• Geophysics and Geophysical Exploration
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• v.1 no.2
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• pp.110-115
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• 1998

Self-potential, VLF-EM and dipole-dipole resistivity methods have been widely used for exploration of conductive sulfide ore deposit, because of the convenience and low cost of field work and the reliability of their results. The geophysical responses for vein-type sulfide outcrop of Changkoom mine located in Bukwi-Myon, Jinan-Gun, Chollabuk-Do were investigated and compared with its drilling results. The geology around the survey area is composed of acidic volcanics and sediments of Yuchon Group. And sulfides bearing pyrite, pyrrotite, galena etc. are deposited in disseminated or vein type within acidic volcanics. Typical geophysical responses were detected from the above vein type ore body, respectively. From the shape and extent of S.P. anomaly, ore body is dipping westward and extending about 50 m. It is detected that the VLF EM response matching the outline of ore zone is considered as indication of dyke dipping westward. And also resistivity response indicating conductive dipping dyke is detected. From drilling results for outcrop and geophysical anomalies, the shape of ore body is vein type dipping about $70^{\circ}W$ and extending about 50 m.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.4
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• pp.373-386
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• 2014

This paper concerns the deformation behavior of tunnels crossing weak zone during excavation. A three dimensional finite element model was adopted in order to conduct a parametric study on the orientation of weaj zone in terms of strike and dip angle relative to the tunnel longitudinal axis. The results of the analyses were then analyzed so that the tunnel displacements in terms of the ratios between the crown settlement and springline displacement can be related to the orientation of the weak zone. The results indicate that the displacement ratios between the tunnel crown and springline tend to quantitatively change when a weak zone exists near or ahead of the tunnel suggesting that the displacement ratios can be effectively used to predict the weak zone during tunnelling. Practical implications of the findings are discussed.

• Geophysics and Geophysical Exploration
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• v.17 no.2
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• pp.58-65
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• 2014

We studied the source mechanisms of very-long-period event recorded at seismic station WIZ near White Island Volcano, New Zealand on August 4, 2012. Since seismic data at only one station were available, we conducted moment tensor inversion using three simplified models (explosion, crack, and pipe models). To constrain the moment tensor solution of seismic event, we computed synthetic data for each model to compare with observed data. Type and orientation for the best model is a crack at a depth of 1600 m with a dip of $80^{\circ}NE$ and a strike of $N80^{\circ}W$. We interpret that a deep explosion may have opened a crack for gases to escape, and the upward gas flow triggered the surface explosions four hours later as confirmed by a webcam. The interpretation based on moment tensor inversion is consistent with previous studies of geochemical data of the volcanic island.

• Journal of Wetlands Research
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• v.12 no.2
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• pp.1-12
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• 2010

This study examined geological characteristics of a wetland in Mountain Geumjeong in Busan Metropolitan City. Field survey and laboratory tests were performed to identify topographic features, geological and structural geological characteristics, rock strength along the distance from the wetland, soil profile in the wetland, and chemical property of the wetland soil. The bedrock of the wetland consists of hornblende granite. Hornblende granite and rhyolitic rock around the wetland have the joints with strikes of N-S, E-W, and NE-SW directions and with higher dips greater than $60^{\circ}$. Lower rock strength and higher weathering grades take place towards the wetlands. According to X-ray diffraction analysis of wetland soil samples, kaolinite, montmorillonite, and gibbsite appear which demonstrate weathered products of feldspars in the hornblende granite. The soil profile in the wetland comprises O, A, B, and C horizons from the land surface. The contents of the organic matters decrease from shallow parts to deeper parts of the soil profile. In addition, $K^+$ and $Na^+$ originating from the weathering of feldspars are dominant components among inorganic ions in the wetland soil.

• Tunnel and Underground Space
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• v.28 no.6
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• pp.569-583
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• 2018

The purpose of this study is to identify the collapse characteristics by analyzing various factors causing collapse based on field survey and existing data on rock slopes occurring in the construction of roads and industrial complexes in Gyeongsangnam - do area. In the case of the slope where the slope has been directly surveyed, the analysis of the collapse characteristics can be used for the prediction and prevention of slope failure through the continuous collection of the slope data, database construction, management and analysis. The evaluation items used in the collapse characteristics of slope were selected among the items that can be regarded as objective evaluation items among the overlapping factors by comparing the evaluation items frequently used for the evaluation of the existing slope stability among various factors. The type of destruction of the rock slope depends on the type of carcass of the bedrock, such as planar fracture, wedge fracture, onho fracture, and conduction fracture, which are different from each other. And the slope stability analysis should be performed accordingly.

• Journal of the Korean Geotechnical Society
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• v.40 no.3
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• pp.101-108
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• 2024

A system with the ability to recognize potential key blocks during tunnel construction by analyzing the rock face was developed in this study. This system predicts the formation of key blocks in advance and evaluates their safety factors. A laser scanner was used to collect a three-dimensional point cloud of the rock face, which was then utilized to model the excavation surface and derive the joint surfaces. Because joint surfaces have specific strikes and dip angles, the key blocks formed by these surfaces are deduced through iterative calculations, and the safety factor of each key block can be calculated accordingly. The model experiments confirmed the accuracy of the system's output in terms of the joint surface characteristics. By inputting the joint surface information, the calculated safety factors were compared with those from the existing commercial software, demonstrating stable calculation results within a 1% error margin.

• Economic and Environmental Geology
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• v.39 no.3 s.178
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• pp.235-253
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• 2006

We interpreted marine seismic profiles in conjunction with swath bathymetric and magnetic data to investigate rifting to breakup processes at the Korean margin leading to the separation of the Japan Arc. The Korean margin is rimmed by fundamental elements of rift architecture comprizing a seaward succession of a rift basin and an uplifted rift flank passing into the slope, typical of a passive continental margin. In the northern part, rifting occurred in the Korea Plateau, a continental fragment extended and partially segmented from the Korean Peninsula, that provided a relatively broader zone of extension resulting in a number of rifts. Two distinguished rift basins (Onnuri and Bandal Basins) in the Korea Plateau we bounded by major synthetic and smaller antithetic faults, creating wide and symmetric profiles. The large-offset border fault zones of these basins have convex dip slopes and demonstrate a zig-zag arrangement along strike. In contrast, the southern margin is engraved along its length with a single narrow rift basin (Hupo Basin) that is an elongated asymmetric half-graben. Rifting at the Korean margin was primarily controlled by normal faulting resulting from extension in the west and southeast directions orthogonal to the inferred line of breakup along the base of the slope rather than strike-slip deformation. Although rifting involved no significant volcanism, the inception of sea floor spreading documents a pronounced volcanic phase which seems to reflect slab-induced asthenospheric upwelling as well as rift-induced convection particularly in the narrow southern margin. We suggest that structural and igneous evolution of the Korean margin can be explained by the processes occurring at the passive continental margin with magmatism intensified by asthenospheric upwelling in a back-arc setting.

• Economic and Environmental Geology
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• v.54 no.6
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• pp.717-731
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• 2021

We analyzed the characteristics of the habitat environment for the Seonam study area in Ulsan, the southern shore of the East Sea using bathymetry and seafloor environment data. The depth of the study area ranges from about 0 m to 23 m. In the west of the study area, the water depth is shallow with a gentle slope, and the water depth becomes deeper with a steep slope in the east. Due to the right-lateral strike-slip faults located in the continental margin of the East Sea, the fracture surfaces of the seabed rocks are mainly in the N-S direction, which is similar to the direction of the strike faults. Three seafloor types (conglomeratic-grained sandy, coasre-graiend sandy, fine-grained sandy) and rocky bottom area have been classified according to the analyses of the bathymerty, seafloor image, and surface sediment data. The rocky bottom areas are mainly distributed around Seaoam and in the northern and southern coastal area. But the intermediate zone between Seonam and coastal area has no rocky bottom. This intermediate area is expected to have active sedimentation as seawater way. The sandy sediments are widely distributed throughout the study area. Underwater images and UAV images show that Cnidarians, Brachiopods, Mollusks are mostly dominant in the shallow habitat and various Nacellidae, Mytilidae live on the intertidal zone around Seonam. Annelida and Arthropod are dominant in the sandy sediments. The distribution of marine organism in the study area might be greatly influenced by the seafloor type, the composition and particle size distribution of the seafloor sediments. The analysis of habitat environment mapping with bathymetry, seafloor data and underwater images is supposed to contribute to the study of the structure and function of marine ecosystem.

• The Journal of the Petrological Society of Korea
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• v.23 no.2
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• pp.61-73
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• 2014

The dextral strike-slip Yecheon Shear Zone of (E)NE-(W)SW trend is developed in the Pukhumyeon-Pyeongeunmyeon area, Gyeongsangbukdo, in the central part of Sobaeksan Massif, Korea which mainly consists of Precambrian metasedimentary rocks and Mesozoic granite. This paper researched the relative formation time, the deformation temperature, and the distribution of ultramylonite zone of Yecheon Shear Zone from the analysis of their deformed rock structures and microstructures. There are the mylonite foliation and stretching lineation by shear deformation, and the (E)SE-vergence gentle plunging, moderately inclined tight fold defined by the gneissosity and mylonite foliation as ductilely deformed main rock structures. Flame perthites, myrmekites, microfractures, microkinks, kinkband, and undulatory extinction are recognized as characteristic microstructures in feldspars during ductile shear deformation. Patterns of c-axis fabrics of recrystallized quartz aggregate display single girdle and type I crossed girdle where the rhomb and basal slip systems are predominant. The shearing senses on sense-of-shear plane show top-to-the-NE and top-to-the-SW on the predominant NW-dipping and subordinate SE-dipping mylonite foliations, respectively. These characteristic rock structures and microstructures suggest that the Yecheon ductile shearing occurred under $350{\sim}450^{\circ}C$ deformation temperature after the tight folding. The (E)NE trending ultramylonite zone of Yecheon Shear Zone, which passes through the Pulnobong and the north part of Pakdalsan, is established from the zonal distribution of Precambrian metasedimentary rocks and the grain-size distribution of feldspars in the Precambrian metasedimentary rocks and quartzs in the Mesozoic granite.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.213-219
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• 2006

The Yongjang mine is located in Masan City, Gyeongsangnamdo, which consists of a black shale possessing quartzite veins with othercompositions such as gold, silver, and sublimated sulfur. The average width of the veins is $9{\sim}17cm$ and the average degrees of the gold and silver are 3.6 g/t and 113.6 g/t respectively. A regional and a detailed scale electrical resistivity surveys are conducted to determine the existence of the mineralization zones and the linear structures in the study area. In addition, surveys of a several different array methods are conducted such as dipole-dipole array in the surface and borehole-to-surface array, surface-to-borehole array, and dipole-dipole array in the borehole. The method of element division can be applied to the region in which the borehole is curved, inclined or the distance between the electrodes is shorter than that of nodal points, because the coordinate of each electrode cannot be assigned directly to the nodal point if several electrodes are in an element. Yongjang vein is extended longer under the subsurface than on the surface in the images reconstructed from the 3D inversion. Therefore, it is recognized that the 3-D interpretation of the electrical resistivity survey is a very useful method to figure out the existence of strike and extension direction because the mineralization zones and the linear structures are shown in each depth.