• Geophysics and Geophysical Exploration
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• v.6 no.4
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• pp.195-198
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• 2003

In this study, we have developed a 3-D visualization program that is helpful in the interpretation or comparisons of geologic and geophysical data, which have been acquired to understand the cause of ground subsidence in the residential area and to establish reinforcement strategy. The visualization program was developed under the Windows operating system for convenient use and easy understanding. It uses Visual C++ for the Graphic User Interface and the OpenGL for graphic handling. Since this program is user-friendly, even users who do not have the basic idea about GIS or CAD can get very useful information with this program. The applicability of the program has been verified by visualizing the real core log and resistivity tomography images obtained from the ground subsidence area. These results have shown that the program is very useful for comparisons of these two data for the interpretation of subsurface structures.

• Journal of the Korean Geophysical Society
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• v.9 no.4
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• pp.443-453
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• 2006

Using seismic profiles obtained in the Antarctic Peninsula continental margin around Smith Island located at the southwestern end of the South Shetland Islands, we investigated sediments distribution, sedimentation, continental shelf formation, and tectonic evolution history. The study area is a very unique area that has two tectonic provinces with a tectonic boundary near Smith Island just the landward projection of the Hero Fracture Zone (HFZ). To the southwest of the Island, the margin became inactive margin after the collision of the ridge crest of the Antarctic-Phoenix ridge and trench, whereas to the northeast the margin is still apparently active margin with the spreading center and trench morphology in the sea. Generally the northeastern margin has the shelf sedimentary basins wth thick sedimentary layers, well-developed forearc basin, broad continental slope and distinct trench morphology, and the southwestern margin is characterized by steep and narrow continental slope and localized shelf basins. the mid-shelf basement high structures are distinct in the southwestern margin, which are thought to be formed by thermal effect caused by the subducted spreading centers. The high is observed in the area just northeast of the Island, implying that the tectonic boundary along the landward projection of the HFZ is not sharply defined.

• Economic and Environmental Geology
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• v.9 no.1
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• pp.1-11
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• 1976

It is believed that geological survey, drilling and geophysical survey which was carried out on Tertiary deposits in Pohang is a valuable but through the studying of many Tertiary sediments in Japan discovered many questions on analysis of final report prepared by National geological survey. The main reason is: 1. The seismic sound velocity which have regulated in the final report prepared by geological survey for Tertiary deposits in Pohang was 1,500-2,000m/sec in spite of oil bearing sediments of same age in Japan are 2,000-3,800m/sec. These may means the requirement of reconsideration of seismic velocity for Tertiary deposits in Pohang and required to have a dipper drilling. 2. Stratigraphically, geophysically, and paleontologically, the Tertiary deposits in Pahang land area is similar with that of Nishiyama-Hunakawa formations of Akita oil field in Japan. Nishiyama-Hunakawa formation is the main oil bearing formation in Japan. 3. Those valcanic rock including andestitic rock and liparitic rock which have extensively distributed over either at land area or at sea bottom, assumed by geological survey as the base of Tertiary sediments. But in case of Japan many oil bearing deposits are in over laid by these kind of volcanic rock. Therefore a possible of same condition with Japan is presumable on Tertiary sediments in Pohang. 4. It is believed that the Tertiary sediments of land area in Pohang is the extension of offshore basin but is wandering that the final report submitted by geologic survey have not remain any word on report of ECAFE discribed so much problematics as followed: A. Although it was assumed that no great thickness exceeding 1,000 meters, or major structures would be encountered in the Tertiary offshore sequence, it was hoped that shallow hydrocarbon deposits might be found, because these sediment are lithologically similar to those of the same age in the producing area of the northwest Honshu region of Japan where hydrocarbon are extracted from depths of only 500 to 600 meters. B. Four possible hydrocarbon trap conditions are represented in the survey area: anticlinal folds, faults, pinch outs, along the igneous basement and lateral facies changes. C. Most of the prime possible reservoir area are beyond the 50 meter water depth mark, except for the structures in Yonil Bay. D. Despite the shallowness of the offshore basin, sufficient trap condition exist in the area to warrant further exploration for hydrocarbon. 5. All of the problems mentioned above have gave us a strong reasons to have us hesitating to make a final conclusion on Tertiary problems in Pohang, before to have a drill to a depth to 3,000 meters or more whatever it is the Tertiary or a Mesozoics below 1,000 meters.

• Geophysics and Geophysical Exploration
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• v.13 no.4
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• pp.336-348
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• 2010

The Single-channel seismic survey with the source of bubble pulser and drilling survey was carried out in 2008 and 2009 for the site survey of Daecheon-Wonsando area, which was a proposed area of Korea-China subsea tunnel. The goal of this study is to analyze the depth and characteristics of acoustic basement for the stability assessment and tunnel design in this proposed area through combining drilling data with this single-channel seismic data after detailed processing. For this purpose, among the data processing schemes which are usually applied to multi-channel seismic data, we applied the F-K filtering to eliminate the AC(alternating current) noise and the post-stack depth migration to produce depth section. As a result, we verified that the improved depth section could be obtained from single-channel seismic data, and the distribution and characteristics of basement could be analyzed in survey area through the combined analysis with drilling data. However, we could not interpret the detailed structures, fault and fracture zone, due to the quality of bubble pulser source and single-channel data. We expect that those detailed structures can be analyzed when higher resolution seismic data is provided. Therefore, we recommend some items for future seismic survey of subsea tunnel to obtain the high resolution seismic data.

• Economic and Environmental Geology
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• v.53 no.1
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• pp.45-69
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• 2020

In Danyang area, various geological structures as well as various lithology and strata are well developed, which are useful for studying paleo-environment and structural movements, and also typical karst landforms, wethering landforms and river landforms. If geologically and geomorphologically valuable resources are used in terms of geotourim perspective, it is expected that revitalization of regional economy through diversification of attracting factors and employment creation of local people. Danyang has many excellent geological resources for geological field trip, they can greatly contribute to the development of geology such as expanding the base of geology and cultivating successive generations. In this study, we have evaluated newly discovered sites and previously excavated resources based on academical and educational values. By using these geological and geomorphological resources, we suggest three geotrail courses as follows. First, Geo-trail A is mainly focused on geological structures (Route A: Jeong Hwan Route), where we can learn geological deformation and movement through various brittle and ductile deformation structures. Second, Geo-trail B is mainly focused on stratigraphic importance (Route B: Soon-Bok Route), which emphasizes on various rocks, strata and contact relationship. Third, Geo-trail C is mainly focused on geomorphological landforms and landscapes (Route C: Satgat Route), which provide information about different geomorphological landforms and the interaction between different geological agents. In order to operate these geotrail courses efficiently, installation of explanation boards and view points, cultivate local commentators, and visitor centers and experience programs should be properly prepared together.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1994.07a
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• pp.184-215
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• 1994

The Hydrogeologic data of 455 water wells comprising geologic and aquifer test were analyzed to determine hydrogeoloic characteristics of Cheju island. The groundwater of Cheju island is occurred in unconsolidated pyroclastic deposits interbedded in highly jointed basaltic and andesic rocks as high level, basal and parabasal types order unconfined condition. The average transmissivity and specific yield of the aquifer are at about 29,300m$^2$/day and 0.12 respectively. The total storage of groundwater is estimated about 44 billion cubic meters(m$^3$). Average annual precipitation is about 3390 million m$^3$ among which average recharge amount is estimated 1494 million m$^3$ equivalent 44.1% of annual precipitation with 638 million m$^3$ of runoff and 1256 million m$^3$ of evapotranspiration. Based on groundwater budget analysis, the sustainable yield is about 620 million m$^3$(41% of annual recharge)and rest of it is discharging into the sea. The geologic logs of recently drilled thermal water wens indicate that very low-permeable marine sediments(Sehwa-ri formation) composed of loosely cemented sandy sat derived from mainly volcanic ashes, at the 1st stage volcanic activity of the area was situated at the 120$\pm$68m below sea level. And also the other low-permeable sedimentary rock called Segipo-formation which is deemed younger than former marine sediment is occured at the area covering north-west and western part of Cheju at the $\pm$70m below sea level. If these impermeable beds are distributed as a basal formation of fresh water zone of Cheju, most of groundwater in Cheju will be para-basal type. These formations will be one of the most important hydrogeologic boundary and groundwater occurences in the area.

• Geophysics and Geophysical Exploration
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• v.11 no.4
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• pp.335-342
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• 2008

Electrical resistivity and seismic refraction surveys were conducted to investigate geologic structures and geotechnical characteristics of the subsurface, along with rock physical property measurements in Dokdo island. The survey results in Seodo island show that the fault adjacent to the fisherman's shelter is a normal fault and extended towards the NW direction, and that Bedded Lapilli Tuff in the downstream was more severely influenced by weathering and erosion than Trachy Andesite II in the upstream of the survey area. In Dongdo island, Trachy Andesite III and Scoria Bedded Lapilli Tuff were severely weathered and eroded, considered as weathered to soft rock formations, and their weathered zone becomes thicker towards the antiaircraft facility in the NE direction of the survey area. The study results also illustrate that Trachyte and Trachy Andesite are hardest, Massive Tuff Breccia is next, and Stratified Ash Tuff is the most soft rock in Dokdo island.

• The Korean Journal of Petroleum Geology
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• v.5 no.1_2 s.6
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• pp.27-35
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• 1997

The Gorae II area is located in the southwestern margin of the Ulleung Basin, East Sea and corresponds to the Ulleung Trough. The survey of 3D seismic data in this area was performed to delineate the structural leads confirmed by the previous 2D seismic data. As a part of 3D interpretation, basement related structural movements and their relationship with the stratigraphy were studied. The study shows that eight sequences were identified which are genetically related to the tectonics and sediment supply in this area. The geologic structures characterizing the study area consist of : (1) block faults developed in the early stage of basin opening, (2) late Miocene thrusts, and (3) Pliocene wrench faults. The eight sequences consist of pre-rift (acoustic basement), syn-rift (Sequence $A_1, A_2$), post-rift (Sequence $B_1{\~}B_3$), syn-compressional sequence (Sequence C), and post-compressional sequence(Sequence D) from oldest to youngest. The time structure and isochron maps were constructed for each sequence and also used in seismic facies analysis and interpretation of sedimentary environment. The interpretation results reveal that the relative sea level changes caused by several stages of tectonic movements and sediment supply control the stratal and structural geometry of Ulleung basin.

• Economic and Environmental Geology
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• v.48 no.4
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• pp.325-335
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• 2015

This study examined the possibility to extract potential alteration zones and lithologic information based on ASTER band ratio techniques for mineralized area located in ${\ddot{O}}v{\ddot{o}}rkhangai$ province, Mongolia, and the effectiveness of remote sensing as a preliminary exploration tool for mineral exploration was tested. The results of ABRLO, PBRLO, and PrBRLO models indicated that the detection of argillic zone requires the verification of the samples to verify hydrothermal alteration minerals as clay minerals can formed by weathering process, whereas phyllic-propylitic zones were considerably related to the spatial distribution of the intrusive bodies, geological structures, and ore distribution. QI and MI results showed that QI is more useful for sedimentary rocks such as conglomerate and sandstone than meta-sedimentary like quartzite, and MI faced relatively uncertain in detection of felsic or mafic silicate rocks. QI and MI may require additional geologic information such as the characteristics of samples and geological survey data to improve extraction of lithologic information, and, if so, it is expected that remote sensing technique would contribute significantly as a preliminary geological survey method.

• Economic and Environmental Geology
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• v.26 no.3
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• pp.311-325
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• 1993

The Ohto and Tohyun copper mine which are located 4 km southeast of Euiseong, Gyeongsangbukdo, Republic of Korea show various common geologic and mineralogic features. Both copper deposits are of hydrothermal-vein types, and associated with fracture system developed during formation of the Geumseong-san caldera in late Cretaceous age. According to structures and mineral assemblages, the mineralization processes have progressed in four stages: three hypogene mineralization stages and one supergene stage. Three hypogene stages are 1) stage I forming $N5{\sim}20^{\circ}E$ veins in the Ohto mine, 2) stage II building $N5^{\circ}W{\sim}N5^{\circ}E$ veins in the Tohyun mine, and 3) stage ill bringing $N80^{\circ}E$ veins which crosscut veins of the stage II. The vein ores consist mainly of pyrite, arsenopyrite, galena and chalcopyrite, minor or trace amounts of magnetite, hematite, pyrrhotite, stannite, bournonite, boulangerite, stibnite, galenobismutite, native bismuth, marcasite, geothite and malachite. The main gangue minerals are quartz and calcite. Wallrock is altered by sericitization, chloritization, pyritization, carbonitization and argillization. Arsenic and copper contents in arsenopyrite increase from stage I to stage III (from 31.28 to 33043 atom.% As) and (from 0.04 to 0040 atom.% Co). Going from stage I to stage III Fe and Mn contents in sphalerite decreases from 12.56 to 0.44 wt.% and from 0.24 to 0.01 wt.%, respectively. The compositional data of arsenopyrite in the early stage I indicate a temperature of $420{\sim}365^{\circ}C$ and sulfur fugacity of $10^{-6.5}{\sim}10^{-8.3}$ atm. Chalcopyrite and pyrrhotite assemblage suggest that Middle stage I was deposited at below $334^{\circ}C$. The compositional data of arsenopyrite in early stage II suggest a temperature range of $425{\sim}390^{\circ}C$ and sulfur fugacity codition of $10^{-6.4}{\sim}10^{-7.3}$ atm. Based on fluid inclusion the Middle stage II was regarded as to be deposited at $420{\sim}337^{\circ}C$ (Chi et al., 1989). Referring composition of sphalerite and stannite middle-late stage II seem to be deposited around $246^{\circ}C$ and $10^{-16.5}$ atm. sulfur fugacity. The ${\delta}^{34}S$ values of sulfide minerals in the Stage I, II, III range from 4.9 to 7.6%0 and indicate igneous ore fluid origin. Based on differences in mineral assemblages, chemical composition and chemical environments of Ohto and Tohyun mine its mineralization are considered to be formed at diffent mineralization ages and by different ore fluids.