• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.451-458
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• 2008

The near-fault ground motion (NFGM) is characterized by a single long period velocity pulse of large magnitude. NFGM's have been observed in recent strong earthquakes, Izmit Turkey (1999), Kobe Japan (1995), Northridge USA (1994), etc. These strong earthquakes have caused considerable damage to infrastructures because the epicenter was close to the urban area, called as NFGM. Extensive research for the near-fault ground motion (NFGM) have been carried out in strong seismic region, but limited research have been done for NFGM in low or moderate seismic regions because of very few records. The purpose of this study is to investigate and analyze the effect of near-fault ground motions on reinforced concrete (RC) bridge piers with lap-spliced longitudinal reinforcing steels. The seismic performance of four RC bridge piers under near-fault ground motions was investigated on the shake table. In addition, a RC bridge pier is subjected to pseudo-dynamic loadings. Test results showed that large residual displacements were observed in RC bridge piers under NFGM. RC specimens on the shake table failed at relatively low displacement ductility, compared with the displacement ductility of RC bridge pier subjected to pseudo-dynamic loadings.

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.645-660
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• 2018

In the southeastern part of the Korean Peninsula, huge fault valleys, including the Yangsan and Ulsan faults, are recognized. These NNE-SSW trending lineaments are called as a whole Yangsan Fault System. However, this fault system is relatively poorly studied except the Yangsan and Ulsan faults. This study deduced the paleostress history based on the mutual cross-cutting relationships between geologic structures developed in the granite body near the Ilgwang fault, which is compared with previous studies. In the study area, four lineaments parallel to the Ilgwang fault are recognized, and three of them show evidences of faulting. In each lineament, both slip-senses of left-lateral and right-lateral are recognized. It indicates that these faults consistently underwent multiple deformations of inversion along the faults. The inferred paleostress directions based on the mutual cross-cutting relationships of the geological structures are as follows: 1) Tensile fractures developed in the late Cretaceous under the ENE-WSW direction of compressive stress, 2) NW-SE trending maximum horizontal principal stress generated conjugate strike-slip faults, and 3) selective reactivations of some structures were derived under the compression by the NE-SW trending principal stress.

• Economic and Environmental Geology
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• v.42 no.1
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• pp.9-25
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• 2009

The Northwestern Okcheon Metamorphic Belt in the Chungju area consists of the Munjuri Formation, the Daehyangsan Quartzite, the Hyangsanri Dolomite, and the Gyemyeongsan Formation, but the stratigraphy is still controversial. For a stratigraphic study, detailed stratigraphic sections were measured in two locations and mapping was carried out in the study area. The Munjuri Formation and the Daehyangsan Quartzite changed gradually in north and south section, but bedding parallel faults have developed in the boundary between two formations. The Daehyangsan Quartzite and the Hyangsanri Dolomite are conformable. Fault have developed in boundary between the Hyangsanri Dolomite and the Gyemyeongsan Formation. As a result of mapping in the study area, folding was recognized with $41^{\circ}/280^{\circ}$ plunging axis in the north part of the study area. Therefore, the bedding-parallel faults in the boundary might have occurred resulting from a layer parallel slip during the folding as well as the thrust. These results from this study and previous studies indicate that bedding-parallel faults in boundary between the Munjuri Formation and the Daehyangsan Quartzite are caused by a layer parallel slip during the folding. The fault between the Hyangsanri Dolomite and the Gyemyeongsan Formation is considered as a thrust fault, thereby the uppermost Gyemyeongsan Formation is placed under the Munjuri Formation. However the Gyemyeongsan Formation and the Munjuri Formation have similar age and rock composition. Hence, the Gyemyeongsan Formation is considered as an equivalent one with the Munjuri Formation. Therefore, the stratigraphy of Northwestern Okcheon Metamorphic Belt consists of the Gyemyeongsan/ Munjuri formations, the Daehyangsan Quartzite, and the Hyangsanri Dolomite in ascending order.

• The Journal of Engineering Geology
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• v.7 no.2
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• pp.101-112
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• 1997

Gravity and electrical resistivity surveys were carried out across the Kwangju fault in the downstream area of the Jangsung Lake, to investigate the location and geometrical feature of the fault. In the resistivity survey, dipole - dipole array method was adopted for 3 survey lines of which length and electrode spacing are 500m and 25m, respectively. Resistivity data are interpreted with aid of computer program "RESIS" which is widely used in resistivity data analysis and two dimensional resistivity profiles are obtained for 3 survey lines. Two large fracture zones relevant to the Kwangju fault are identified in the resistivity profiles. The total of 80 gravity data are observed with the mean spacing of 40 m and the exact leveling is accompanied to obtain more precise gravity anomalies. The subterranean density discontinuities calculated from the inverse method are appeared at the depths of 650rn and 120m. It is considered that the deep discontinuity indicates boundary between Jurassic granites and oveflying Cretaceous tuff formation. while, the shallow discontinuity is interpreted to be a boundary between alluvial deposits and basements. The subsurface geological structure to satisfy the observed Bouguer anomaly is determined from the iterative forward method in which results from existing surface geological informations, the inverse method, and from the resistivity interpretations are employed as an iuitial model. In conclusion, Kwangju fault is appeared to be a high angle normal fault mainly formed in tension stress filed.

• 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.2 no.3
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• pp.58-67
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• 1969

Songgwang lead zinc mine is located in about 12km to the north-east of Jeonju City. Geology of the mine and its visinity is consisted of Jeonju series belonged to so-called Okcheon system, Seodaesan tuff formation, Silla series, and the quartz porphyry intruded into these formations. Jeonju series comprising 3 formations; that is, of Sadaeri, Sindong, and Girinbong. Jeonju series is generally distributed in southern part of the area, striking NNW, and diping NE $30^{\circ}$, or NW $30^{\circ}$. It is deformed to form synclinorium and anticlinorium plunging to the north with low angle. In the northern part of the area, Jeonju series was cut by Sinpeongri-fault of NEE direction near Sinpeongri. In the north side of the fault, it is overturned and shows NEE or NWW strikes and NW $60^{\circ}$ dips. At the west of Songgwangri, it is cut by 3 thrusts; the two are almost parallel each other, and the third oneis manifested by the fact that the lower black shale zone thrusted over the upper limestone. Songgwangri thrust, so named, is a post-mineral fault and its plane represents a premineral slip plane. Enrichment of are took place along the bedding plane or fissure parallel to it, as seen in adit No. 1 or No. 2 along the floor of the thrust, and along the sheared zone or the brecciated zone oblique to the plane near the thrust in crystalline limestone of Sindong formation as observed in the underground levels of inclined slope. Ore minerals are chiefly zincblende, galena, pyrrhotite, arsenopyrite, acompanied pyrite and chalcopyrite, and contain Au and Ag. In earlier stage of mineralization, the limestone was recrystalized, and sulphide minerals were enriched in the· permiable zone said above by pyrometasomatism, and in later stage the limestone was affected chloritization and sericitization. However hydrothermal replacement was weak, so that enrichment did not took place. It seems that minerallizing materials came up through the premineral slip plane and injected, and replaced the limestone in permiable zone said above with sulphide are minerals. Then Songgwangri thrust took place and, the lower black shale zone thrusted upon crystalline limestone.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.18 no.1
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• pp.19-23
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• 2000

The estimation of crustal movements along the Cam Lo fault (Quang Tri province, Vietnam) from repeated GPS data (1995-1998) is addressed in this paper. The study area is relatively small and locates at about latitude of N 16 40' 10" and longitude of E 106 58' 40" in the middle of Vietnam. The network consists of 6 points, is located in 3 tectonics units, baselines are from 3 km to 11 km. GPS observations were perforemed to the stations of our network during two campaigns in March 1995 and May 1998. Considering the relation of coordinate variation and its standard deviation based on the result, some remarks can be made: during interval from March, 1995 to May, 1998, there are movements in the investigated area, and the. vertical movements are stronger than horizontal ones. The above results will be favor in a geophysical interpretation of Cam Lo fault for geologists. This seems to be an encouraging result in studying activity of faults in Vietnam.n Vietnam.

• The Journal of Engineering Geology
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• v.8 no.1
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• pp.13-23
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• 1998

An intensity of the 1997 Kyungju earthquake(M=4.3) was estimated at three hundred locations based on the field survey and questionaires from 2200 residents. The isoseismal shows almost circular pattern which doesnot reflect some specific geological trends. However,most of the Kyeongsang basin except the southwestern part is included within the area of MM intensity V. There occurred strong shaking, numerous cracks on the wall of the houses, and movement of slate on the roofs, falling of the tiles from the monument. The isoseismal of the highest MM intensity VII, 1-3 km in width and 9 km in length, is elongated along the Yangsan fault, which is located about 1.5 km west from epicenter. The lineaments near the epicenter exhibit almost N-S and NNE directions. The lineament distribution, the pattern of damage area and the solution of fault plane suggest that the Kyongju earthquake occurred with strike-slip sense along the Yangsan fault. The calculated intensity attenuation(I) with distance(R) is as follows : $I{\;}={\;}I_o{\;}+{\;}0.3461{\;}-{\;}0.3274{\;}{\times}{\;}1nR{\;}-{\;}0.086{\;}{\times}{\;}R$.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.517-523
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• 2007

Geophysical surveys(seismic refraction, electrical resistivity, and ground penetrating radar) were performed to delineate the weathering zone associated with vadose water in Chojeong area and investigate the fault related fracture zones. On the basis of seismic velocity structures, weathering layer for the southwestern part is interpreted to be deeper than for the northeastern part. The depth to bedrock(i.e., thickness of weathered zone) from seismic refraction data attempted to be correlated with drill-core data and groundwater level. As for the investigation of geological discontinuities such as fault related fracture zone, seismic refraction, electrical resistivity, and ground penetrating data are compositely employed in terms of velocity and resistivity structures for mapping of surface boundary of the discontinuities up to shallow depth. Surface boundaries of fracture zone are well indicated in seismic velocity and electrical resistivity structures. Accurate estimation of weathered zone and fracture zone can be successfully available for mapping of attitude of vadose water layer.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.345-352
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• 2007

Two-dimensional (2D) MT surveys near the Century mine in Australia have been performed with very far remote reference in Esashi, Japan (RR_ESS) as well as Gregory Downs (RR_GREG), which are roughly 6,400 km and 80 km apart from the survey area, respectively. Good quality of MT data could be obtained by remote reference processing with RR_GREG, while the coherency of magnetic fields between field sites and RR_ESS was not sufficient to be used as remote data. Both 2D and 3D inversion of 2D profile data represented the general geological structure beneath the survey area. The main target of the survey, Termite Range Fault, appeared as a boundary between a conductive block to the north and a resistive block to the south in the reconstructed resistivity section, and is inclined slightly to the north-east direction.