~55.6%, 백운암대 : MgO 3.0~l8.4%, 암회색대 : CaO 50.4~54.2%로 나타나 제철용으로의 사용이 가능하나 백운암대에 대한 선별채광이 부분적으로 요망된다. 이들 석회석은 오십천대단층의 수반단층인 수조의 NNE계열 정단층들에 의해 빈번히 단절되어 있으며 일부지역에서는 EW향의 역단층에 의해 규제되기도 한다. 상기 제단층들은 석회암층을 단절시킬 뿐만아니라 단층각력, 단층점토, 암맥 등의 불순대를 수반하므로 개발에 장애요소가 되고 있다. 상부고품위대 부존표고는 지역에 따라 다소 차이가 있으나 200ML 내외에서 대부분 확인이 가능하며 지표노출 규모는 작은 편이나 $10^{\circ}$이하의 완경사로 화절층 하부에 부존되어 있어 갱도 채광에 적합한 형태를 이루고 있다.

• Proceedings of the KSEG Conference
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• 2002.04a
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• pp.163-171
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• 2002

지금까지 양산단층에 대한 운동학적 해석은 단지 지질분포 특성의 차이를 근거로 단순 우수주향이동으로 해석해왔다. 그러나 일반적으로 대규모 단층들은 단계적으로 서로 다른 운동체계에서 복합적인 발달과정을 거치면서 현재의 모습으로 보인다. 따라서 양산단층의 주변 지질구조와 운동학적 관계를 알아보기 위하여 양산단층 주변의 지질분포, 지질구조, 단층주변의 소단층들에 대한 특성을 분석하였다. 양산단층 주변 퇴적암의 층리면 자세는 양산단 층이 동일한 사건의 주향이동으로 형성된 단층예인의 특성이 아니라 서로 다른 응력축의 지배를 받았거나 서로 다른 크기의 운동을 받았음을 암시하고 있다. 또한 단층의 주향을 따라 단층대 폭의 변화를 살펴본 결과 크게 5개의 주기를 가지면서 변화되고 각각의 주기는 약 25-30 km 로 규칙적으로 나타난다. 또한 단층조선이 발달된 소단층의 분석결과들은 양산단층이 한번의 운동으로 발달한 것이 아니라 매우 복잡하고 다양한 사건들을 겪은 다중 변형의 산물임을 지시하고 있다.

• Economic and Environmental Geology
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• v.51 no.2
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• pp.149-166
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• 2018

Many large earthquakes have continuously been reported and resulted in significant human casualties and extensive damages to properties globally. The accident of Fukushima nuclear power plant in Japan was caused by a mega-tsunami, which is a secondary effect associated with the Tohoku large earthquake (M=9.0, 2011. 3. 11.). Most earthquakes occur by reactivation of pre-existing active faults. Therefore, the importance of paleoseismological study have greatly been increased. The Korean peninsula has generally been considered to be a tectonically stable region compared with neighboring countries such as Japan and Taiwan, because it is located on the margin of the Eurasian intra-continental region. However, the recent earthquakes in Gyeongju and Pohang have brought considerable insecurity on earthquake hazard. In particular, this region should be secure against earthquake, because many nuclear facilties and large industrial facilities are located in this area. However, some large earthquakes have been reported in historic documents and also several active faults have been reported in southeast Korea. This study explains the evaluation methods of geological structures on active fault, fault damage zone, the relationship between earthquake and active fault, and respect distance. This study can contribute to selection of safe locations for nuclear facilities and to earthquake hazards and disaster prevention.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.11a
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• pp.188-208
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• 2002

• Journal of the Korean earth science society
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• v.24 no.4
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• pp.361-368
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• 2003

We have investigated the electric resistivity structure of the fault zone located in the Hongseong area where a big earthquake with M 5.0 occurred in 1978. Usually, Electric and Electromagnetic methods are broadly operated in the field of engineering works since these methods are effective to understand the distribution of geological weak zones - fault or fracture zones. We have conducted the dipole-dipole array resistivity method and MT(magnetotelluric) method and interpreted the resistivity distribution of the fault zone with the aid of various inversion methods. An MT survey was performed at 18 points along a 2.9 km survey line perpendicular to the fault line and a magnetic dipole source was used to enhance the S/N ratio in the high frequency. A Electric dipole-dipole array resistivity survey with the dipole length of 50 meters was carried out perpendicular to the fault. In view of two survey results, the fault marks the boundary between two opposite resistivity structures, especially the low resistivity zone is exhibited deeply through the prospective fault line. The result that the low resistivity zone is located at the center of the fault zone corresponds with the fact that the fault zone of the Hongseong area is active. We expect these results to provide basic information about the physical properties of fault zones in Korea.

• Economic and Environmental Geology
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• v.57 no.1
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• pp.73-81
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• 2024

To estimate the tectonic displacement of the Chugaryeong Fault System (CFS), gravity surveys were conducted along the Dongducheon fault (DF) and the Wangsukcheon fault (WF). A total of 1,100 stations for the DF and WF regions have been added to the current gravity database. The results of the gravity interpretation indicate that (1) the dextral displacement of the DF is about 3,000 m, similar to the tectonic displacement (2,900-3,100 m) shown in the geological map. (2) The dextral displacement of the WF is about 3,200 m. (3) Taken together, the tectonic displacement of the CFS is estimated to be about 3,000 m on average. To investigate more accurate tectonic displacement of the CFS, further gravity surveys is planned for the Pocheon fault, Gyeonggang fault, and Inje fault.

• Tunnel and Underground Space
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• v.15 no.2 s.55
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• pp.111-118
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• 2005

The area of investigation belongs to Okchon metamorphic zone and the fault fractured zone runs parallel to the tunnel direction. It causes the independent decline of tunnel face and the slackness of the tunnel surrounding base so, after all, the severe displacement has occurred within the tunnel. Accordingly, the TSP(Tunnel Seismic Prediction) survey has been performed to investigate the extent of fault fractured zone and to analize its characteristics. Also, we have analized the behavior causes by performing the tunnel face mapping and drilling investigation, and confirmed the position and scale of geological anomaly area and front fractured zone which influences tunnel excavation and supporting. Collected data analyzed ground layer condition through 3 dimensional modeling. Several variables included in the modeling were analyzed by geostastistics. The analysis of the modeling data shows that the belt of weathering by fault fractured zone is developing on the basis of the right side of tunnel and that is decreasing to the left side. The fault fractured zone was confirmed that it has strike, $N0\~5^{\circ}E$ dip NW, and it is consisted of large-scale fractured zone including several anomalies. The severe displacement in tunnel is probably caused by asymmetrical load that n generated by the crossing of discontinuity and the rock strength imbalance of tunnel's both side by fault fractured zone, and judge that need tunnel reinforcement method of grouting etc.

• The Journal of Engineering Geology
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• v.27 no.1
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• pp.9-20
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• 2017

To date, several studies have been carried out to partially compare and analyze the resistivity values within the Yangsan fault zone through the electrical resistivity survey of the exposed fault zone. However, it is not easy to directly observe a large scaled fault like Yangsan fault that has been weathered, especially due to the weathering of the fault core. This study aimed to reveal the characteristics of location, geometry, the fault core zone as well as underground distribution of the associated fault damage zone, based on the results of electrical resistivity and micro-topographic surveys as well as field geology survey in the southern Yangsan fault zone (Eonyang area). The resistivity anomaly zones developed in the NNE to NE direction were confirmed by the electrical resistivity survey. According to the electrical resistivity, micro-topographic, and field geologic surveys, the Yangsan fault has been formed by three to five fault cores, fault damage zones and/or fractured zones.

• Tunnel and Underground Space
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• v.24 no.4
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• pp.255-274
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• 2014

The target of this study is large scale rock slope collapsed by around 7 pm on August, 2012, which is located at ${\bigcirc}{\bigcirc}$ limestone quarries of Gangneung city, Gangwondo. The slope prior to the collapse is formed as the height of about 200 m and the average inclination of $45^{\circ}$. The estimated amount of the collapse is about $1,500,000m^3$ with respect to the slope after the collapse. Geotechnical and field investigations such as boring, geophysical prospecting, surface geological survey, geological lineaments, borehole imaging, metric 3D imaging, experimental and field test, mining work by year, and daily rainfall were performed to find the cause of rock slope failure. Various analyzes using slope mass rating, stereonet projection, limit equilibrium method, continuum and non-continuum model were conducted to check of the stability of the slope. It is expected that the cause of slope failure from the results of various analysis and survey is due to the combined factors such as topography, rainfall, rock type and quality, discontinuities, geo-structural characteristics as the limestone cavity and fault zones, but the failure of slope in case of the analysis without the limestone cavity is not occurred. Safe factor of 0.66 was obtained from continuum analysis of the slope considering the limestone cavity, so the ultimate causes of slope failure is considered to be due to the influence of limestone cavity developed along fault zone.

• Journal of the Korean GEO-environmental Society
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• v.24 no.12
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• pp.53-60
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• 2023

Recently, along with the improvement of high-speed rail and road design speed, the proportion of tunnel construction work is increasing proportionally. In particular, the construction of long tunnels is rapidly increasing due to the mountainous terrain of our country. In this way, due to the trend of tunnels becoming longer, it is difficult to design and construct tunnels by avoiding fault zones. In the case of tunnel construction in mountainous areas, ground investigation is often difficult even during design due to the topographical conditions, making precise ground investigation difficult, and as a result, the upper part of the tunnel is damaged during tunnel construction. When fault zones, which are vulnerable to weathering, exist, the stability of the tunnel during excavation is directly affected by the fault zone distribution, strength characteristics, and groundwater distribution range. In particular, when a fault zone is distributed in the upper part of a tunnel, damage such as tunnel collapse and excessive displacement may occur, and in order to prevent this in advance, countermeasures must be established through analysis of similar cases. Therefore, in this study, when a large-scale fault zone exists in the upper part of a tunnel, the relationship and characteristics of damage to the tunnel structure were analyzed.